If the car has ABS , bleeding may take special procedures. Consult the factory service manual for details, as this varies by all manufactures of cars.
THE WIKI covers this.
There are 5 ways to bleed brakes, and no ONE way is best, over the others.
(however, pressure bleeding is quite, fantastic, as is reverse pressure bleeding tool way)
There are Gravity bleed, 2 MAN, Pressure top bleed, Pressure back bleed, Vacuum bleed. (5 ways)
2 Man way or 100 years way, since 1914 racing cars and Duesenberg , stil works very well.
I will make the assumption of a typical car non ABS. With Calipers up front and drums in the rear.
I will assume the whole system is new and dry, and there are NO failures in the system, later I will show the tests to find failures.(and even AIR where it dont belong.)
All seals in the system are fresh and robust (what else?).
The Master cylinder piston is NOT restricted from returning to its home position ( opening the balance port)
The MC brake booster rod is setup wrong! Extreme danger ! Stop don't drive.
There are 4 reasons for bleeding.?
If you don't have a hard pedal, car keys in pocket, there is a problem.
- A Virgin system prime.
- The Annual purge.
- and removing air , from the system , after swapping parts (system was breached)
- Spongy brakes. (air in system)
Gravity Bleeding facts:
First of all, your system is a pressure system and was never intended to gravity bleed. Sorry, it was NOT !
Many cars will not gravity bleed. That is a fact, deal with that. (sorry air just hates to FLOAT down hill, dig? )
Many cars will do great up front, but not in the rear. (long pipes and vast places for air to hide, that too , is a fact)
Keep in mind at all times, that air wants to float up and the fluid will drain down and these 2 forces and cancel each other "Physics !"
CAUTION: ( I'd just bet, you'd want all the air out, right? , so you can feel the brakes hard)
Gravity bleeding does have merit to prime a dry system. sure. Don't let the MC go dry or it's all just a side show.
Do not fail to bench bleed a dry master cylinder.
Consider these ideas or facts hints:
- What works best for you, can be best for you, but any mechanic worth salt, can do them all , on call ! or FAIL! Ask any Pro? Use 2 ways, at least.
- The whole purpose, is to get a hard pedal. The only way to be assured (or a test?) of that is the 2 man , Pump-n-Hold.
- Air will get trapped, plan on that, some calipers have air traps. take them off , put in a piston blocker (wood or plate) and bleed it now, with the nipple at the top.
- Air can trap in a rear wheel cylinders, load compensator. (some have bleed nipples, do bleed there first, before doing rear)
- Always bench bleed the MC, (can be done on car, but eats the paint up , so.. that is your call there...
- After bench
bleeding the MC , do try Gravity bleeding first, just to prefill prime the system,
- Bleed from longest line to shortest , after filling MC. (first)
- Do not use DOT5 mineral oil racing,
fluid in your DOT3/4 car. PLEASE ! If you do , you will destroy seal's and that is dangerous.
- You can use the 2 man way , as a test to be sure you see no bubbles are exiting a nipple (x4) if none is seen and pedal is hard, call it a day.
Tricks?: Rap (hit) the fittings / objects (calipers) {backing plates?} as you bleed, to bump out bubbles.
Don't give up, do all wheels and fittings 3 times around the world.
The MC pressure bleeder uses a special MC (Master Cylinder) cap and has a pressure tank full of DOT4 and a hose.
The reverse bleeder tool, has its own DOT3/4 reservoir and a hand pump.
The vacuum method uses a hand vacuum pump and a special (comes with tool) bleeder tank that catches spent fluids. (pump gently try to avoid, vacuum readings, just move the fluid)
The pressure bleeder has the very unique way to get air past odd places in the lines from front to rear slaves.
Air seeks out high spots, this can help you or hinder you. (think HOW it can hide, look at YOUR system and see that.
Like slave cylinders with the bleed fittings not at the highest point?
I will not teach you to use each tool, my purpose is to show that there are many ways and some of the short comings, of each.
Each tool has a manual read it.
FPM = Forward pressure method
RPM = Reverse pressure method ( one of the best ways)
VAC = Vacuum at nipples (all)
2-MAN , one pumps and holds, the other cracks the nipple then closes , and yells, ok release the pedal (old school)
Gravity , Farmer John way, no tools but a wrench. (yes, has value!)
Issues or worries?: Rumors, fears, sideshows, comedy acts?
The cavitation
worry is a Red herring. I laughed for a week on that one.Yes, if seals are bad, do not use vacuum tools, but why are your seals bad. ? and point 2, why are you pulling a vacuum , stop that, and just move the fluid gently.
Yes, the slave cylindes (shoe brakes) are only designed for pressure, not a vacuum. So don't pull a vacuum , is that too hard to understand? Stay below 1 inch.HG, dah?
Using speedbleeders, makes the Mityvac tool work better, or use teflon tape on the stock bleed screws ends, so air don't suck in around the thread (fooling you there is air, when not).
I get almost all air out with my hand VAC tool, then go to 2 man rule, and now I have zero bubbles. Every time, with out failure.
Forced pressure method, Reverse pressure method, Vacuum, etc.
| Methods | PRO's | CON's |
| 2-MAN | Cheap , easy and very effective (old school wins) | 2 persons , none, after all we did this for 100 years. |
| FPM | Very good to excellent to perfect. but not as good as RPM | Costs
more but my DIY kit solves that. Can miss air in some places. |
| RPM RFI |
The Most perfect, in that it moves fluid in a natural way that is, air floats upward and so does the fluid ! | Cost. (slim chance to miss some air, "rare") OR DIY |
| VAC | Sucks fluid from the RES to the fitting. very good. | Cost and some claim it can suck air past seals. will not work well if lines are 100% full of air. Old seals in car may suck air. (a red herring) |
| Gravity | This is the drain and pray method, (has a purpose) Costs nothing, THAT it's forte' . Best way to start an empty system. Best used as priming method. |
Will
not get all air out of the system. In most cars and most of
the time. and is very slow and makes a huge mess.(due to long duration
with nipples open) |
The RPM/RFI tool will solve very hard to do vertical clutch bleeding or ?. Air floats and you will fail with out this tool.
Do not mix speed bleeders with the RPM (logger heads happens)
One alternate to the 2-MAN way. the ONE MAN PUMPER !
My tool for FPM
Links:
http://pstca.com/articles/bleed/balloon.htm
Best video that covers 2 tools in a short time.
http://www.youtube.com/watch?v=UJOemg5wAoQ
Bench bleeding the MC
http://www.cardone.com/tech-help/brakes/how-it-works-and-best-practices/master-cylinder-bench-bleeding-procedure\
Bleeding and be hard, (if all lines are empty for sure) and you may have to use 1 or more ways to get all the Air out.
The bubbles want to float up, so that will fight you all the time.
Don't forget: all line fittings end to end can be cracked lose and used to bleed air.
The same thing for Calipers , you can remove them and rotate them (nipple up) (pads blocked with wood or some shims) and get all air out of a caliper.
TESTS:
See ASE MASTER MECH, Duane Mariage's , how to find the air using real tests, not guessing. See the pinch test and MC block tests.
Elaborating on Duanes video above. you can pinch a flex line (no, don't do that old tired lines, fix them first) to find which slave has air.
As he said , (an ASE Master Mech) he pinched the Caliper line and the MC got rock hard , instantly. (the caliper is full of air.)
Blocks:
You can use old hard lines bent and pinched closed, to block the MC , 100% to see if it is bad (after bleeding just IT)
You can buy MC port plugs. if you dont want to make your own. You can test he MC on the bench before it gets put into the car.
Keep in mind , you can test each half of the MC 1 by 1. (not all at once.)
Warnings:
- Brake fluid will destroy the paint on your car! Take care not to spill it on paint!
- Brake fluid will destroy the blacktop coating of your driveway or ruin your painted garage floor. (not to mention the cars paint, ouch)
ver2 ----1-1-2013