Question: BRAKES: Gravity bleed vs. Pump and Hold

[73-81 BST]

Replacing calipers and flex lines
(VBP-CX Package - Complete O-ring Brake Kit with Sport Rotors and Hawk Pads).

Would like to know your opinion / experiences with gravity bleeding the brake system..


STW

 

[bill81vette]

When I put the new calipers on the '81 6 years ago,I had gravitied the fluid to the calipers,then pumped and hold when I was sure the fluid was at each caliper.
never had a problem since!!!
Good Luck!!!!

 

[muddywaters]

When I put the new calipers on the '81 6 years ago,I had gravitied the fluid to the calipers,then pumped and hold when I was sure the fluid was at each caliper.
never had a problem since!!!
Good Luck!!!!

On my 88 I wanted to change the brake fluid and that is exactly what I did.

 

[Rod75]

I'm a 'suction bleeder' with the mighty vac. Always worked very well for me. Never had the patience to gravity bleed.
I've had pressure bleeders also. But for me, it's just another tool that has to be refilled, drained and cleaned out after the job.
No matter the method, I like to use a piece of tubing over the bleeder screw to guide the old fluid into a container. I can't stand brake fluid running all over!

 

[Hib Halverson]

Gravity bleeding should never be the primary bleeding method on a '65-'82, or any car for that matter.

Yeah, it's a great way to start the bleeding process especially with a dry or near dry system (other than the master cylinder), but it won't get all the air out. The best way to finish the process is pressure bleeding. A close "second" is manual (or pump-and-hold) bleeding but with that, knowing the proper way to do it is key to success. Many people "pump" the brakes too violently and too rapidly.

Vacuum bleeding may work well if the calipers all have o-ring-type piston seals but it should not be used with caliper having OE-type lip seals because it's too easy to apply too much vacuum such that you suck air past the piston seals...which, of course, defeats the purpose of bleeding.

The last type of bleeding, "reverse pressure" (advocated by the people that make the Phoenix Injector bleeding tool) might work, but I've never tried it on a C2/C3 disc system.

My bleeding procedure has been the same for a number of years.

If I'm changing the master, I bench-bleed it first. If I'm starting with a full master but an otherwise dry or partially dry system, I'll put the rear up in the air with the tires off, then open both rear bleeders. I wait until both drip fluid before proceeding. Sometimes I gravity bleed the fronts, too, but sometimes not. Once the prelims are done:

1) Install pressure bleeder and pump-up to 25-30 psi
2) Bleed master
3) Bleed calipers RR, LR, RF, LF. I tap on the caliper with a hard plastic hammer while I have the fittings open. I bleed the RR caliper 2-3 times as long as the LR. I bleed the RF longer than the LF.
4) Reinstall the rear wheels, set the rear back down, remove the pressure bleeder, remove extra fluid in the master if necessary and road test.

 

[terry82]

I'm a 'suction bleeder' with the mighty vac. Always worked very well for me. Never had the patience to gravity bleed.
I've had pressure bleeders also. But for me, it's just another tool that has to be refilled, drained and cleaned out after the job.
No matter the method, I like to use a piece of tubing over the bleeder screw to guide the old fluid into a container. I can't stand brake fluid running all over!

i use a clear hose .

 

[Rod75]

i use a clear hose .

Ditto that!

 

[GTR1999]

I used most methods and really like the Motive bleeder I bought 7-10 years ago. Works the best for me and I have no issues bleeding brakes. Works good when you want to pressurize the system to check for leaks or to flush out old fluid. I think I paid $60 for mine, best brake tool I ever bought.

 

[Hib Halverson]

You gotta hand it to Motive. They have really marketed pressure bleeding to the DIY market and they've done it well.

There have been a number of small, non-bladder, bleeders on the market for a long time...I have one from Mac Tools which I've had for at least a decade, but no one marketed them very well to we DIYs.

Actually, the face on the pressure gauge on my Mac bleeder broke off and I'm sure the gauge won't last much longer that way so it's likely a Motive bleeder is in my future.

 

[SVO]

The last type of bleeding, "reverse pressure" advocated by the people that make the Phoenix Injector bleeding tool might work, but I've never tried it on a C2/C3 disc system.

I have the Phoenix Injector and it works well when you start with a dry brake system but you have to use a bit of a different technique with it. The rear calipers are no problem, due to having a bleeder screw on each half. The Injector allows you to fill each half with fluid. Starting on the RR, push fluid thru each half until you get clear fluid at the master. Repeat on the LR. The fronts are the problem, since you only have one bleeder on the inside half of the caliper. Starting with the FR, push fluid back to the master until you get clear fluid. Repeat with the FL. After you have both fronts done, go back and push fluid from the master to the calipers and bleed the FR, then the LF like you would with pump and hold. When pushing fluid thru to the master, you need to have the cap on, or you will blow brake fluid everywhere. Also, after about six pumps of the injector, you need to pull down the fluid level in the master to avoid overflowing the bowls on the master.

Up side, it allows me to do brake work by myself and end up with a nice hard pedal. Downside, is the price of the Injector. I wouldn't buy a Phoenix Injector strictly for brake work on a C2/C3, but if you ever have to bleed a hydraulic clutch, then it's a time and frustration saver.

Now for the $64 dollar question. If you have a dual master cylinder, where the front brake system is separate from the rear brake system, why is it recommended to bleed starting RR, LR, RF, LF? On a dual master, should it matter if you start bleeding at the right front or the right rear?