ENGINE  is OVER HEATING?:                                                                                     
A Fast index:
Frigid  engine or cab heater
A bad fan clutch Top  causes
Slam dunk solutions.
The rules /facts and theory's
Bad Radiator CAP?
Heat from where?
All signs of trouble.
All failures?
See they systems here.
Tools can find the cause.
Dash cluster heat gauge fibbing?
HOSES bad?;
 ACID or Electrolysis  damage
Got Bugs? "insects"
 Belts slip?
The Hill billy tests?
Didn't read the TSB yet?
Thinking in pure physics? (short list)


The Otto Cycle engine,is very inefficient, it wastes energy all time, at  about 80% of the heat energy in the fuel, is wasted. (gasoline/petrol)
The wasted heat (huge) is expelled 3 ways. 
(or 60% for Diesel)
  • The Exhaust system ( including the CAT)
  • The engine outer surfaces, are air cooled, and the transmission casing (conductive)
  • The Cooling system. (a major player here)
The cooling system expels all this extra heat, its job, is to expel, all remaining extra heat, if not, the engine will overheat.
This system, also regulates it, under  all engine loads and speeds , out door temperatures, and altitude (thin air cools less , thin & hot air is worst case. )
If the spark or cam timing, are retarded for any reason, that 80% waste, increases and this taxes the cooling system more. (cam belt slipped?, oops)
Always hiding in the shadows is, ("that straw, can in fact, breaks the Camels back")
Factoid's:  (I will call the engine cooling radiator the "RAD")
This car cooling system overheats at about 260�F {127
C} , using real instruments to do testing. (see chart of boiling points, and 4 other ways)
The top Rad hose must get hard at 180F stock hot Temp. (or the cap is bad or there are leaks somewhere ! inside or outside of the engine)
There must not be any  leaks in the loop, (Rad. seams or core, no leaks at any hose, or hose paths total end to end)
Note that 260F  is overheat point, and 226F and 242F and 212F are wrong.  The 3 classic fail points and one good. See that Good
Blue line below? 
The stock normal temperature is 180F at all times, in the  hot running engine.  (note the 80 degree safety margin)

Jargon?: RAD = Radiator, Cap  means the RAD cap , not the overfill side tank cap. AF = antifreeze coolant mix. STAT = Thermostat (a lazy typist)
When I say water?, that means 50% Antifreeze coolant.  We use this tool to check the percentage.

First are the easy pickings.
  • No leaks allowed !
  • With a dead cold engine, the rad, cap off the seen level must NOT drop, day by day, or you have leaks or the side overflow tank is bad? (the hose inside fell off? here?) or the cap vacuum breaker is missing/bad! WRONG CAP?
  • The dash gauge lies? (all do , it has no scale!) 
Use an IR  Pyro  temp. gun and hits over 250 to 270F or more?  (that is overheated)
Slam Dunks?:
(lots of possible evidence even before true overheat happens.)
  • Forgot to use Antifreeze at 50%? ( it's also anti boil !)
  • All looks in the system loop, shows that system is full of red mud? (time to do the full system flush, skipped at  2 year service points.)
  • Low coolant in the RAD neck hole, rad cap off ,dead cold., (look there first) got coolant leaks?, Rad levels drop every day.? (true levels, don't trust overfill tank yet)
  • Ignoring obvious coolant leaks on the ground or anywhere in the cooling loop system?
  • Fan belt slips? , fell off? or is shredded?
  • Try a new rad cap yet , very cheap to buy ? (can fail 3 ways)
  • A new Thermostat first?  like $15 total.  JUST Pocket change. these 2. Missing thermostat, wrong size, some joker used a 160F? installed backwards??
  • Zero full service? no full back flush of all coolant loop parts, and fresh, 50% Antifreeze? "do the 30k mile and 2 year service points" Flush and fill every 2 years.
  • Got leaks?,  ignoring leaks are you?  Time for new hoses, you think?
  • Passenger toes wet?,  2 hoses leaking there, I hope it is not the heater core is  leaking?.
  • Running only tap water as coolant, or that RED IRON ACID Sludge for coolant?"red lava for coolant?, and no fresh 50% Antifreeze?
  • Not a slam dunk, but the compression test fails ( a $20 tool)? (due to a bad head gasket) 1 hour labor.  but the gross engine misfire is as slam dunk,  (heard)
  • The side coolant overflow tank must not leak or explode with water/steam everywhere, that is ABNORMAL, and is caused by overheating or gross exhaust gas, incursion in to the  cooling system loop. (bad head gasket or far worse) The cause is not a slam dunk, but seeing it do that , is.
  • Seeing oil floating inside the  rad top filler hole? (or lots of carbon floating here?) Easy to discover Evidence is a slam dunk. (engine cold test)
  • Seeing, water in engine oil (looks like milk chocolate)  (more Evidence) same with A/T transmission dip stick tube , see milky ATF fluid there?
  • Green leaking from end of water pump? or at its tell tale hole  on front of housing? oops, that is a slam dunk. "the pump is bad"
  • Looking the engine head/block juncture, you see green juice, at the gasket seem?  ( oops?)
  • If you own a $20 spark timing light,  and the spark timing is like 25 degree's retarded? the cam belt did slip. and will make TONS of extra heat, this old cooling system my just over load. (1+ RAD tubes packed and bugs in RAD or A/C Condensor core?) Weak systems, do overload, in Failsafe mode or cam belt slip time.  All mech have this tool. so is a slam dunk,  5 minute check.  (or your buddy Joe timed the distributor by ear?)
  • Rad is packed in bugs and other junk? blast it out  with a water hose and nozzle, from rear to front works wonders.
  • The  Fan dead? (it slips on a hot engine?) see fan tests here. (overheats parked only?) The fan clutch prevents that from happening.

Rules , Hints , considerations, factoids , theories,  and laws of physics
Only 180
F and higher thermostats are allowed.
The dash gauge is a toy, if dead? ,fix the gauge or 1 pin sender               Use the IR pyro thermo gun, $15  to take real readings off the thermostat housing.
The dash gauge?  "it has no numbers on the dial, so is a toy grade !", No lie, if it pegs or wags, high and low, it overheated  and/or you have air below the thermostat.
Notwithstanding the RAD cap belching steam, sure it's overheated.
The can causes of overheating, can be easy or hard to fix, but  maintenance helps greatly.

If paranoid or anal?, run distilled water,  I use tap and got a million miles on engines, not one drop of scale in any, ever.  But, I flush every 2 years.
The coolant will boil over 270F (the back of the AF jug states that clearly)  This number is at sea level and under full normal 12 PSI pressure.
The boiling point of this mixed coolant is related to the 12 PSI (up to 14) system pressure, as pressure rises, so does the boiling point as does they type and percentage of the antifreeze and brand used.  Never mix brands/and types of coolant.  The Pressure is controlled by that spring in the RAD cap.
The boil over rating is printed on the back of all over the counter jugs of antifreeze. (it assumes your RAD cap is good)
Water does cool better, than pure antifreeze, so do not exceed 60% AF.  This is the graph showing the boiling points of the mixtures.

The hotter thermostats make the system work better, why?  "The EFFICIENCY if the RAD and the Engine, both improve"

By the way, a 195F STAT , increases radiator efficiency and a faster warm up, more cab heat and better MPG. (this seems counter logical but is based on the laws of Carnot.)
In simple terms, the larger the temperature differential between the air (flying over RAD) and the coolant , the more heat that can be extracted (boiling point controlled) from this liquid to AIR heat exchanger. 
So' if it's 120
F in Phoenix AZ., and the RAD water, is 195, you  have 75F differential, but with a  180F STAT, it's only 60F differential, The 195
F STAT makes the RAD more powerful. (can shed more heat) and maybe 1/2 more MPG?
Odd huh?  but is true. The down side, is if the rad cap fails. (boil point drops to 226F !)
But all new cars run 200F here in the states. So is common.
Some ECU's outside of USA (rumors) get upset if over 180F,  but no mine.

Acid damage is real. this damage  or worse.
The 30,000 mile Service points in the operators guide are stated:
If see signs of abused (red mud,etc) then a flush is needed. (advised)
Back Flush every path in the system, to be sure each path has full free flow, The IAC/ISC water path too, needs to be checked and must be free flowing. If these hoses clog the IAC goes, nuts.
The 1.8/2.0L engine has this weird water pump and thermostat, that if the small hoses to it, are clogged, the Thermostat goes quite nuts. (cycles randomly) All hoses here must be free flowing.
The 1.6L does not do not have this
temperature effect (at pump housing) but if the ISC/IAC coolant path is blocked, Idle speeds can/will be stratospheric.  3000 RPM?

All cars, with a dead RAD fan (clutch type or Electric) will overheat just parked idling in about 30mins (or so) ,starting dead cold ( not true, in winter in  Alaska or Nunavut)
The RAD on all cars are near useless parked, because NO AIR FLOWs! with no fan in operation, so the fan automatically (in some way) turns on, and prevents the eventual overheating of the engine. How and when, varies with all years, and makes, of cars.
Many old cars sometimes, are upgraded, that is, the clutch fan removed, and electric added and done so , in the wrong way, ( look for a bad, missing or wrong electric overheat switch)
I've installed many electric fans with a fancy summitracing.com inline coolant fan thermal switch, make this old car work just like new cars.
This is easy to test: 
If you use a custom thermal switch, make sure it turns on at the right temperatures.  (based on your thermostat rating).
Use about  20 degrees above the thermostat.  You want it to go active, just as the thermostat loses control of temperature regulation.

180F use a  200F switch.
195F use  a 215F fan switch. (adjustable thermal switches are best )
You want the fan on, just after the cars thermostat loses control of heat. 
For examples,  read new cars FSM for testing the fan switches, on some new cars there can be 2 fans and are staged, and as a rule changed  with A/C on !

I have also installed flex fans.  They are dirt  cheap and work.

To test the stock clutch fan (stock 89-98 car) see here.

Gobsmackme ? (old cars, you will see just about Any crazy thing, even wrong parts or missing)
Someone threw  away the fan ducting shroud?  (put it back) 
How do we tell a person that never saw a stock car  before, what to look for, on said car.?
Answer 1:  The FSM,  sold on fleabay for $15 bucks. (sold on any auction site )  The factory Service manual.

If the fan belt is loose, set it back to factory spec.

GOT TOO MANY BUGS (insects) in the A/C Condenser, or RAD packed in dirt (etc), and can not flow air, back flush it ,with a spray hose, these two CORES on the front of the car.

What does that side overflow tank, really do?:
Only the radiator top filler neck (cap off) shows true water level ,   the side tank, that overflow tank, that can in fact lie due to a hose inside missing or fell off.

Check the true level of coolant , dead cold only. (cold engine block) or risk painful burns.

If the the overflow tank goes dry?, then  the RAD will suck air, as you park car, and let engine cool.  (it's job is to collect the hot expansion, then allow the suck back action)
The "suck-back valve" is inside the rad cap
One more factoid (Physics):
Water expands  greatly heated.  about 7%  so 10 quarts becomes, 0.7 quarts (liter) more, or 10.7qt. expanded ;to the side tank goes the excess, this is normal. and sucks  back as the engine cools.
This cycle repeats over and over. (every engine heat cycle)
After doing 2 year service, on coolant, always burp the system and run engine through 2 heat cycles and then cold check coolant level a the RAD filler neck , if it drops this is common, until all bubbles leave the system.

Keep the side expansion tank about 1/2 full  cold. (read the OP. guide in the glove box for exact works and ways)

See Spring?, not gone via rust? not broken, feel the tension?, see the gasket, not cracked or missing? see the vacuum breaker (under persons nail), not wrecked, looks nice?.
For sure the most critical and cheapest to replace item, on this system. THE CAP.
Warning some new radiators do not fit the the stock RAD cap.  Not even a near fit.

Over heating is caused from only 2 reasons ( basic theories) 
1: Bad cooling system , or  2: engine is producing abnormal excessive heat
(both can  happen )
A normal engine does produce huge heat, in fact it wastes 75-80 % of the heat energy in the fuel.  The OTTO Cycle engine is not efficient at all.
This normal wasted heat expels, at the  Radiator and out the exhaust. (mostly)

The radiator is over sized about 50%, to cover this excess heat. (at full loads and speed, and hot days) and at top of Mount Evans Idaho 14,240 ft. (thin air)
If the Rad. tubes clog, this  excess capacity drops and the engine overheats, under heavy loads (hills, hot days, long traffic lights and for sure at Mt. Evans)
If the clutch fan fails, the RAD is useless at any traffic light or stop sign. (no air flow , no cooling happens, almost zero cooling )
The Radiator is sized for driving at full load, a 120F day (cargo with 800 lbs of bricks) and up a tall hill "Mt. Evans"  fast as you can go , using all 80-95 HP,  That is the goal of this system.

A Motor is producing too much heat  (a good cooling system can usually handle this, unless marginal)
( running in ECU FAILSAFE mode are you? or timing way off, either spark timing or cam timing belt slipped?)
A cooling system that is marginal can in fact overheat in in failsafe mode, or timing retarded.
This is because retarded timing overloads the water jackets with excess heat.  (and a loss of engine power to match)
This is a fact. (case in  point?, you have 2 clogged up internal RADiator tubes?)
Or both !  But it is a fact, that a good cooling system may hide all engines,that are running way too hot (FAILSAFE is the top way to get too much heat.)
My owners of cars, never know the cooling system is weak until one day that FAILSAFE rears its ugly head and bam.

A Coolant system failure.  (or marginal , driving W.O.T. up tall hills, it overheats?)  Jargon ... ?
or both.
(or a little of each, as Physic's proves and simple human experiments demonstrate )
The cooling failure means the Radiator is failing to expell enought wasted heat.
This is usually due to a bad radiator or there is tool low coolant flow (bad pump, or restrictions)
Some cars it everything wrong,  running pure water, system has red rust colored sludge for coolant and a pump impeller, that is rusted to almost nothing.

If the car only overheats parked, fix the fan clutch.

Always solve coolant loss first,  
(keep in mind boil overs , can cause  fluid loss, to the ground via the overflow expansion side tank) 
Coolant can only go 4 places: (ground, passengers feet, engine oil pan and A/T oil pan.) (oil looks milk shake colored?)
No coolant on the ground?
Hoses that are wet , dripping or cracked or squirting AF, are in fact bad. Fix those first.
If only the Radiator side fluid expansion take, leaks (cold levels were good) hot, then the engine may be bad, in 3 ways.
Bad head gasket , cracked head or block. 
Steam below is a sign of bad head gasket and warped head. (or worse; there is always worse to deal with)
Are you adding coolant every day to keep levels right?  Yes, means you have serious engine issues. (assumes side tank hoses are not missing)

Or steam from exhaust tail pipe end, HOT !!  (cold engines, the exhaust steaming, is NORMAL)

You found coolant on the passenger compartment floor? The core can fail and leak. So can its hose.

All Signs?:
  1. Green on the ground,? (or somewhere else?)
  2. Water exploding from overfill side tank? ( oil in RAD or Milky engine oil) Exploding gases, on cold start is bad head gasket or warped head or cracked head/block,  or just simple overheating, The Rad leak down test and the exhaust test (green/blue ) tests solve this riddle easy.
  3. Steam rising from hood or Radcap, or hose to Cap and recovery tank. Over heating or leaks.
  4. Dash gauge pegged. (or WILD GAUGE swings "air pockets below thermostat") or the gauge is fibbing?
  5. Motor pinging and loss of power.  (do not allow pinging, it will wreck the engine)
  6. Pistons landing on ground?  (just joking....)
  7. A/C dies?, does it?, due to A/C engine overheat switch ,tripping off. a 235 �F (spec) see FSM.  A/C means Air conditioner clutch dead.
  8. Does  the engine  over heat , if left idling a long time (30min-1hr). or only at stop signs or red lights?  (clutch fan not activating , check it, this way.)
  9. Does it only over heat while  moving ?  ( a bad pump, or Rad , cap or thermostat , in most all cases below.)
  10. Overheats, only on hills?  (bad RAD)
  11. Only overheats pulling or loaded with heavy loads ?
  12. Never overheats moving fast on flat ground.  (so the RAD fan is dead, no mater if stock"the clutch" or a hacked in Electric fan, it's DEAD)
  13. Do you have carbon or oil floating around in the Rad, filler CAP neck top tank ?  yes?, that is bad head gasket or worse cracked block/head. Do the Exhaust test.
  14. Overheats under all conditions, Catastrophic overheat.  ( can be bad pump (rotor gone) or RAD or system is packed up)
  15. Seems to overheat , even at first start , in 1min or less I have gases shooting into the overfill tank, that is a bad head gasket (mostly a warped head, at least)
  16. See Antifreeze (and water)  in the pans, Engine or Transmission.
  17. The  RAD fan running too slow, ?  800 to 3100 RPM is normal. Unlike other cars.  Fan check 
Cascade failures; Previous owner run car 10 years, with zero maintenance. and the cooling system failed, and the head warped and the gasket then leaked.
The failure was not the failure of the  gasket or engine or the Suzuki engineer , it was the owner. 
My point is , once you correct the failed collateral damage, the original problem still remains..   (eg bad rusted water pump impeller, clogged rad? , FailSafe mode, slipped timing belt. etc.)

BTW (by the way) we replace the pump every 60k with the new timing belt, their life spans are equal.
We change the fluid every 2 years or 30k miles, to get the ACID out of the block. (a natural process in all engines)
Running so called " life time fluid", is crazy. (run for ever) "more  EPA lies"

ALL Reasons for the cooling to fail:  
Motor is good. Vacuum near 19" HG at idle, compression in spec. 150 PSI + and timed perfectly. (did you check spark timing first?)
During a real tune up, the mechanic VALIDATES the above is correct. (as part of his service plan using a timing light (HF $20) "Harbor Freight)

A badly running motor can in fact dump huge heat loads onto the radiator. (a marginal cooling system will now fail)
BAD motor timing can and will cause  extra heat loads on the cooling system!  , so time you engine correctly.

No coolant leaks anywhere, be it the ground or the passengers toes.

Next is the Micro ways.  All the ways.  (some ways, are just overloading the weak RAD)
The cooling system can fail for many reasons. (some cars have 2 and 3 reasons, at once) Old cars, are mostly like this....
I will try to list them from easy to hard.   ( guessing can help with no tests done, and sometimes is necessary after the dirt cheap parts are replaced.)
The pyro gun can prove it is overheated and can prove a radiator is bad. ( dead tubes found)
So can a full reverse flush fix many a bad system  (a $15 DIY job or with  a new cap and thermostat)  after a pyro gun shows my RAD is ok, out comes the water pump.

True overheating , not just the
gauge reading wrong!    If you  have a bad gauge? , then do not trust it , but fix it now.!
  1. Running only water for Antifreeze coolant and not real 50% Antifreeze (it raises the boiling point of the coolant and is mandatory to use it)
  2. Poor antifreeze ratio  (the AF fluid raises the boiling point temperature of the coolant)  A 50% ratio of AF allows a 256F boiling point !  not 212F !
  3. Low fluid level   "look in actual radiator, cold, for actual level in the RAD TOP TANK !" (not the overflow tank, only the RAD level COUNTS)
  4. Coolant FLUID bad  (looks like red mud flowing?) (it does breakdown and turns to acid , and builds scale and coats critical parts)  Flush the system good.
  5. The front of the RAD CORE or between the A/C condenser is packed with bugs, dirt, leaves and junk , clean it out. (use a water hose and back blast it to front of car)
  6. spare
  7. Not keeping Rad full of coolant and the recover tank 1/2 full cold. ( Do not check levels of fluid, in a HOT system, ever)
  8. Air in the system , see #1  air on top of the engine, will make the dash gauge and thermostat  to go nuts, both cycling madly. The ECU will go nuts too.
  9. Fan belt is slipping, I use a hand held tachometer "optical"   FSM WAY page 6B2/3 , to see it slips or just Fan check belt tensions.
  10. Bad Radiator (RAD) cap , won't hold pressure or the vacuum breaker in cap, is dead. Replace the cap. The cap gasket must not be cracked. The is cheap , replace it.
  11. Bad RAD fan clutch , if car overheats at Red lights or up tall hills. (usually discovered in the summer or pulling a trailer) but not on flat ground moving fast.?
  12. Wrong thermostat used, bad, or missing? Installed wrong? I will elaborate a few below.
  13. spare
  14. Do not use paper gaskets on the 4mm deep well thermostat. Use RUBBER ring! in all housing with the 4mm lip, or it will fail.  << usually causes over cooling. (or chaos)
  15. Thermostat put in upside down (use wax side down 1.6L, wax right 1.8L) , the bleed hole must be at front 1.6L or at top 1.8L (up hill)
  16. The 1.8L the rear water line, on the pump must not be clogged. It this line clogs, the thermostat goes totally nuts, and cycles, in random fashion. (as does ECU/PCM)
  17. Bad water pump,  (the impeller is rusted away ) life is 60k miles, replace it with at new  Timing belt also rated at 60,000 miles.
  18. Inadequate cooling capacity  , that means the tubes in the Radiator are clogged, or  the water jacket are 1/2 full of RED MUD., use the IR gun to find this , so easy.
  19. spare
  20. A Bad head gasket warped head, or worse,  (see Exhaust gas found in the coolant tester)  tool test fluid goes from blue to green (fail)
  21. The water pump is sucking air in some way and Cavitates .  (bad o-ring behind pump or other very odd hose failure near by, or the pump seals are sucking air?)
  22. Spare
  23. EGR valve dead.   A very weak cooling system may fail, if the EGR is stuck closed. ( usually, it's 3 fails here added up)
  24. A good EGR lowers combustion temperatures, and lowers the heat dump to the RAD.  (a vary weak radiator can be overload by dead a EGR)
  25. Engine is running way lean.  Lean and bad EGR can cause pinging that you can hear, but all pinging dumps huge heat loads to the cooling system.
  26. Many times it is 1 RAD tube clogged, EGR dead, and 1 fin missing off the water pump impeller, and the ECU stuck in limphome, and 100 dead bugs in the front of the RAD.
  27. If the  Exhaust CAT converter is melted and clogged up , overloading the engine grossly and overheating  due to driver using full throttle and can't go fast, and RAD is tad weak.?
  28. A Cracked engine  block or head, bad head gasket , warped head, or worse.  (try a compression test, and see over 150 PSI warm to hot)
It is near impossible (at home) to flush a RAD to get the  rad tubes unclogged. Any pro radiator service shop can do this.
Bad antifreeze, caused this failure. Any RAD that clogs and or the cooling system has RED MUD, is a sign of zero service.

A Compression test or leak down (better)? SHOWS A BAD HEAD GASKET.

The top failures are: The system is simple. See it below?
  • Never serviced ever, or never flushed,  #1 all time cause.  Zero service at 30,000 miles /2  years, and the system is packed in RED MUD (iron oxide and acid)
  • No AntiFreeze mix at all, just water,  or levels too  low or running AF over 2 years.
  • Fan belt loose.
  • Rad Cap bad or not holding 12-14 PSI system pressure. (feel the top rad hose , feel that 12 PSI pushing back)?
  • Bad thermostat. (missing or wrong or wrong gasket , or upside down or not at least 180F rated.)
  • Clogged RAD tubes inside RAD. (and easy pyro gun test, hot)
  • A Bad pump. (it leaks?, is over 60,000 miles old)
  • Clutch fan not running 800 to 3100 RPM at all times, slow to fast engine.

Next we, review the systems and tools and special tests.

A common fail is using the wrong gasket #1 below , causing thermostat to go NUTS !
Click photo below to zoom it.

8V Motor

See this page for sources of thermostats, and the TSB.

The above manifold has 2 size Stat pockets, 1mm and 4mm , and the Thermostats are
NOT interchangeable at least must have special gaskets. 
The 4mm  type must have a large thick rubber o-ring or the engine will  never get hot.  "NEVER"
The below is the side SECTION view (x ray) of the thermostat housing.  
The below fiasco, causes Frigid running. or a thermostat that just goes totally NUTS ! read, totally unpredictable actions.

16v  1.6L Motor: (sorry for such crude edits, due to lazy and  me a bad artist )

SEE MY 16V thermo gram here.

1.8L Sport has  very odd reverse flow pump mounted thermostat.  (and the 2.0L I4 motor  too)
Both J18 or J20 engine have this oddity.
That oddness means, if the cab heater blocks up, for any reason, via pipe 22, the thermostat goes DEAD ! (or CRAZY) ! 
This design is very odd, Hose 22 blasts the STAT wax pellet, and most do so, or it all FAILS.

Odd, see water flowing to wrong side of wax pellet ?  Odd indeed. But is normal.
Make darn sure hose 25 on top flows end to end of 22 hose.
Make sure that tiny water port below ECT sensor is clear !!!

SAME below, see path 3, it must never be blocked, or restricted.

Factory schematic of J20A (2.0L DOHC) , similar motor to the 1.8L , in fact many part on it, are the same.
That O-ring below, must not be cracked or it may suck air and cavitate the pump.
The 1.8L and 2.0L water pump.  Thermostat is on left side (drivers view)

IR Thermo gun, or Pyrometer:   Dirt cheap and saves burned hands,  you can scan RAD tubes or exhaust tubes to find dead cylinders.!!!
IR = InfraRed (or to humans, heat)
(affordable by anyone).
You can do great things with this tool. 
Vast usage, even check all 4 exhaust ports for equal heat and if one cylinder is dead.  or dragging brakes (hot discs)
See if hot water reaches heater core and exits. hot. (clogged core tests) and RAD tube are clogged?

Professional mechanics have an IR Heat gun, that can look at the radiator core, hoses and Stat housing,  to find hot spots.

A typical  IR gun below:
Saves burnt hands and fingers,too.
Finds clogged up RAD tubes, or a bad thermostat.
   $20  HighTemp version,   ( they have a $10 one, too, at lower temp.)

Get the $20  one, so you can find dead or weak exhaust ports ! too.

My measurements with this device:  1991 -8 valve TBI motor.
After a new Radiator, all brass and new pump, hose and turned to perfection.
A new Dash gauge sender.
A new 195 Deg. F. Thermostat.

My Readings for my 8v motor.

click these below, to see 5 temperature readings.

Gauge       Stat      Top Tank      Bottom Tank  left,    Bottom tank right.

See here, for my 16v 1996 thermo gram data:  (short run and 50mile run)

I look at each RAD tube (core) for 50 degrees F , thermal drop.   Top to bottom,  (2 inches distance, from tanks)

EXHAUST GAS INGRESS TESTER:   Finds cracked blocks, heads or cracked head gasket  or  warped head. $40? tool.

Is Your KICK Over heating? , tired of replacing radiator, fan clutch, belt, and water pump and flushing to no avail.
Try this coolant exhaust gas detection device , below:
Liquid is blue, and goes green with exhaust contamination.  (to see it work as a test, run the hand pump with tool on exhaust pipe ,, motor running)
Get at any NAPA Auto supply. PN.700-1006
Finds Contamination in the coolant loop.
If this test fails , you have a bad head gasket or cracked head or block.  No more guessing. 

Can be used to detect EARLY failure (before you notice overheating).  Do this before a 3000 mile trip.
About a $40 tool.  At Napa stores USA wide.

If you are brave you can use a $4000 5 gas analyzer to sniff the rad cap opening, but if you get some fluid, kiss off  that fancy .

Serious Overheating:  (Block and head )
Got Signs?
 (steam blasts, water gushing from side tank, carbon in the RAD filler neck , cap off dead cold engine,?  water in the engine oil, oil in the RAD filler neck or water in the A/T transmission (any of the dip stick ends are milky), dash gauge, pegged to Hot.
Steam exits the exhaust tail pipe end all day long?  

More Bad signs:  besides, water on the ground (green ,orange or pink)  (find source of leak first,)
Radiator keeps loosing coolant, every day? (magically goes away)

You may have a bad head gasket or cracked head or block or usually a WARPED HEAD.
You can do all these tests to find the cause.
See this tool and how to find leaks in combustion chamber HERE.

This tool can find the exact location of leaks, to the block, water jackets, intake tract, valve cover? etc.
Using a simple rubber hose to my ear I can hear the leakage path. 
At intake port?
At valve cover oil filler hole (off)
At jackets , water pump off.
At pan, drained of oil, and listen at drain hole opening.
or even walking a hose  the circumference of the head gasket. 
A very power full tool, just  using the air hose at spark hole, only, you can do that.
These facts (evidence) you can make an informed decision, scrap or rebuild engine, or gee it's just a cracked head.

Dash Cluster Coolant temperature Gauge:
Dash gage for coolant temperature reads low , high or funny (goes up then down, repeating).
Low: Bad thermostat or its too cold outside , so block the radiator, or some bone-head  took out the thermostat. Wrong Stat gasket.
High : all the above, under serious overheating.
Funny:  Coolant is low so the sensor is not touching the coolant ,thus the funny readings.  Burp the air out of the system.

Last: never trust the dash board gauge readings of any car,but here is how to test the gauge.

Read here the many reasons for funny gauge readings. (Varying or Frigid !  ,not overheating,)

Get an IR temperature gun and take real readings.  

Dash gauges are very inaccurate devices.  Most OEM gauges are cheap inaccurate devices.  (please note, no numbers printed on the gauge!)

This can also be done with an old fashioned mercury thermometer, or a Turkey/ Roast meat thermometer.
They sell accurate meat thermometers today, that are digital and are dirt cheap,  $3.00 at most Ross stores.

Take real readings, with real instruments and you will never be sent down the wrong path. 

Once you know how your dash gauge reads , against a real thermometer, then you have some idea, about what the dash gauge really means.  
Please do NOT let that cheap OEM gage lie to you.  Just take a real reading.  It has no numbers on the scale , so it's just a toy. (mostly)

Here is a cheap way to do this validation. ( < $20 way for the really cheap skates of the world  and it has some risk )
Old School way, no IR gun. (not recommended, I put this here for completeness)
Steps:  I never do it this, I use only an IR HEAT meter GUN !
  • Cold engine.   
  • radiator cap removed.
  • insert a real thermometer into the neck of the Rad. cap hole , and submerge the tip into the liquid.
  • start the engine and let it come up to full temperature at idle.  10-15 minutes.
  • some fluid will leak out as it gets warm , this is normal  expansion (provide a catch pan).
  • now read the instrument and then go inside the vehicle and read the dash gauge.
  • the Real instrument will read about 170 to 195 Degrees F.   Note the dash gauge reading.
  • Keep this reading in mind so you now know what the correct temperature should read.
  • Kill engine quickly after the test, so you don't lose to much coolant.
If the Temperature goes above 200F by much, there might be a problem.

Some cars have an electric fan and it will come on shortly after 200 Degrees.  It it does not , it is bad.  225 degree's is common value.
Most Sidekicks have a Fan clutch. 
The sidekick condenser fan only comes on with A/C , and only if the A/C amp module, allows that to happen.

If you must throw parts, throw in a cheap thermostat.

The best tool of all, is that cheap IR gun, get one and you will be very happy.

IR = infra red Heat measuring Gun.   Contact less, no risk , fast and accurate ! 
The first burned fingers you  save, using this gun will pay for the $20 asking price.

Harbor Freight ships world wide (mostly),  buy one before you need it !

Finds leaks no matter where they are:   

Do a radiator coolant leak down test.   (cracked block /head,.etc ?)
You pump it up and if you see green, bingo a leak you found, the do the leak down test. if it fails and there is no green on the ground, it must be leaking inside the engine or the A/T cooler section. (drop the cooler line see green?)
 Finds cracked heads, and blocks and head gaskets.

If this test fails, the loop is breached.  No guessing.
Only question is where.?
If  motor don't leak to the ground then the leak is in to the engine,  switch to water only as coolant ,before more damage happens.
See the Tachometer tool here:

The below is a bad pump the impeller is gone,  but IT IS NOT THE PROBLEM, IT IS ONLY A VICTIM .
This is electrolysis damage,  a bad ground wire in the motor bay, caused all Alternator charge currents (ground side) to flow through the Pump impeller killing it dead)
If ignored, IT WILL REPEAT:    This guy had the starter wire not at the Starter mount bolt ,like new, but on the frame.  This is why it died.
By careful examination, you can see its not AF acid damage,  Acid eats every inch of all the parts.  This is from a 1.8L Sport.
There is this real cute test for this,
Take cap off the RAD,  put DMM on 2 volt range (low) and put minus lead to battery minus lug, then insert the read lead in the rad neck and into the liquid, not touching the sides of cap well and take a reading, you are seeing if the RAD and liquids form a battery. Natural Acid polluted AF can do that. Zero maintenance proof.
less than  0.100 volts is good
over 0.200 volts is bad,  replace the AF.
Bad antifreeze can destroy the pump, (see below) the radiator from the inside out and eat through a perfectly good head or head gasket. See last photo below.
This is DOUBLE ACTING damage the ACID eats the parts and the ACID forms a battery and the battery action (electrolysis ) removes the metal 1 atom at a time.

RAD = Radiator, AF = Antifreeze, DMM is digital multimeter...
Ignore this, and it will repeat. This engine had a bad GROUND strap.

Acid and Electrolysis damage (head can be etched too)

The two cheap parts, pump and gasket , are the least of the damage that can happen, with zero maintenance.
The head can be badly damaged. 

The Fan Clutch: Most 1989 to 98 Suzuki Sidekicks use an AiSiN FCS-001 of Japan part, same maker at the A/T 4speed tranny.
You are here because engine overheats parked, and never running and moving car fast.
 I prove overheating with a real IR pyro gun first. 
at near 270F + is overheated.
Mine runs at 200F all day every day (a 195F STAT in its housing)
Suz. P/N  17120-57B01  fits 8v  and 16v.
actual photo.
It is a thermostatically /RPM controlled device, that when operating normally, will vary the fan speed independently of the engine speed.
I use this tacho tool.  $15

If the engine does not overheat with car moving fast, the clutch here, is the probable cause, and is a bad fan clutch hub.
Keep in mind, at idle, that there  is no natural air flowing past the radiator core (car is parked),   and all cars overheat, when hot idled and the fan is dead.  (not in Alaska,....)
Never touch the fan, with your body parts, on a running engine.  The rolled up news paper test is mostly not definitive. RPM IS .
The only test that matters is the below FSM  test, the official Suzuki Factory Service manual using a hand held RPM Tachometer is the test method of choice. (and IR Pyro gun helps)

Cold engine and for sure, not running,
Open  the hood.
  • the clutch is not oozing Silicon grease, if you see signs of said internal grease the clutch is bad.  (bad seals and usually the bearings)
  • I Jerk the hub by hand, in odd angles, not turned, if the bearings are so bad the fan moves independently from the shaft flange, the hub is BAD. (bad bearings)
  • The mechanic calls this  bad axial or radial play in the bearings. He then spins the hub by hand engine off to feel if bearings are GRINDING. (all are bad clutches)
  • He then spins the hub, rotated, and must be free  or the clutch is seized up.  it's a bad  clutch hub.
  • If the clutch makes noise,  turned by hand or running  the engine, it's is bad.

Engine Start engine, cold.  Open  the hood ,
  1. Make sure fan belt does not slip. if it does, set the belt tension pre factory spec. using the alternator , adjuster top bolt.
  2.  verbatim FSM words next then comments,  RPM tests are the FACTORY way. (using and optical tachometer saves you injury too.)

Comments, see step 1, see the word Regardless?  If this step fails, #1, the clutch is bad.
So, if engine overheats, parked, at idle and the fan is not running at full speed, then the clutch is in fact, bad. the Fan clutch.
There are 2 or  3 kinds of  fan clutches, RPM based, Thermal and a mix of the 2.
The Suzuki clutch is a mix.
Suzuki nor the maker sells internal parts. Nor do the have spec.'s for the internal parts, of any kind.
Other cars , uses different clutches, like Toyota, and others.
As they say, "this is not your Fathers Oldsmobile", nor moms , Toyota land cruiser, sorry, it is not.
  • SLIPS FOR easy engine starts, From say 0 to 500 RPM (  (est. as no spec. published)
  • Then engine starts, and runs and is connected and runs at cooling pump RPM, at idle. (even at 800 engine RPM)
  • When at 131F the clutch starts to slip ( contradictory to logical thinking and to many other cars !!!)
  • Then when RPM is too high for the cheap plastic fan the fan limits, Fan RPM. per rule 3 in the FSM.
  • This fan wastes energy, and is not GREEN.
Unique to Suzuki?
note the Suzuki fan pulley smaller than the crank pulley,  that means the fan will spin faster that engine RPM,  my guess, is  engine 800 RPM  gives fan 1000 RPM (at idle)
The plastic fan on this engine will/may/can , explode if RPM is not limited to 3100 RPM pump RPM.
That fact, plays as a key factor in the design and operating actions of this  clutch device.
The Fan is not rated to max Engine 5500 RPM, in NO WAY is it.!  The fan pulley runs about 20% faster too.
If the clutch is too expensive  $60 to $100?, remove the fan and put in a used dirt cheap electric fan off a wrecked newer car, with a switch and inline fuse.
Be sure to turn off the fan switch, when FORDING streams
or install a cheap flex fan.
 Sold in just about every car store on earth. (a generic part) but needs and adapter to fit this car.  Good luck finding that.

Rockauto.com sure does sell this clutch and is not very expensive considering the quality and complexity of the device. 
AISIN Part # FCS001 at $56
Suzuki calls out just 1 clutch ) from 1989 to 98, now SUZ. P/n #17120-57B01 at $210 (2014 price)
G16A/B ONLY.  the J18/20 engines all use a different part.
Shipping and taxes and import duties all increase costs, not to mention down time? , so buy locally and save.
Crossovers? (not official)

NAPA AUTO has it for $41 bucks.
ATM 1563504

If this clutch SEIZED, and you are in ALASKA, the engine Radiator will overcool in winter.  (some, so bad, they put cardboard blocking 1/2 the Radiator core)

TACHO TOOLS:  This device , sends out a red laser beam (LED) and reads RPM of just about ANYTHING.
A hands free tool that keeps hands out of danger, from a distance.

$15 bucks.  I paint liquid paper (Office depot) on the fan hub and point this laser, and mark the water pump pulley too. (vast usages)
I use the same tool for setting idle Dutycycle (FSM steps). , or to witness belt slip.

My SUZUKI factory hose list for most G16A/B engines made.

Hoses are different by TBI , MPI, and A/T , and M/T , these are Suzuki part numbers and MOST, are all still sold at Suzuki.
As seen here.

Hill billy time?, ( or far from home?, way OFF ROAD? or at Aunt Milly's?) and want to do wild and wolly tests.? (lots of water on hand)
  • The first test is to see if the water pump works,  I take off the thermostat housing, and STAT, out of its hole, and I'm looking at the top of engine water jackets (effectively) and pump output . (at hole)
  • I crank engine over , sparks wires pulled, see the pump action, water flowing fast out of the housing, yes?, the pump may be good, (this is the totally rusted to nothing impeller test, & dead pump)
  • I put back the STAT housing sealed with a gasket and no STAT inside, filled with water , I start engine (spark wires back) with cap off, RAD.  dead cold engine In all cases.,  I look for bubbles
  • to reach this RAD filler hole,  lots of bubbles may be carbon, may be oil.  If yes the head gasket or worse is blown. (cracked cylinders, or head.)
This second test, done cold lets you find evidence, that can not be seen on a hot engine or with stat  closed, dead cold. (it's a dirty trick doing this) see?
This is done because (only) you do not have the 2 tools that find this failure,  the RAD leak down pressure gauge, nor an exhaust found in cooling tool.  (green blue, test)
Nor the 3rd tool that can find this, a cylinder compression test tool. (a blown head gasket or worse)

If done dead cold engine, this test is safe. (no damage to engine) (test times short, 2min or less)

In Pure Physics:
Then expanded a bit.  (Coolant loop failure? The coolant loop  can not flow normally ?,  or Air is not flowing through the Radiator core?) <(just 2 fail paths here, easy huh?)

It leaks fluid? , correct that first. ( onto the road or passeners toes)
No Antifreeze in the water, running pure water, or over 60% AF?  that be wrong !
Low coolant levels in the actual radiator ?  (not side tank  the actual radiator checked cold engine !)
If the coolant is low or the coolant leaks out driving unseen or parked, the system will overheat,  (air in the engine block loop is useless, this engine is water cooled. )
The Rad cap must hold at least 12 PSI (near 1 bar) pressure and the top radiator hose must get HARD, hot engines. (if not?, your system loop is BREACHED, some where)
If all this is ok,  then the loop is not flowing correctly, a pure physics deal.  Flow. To have proper flow in all radiator core tubes,  (many) all must flow freely.
The thermostat must not be stuck closed. (or flow stops dead)
The Water pump impeller must spin at full speed, ~1000 RPM min., and the impeller must not be fallen off (rebuilds fail that way) or rusted to nothing gone.
Over heats only parked, might be no air flowing through the  RAD core, due to a dead fan, or bugs in said core.

Data: note3:
Keep in mind the following facts:
The air conditioner will shut off  when the engine coolant hits 235 �F and the boil over point is 265� F.. (15psi + 50% glycol)
The A.C. has its own engine overheat thermal cut out switch, and is totally independant of the ECU/PCM.

rev 18  , ,   9/28/11 and more signs, list.  11-11-11 added last pump and head gasket damage.  v17 -10-10-13 , new Rule section
 10/15-14,  more edits.
added new chart and hillbilly section. 2-24-2015  and more slam dunks...