Blown head gasket

[SKwane]

Bad head gasket symptoms I have: '89 Sidekick 1.6-8V

-White smoke from tailpipe.
-Coolant loss.
-Compression (hot): 160-150-145-145
-Leakdown test: 1&2 are at about 12%.  #3 at 16% and #4 at 21%.
-No bubbles at radiator neck.
-No coolant in drained oil.
-No visible leaks of coolant on engine exterior.

My question:

How do I make sure it's not a cracked head or block?

[fixkick]

revised, it was not sMOKE it was steam at tail pipe end.
steam there is coolant, smells sweet , not smell like burning oil is a huge clue. (but both are possible if very unlucky)


white smoke can be just PVC clogged,or bad intake valves seals bad sucking in oil like mad.
what tranny here, 5sp M/t that year i bet but if 3speed, no AF50% into the box. and now milky ATF
sorry I am so slow. I will try harder.

the harbor freight , rad pressure leak down tester works great, has hand pump, so stoke it to 20 psi and watch it for not leak down.
no water leaks at passenger toes rug soaked in AF50% antifreezed
no running pure water are you.
new thermostat 7years old or newer?
no oil floating in RAD neck dead cold
no carbon chucks floating same place.

get engine fully hot, even 10 miles hot
park and hood up and look for any leaks. every inch engine/hoses.
new rad cap too. they have a vacuum breaker that can fail. too.

[SKwane]

rad pressure leak down tester works great, has hand pump, so stoke it to 20 psi and watch it for not leak down.
no water leaks at passenger toes rug soaked in AF50% antifreezed
no running pure water are you.
new thermostat  7years old or newer?
no oil floating in RAD neck dead cold
no carbon chucks floating same place.

get engine fully hot, even 10 miles hot
park and hood up and look for any leaks. every inch engine/hoses.
new rad cap too. they have  a vacuum breaker that can  fail. too.

It's a 5-speed.  Running 50% AF, no leaks from heater. 

I checked thermo operation several times and it opened just at right temp (195 or so checked with IR gauge). 

No oil in rad at all. Didn't really check for debris in rad.  It was newer AF and pretty clean.

I removed head and found a hairline crack between #3 and #4 and evidence of coolant going mainly into #3.

I followed the info at the link below and cleaned the crack with brush & carb cleaner and forced JB Weld into the small crack as best I could. It set up for 2 days before I installed the head with new gasket. Used the old head bolts:

https://www.2carpros.com/questions/1989-...gine-block

I didn't have a good steel rule to check head warpage, so it may be a bit over the .002" limit.

Was pressed for time and busy with other stuff so have only driven it about 30 miles and it didn't overheat.

I'm not able to check it out until October or so, since I'm out-of-town.

[fixkick]

"I removed head and found a hairline crack between #3 and #4 and evidence of coolant going mainly into #3."
AT HEAD OR BLOCK.? ( THE HEAD CRACKED IS EASY FIX TAKE IT ANY HEAD MACHINE SHOP AND TOWN AND POINT)

JB weld is really just cheap epoxy. glue. (THE WORD WELD IS A HUGE OXYMORON NAMED)
epoxy hates heat,oil/water and pressures huge here. (YES VASTLY BETTER EPOXY ARE SOLD, ASK)

combustion pressures are huge. 2000psi possible under load huge(hills) and aggressive right foot. (OR A TRAILER FULL OF BRICKS)\
AS ARE COMBUSTION TEMPS HUGE. (The reason the shop said (link) forgetaboutit.
yes may work for a while. (AKA, band-aid )
no photos of crack.? block or head.?

so was not smoke at all,but steam at tail pipe, a huge give way evidence that.
SORRY FOR YOUR LOSS!
FINDING ENGINE BLOCKS NOW (IF IS) ARE NOT EASY . TOOK ME 6 MONTHS TO FIND ONE IN 2008.
BUT CAR-PART.COM YES TRY (WRECKERS NET)