Bleeding the Brakes

[Bye 87GN]

Guys,

After getting my new engine in, I promptly blew a brake line on the rear axle and all of the fluid leaked out. I replaced the lines and went to bleed the system (vacuum setup). I seem to recall something about pressing the button on the front of the proportioning valve to allow bleeding, but I can't find any info about that here when searching about bleeding the brakes, plus the button does not seem to want to move.

Anyway, the rears will not bleed via gravity or mighty vac, so I'm guessing i have to do a better job bleeding the master cylinder vs. opening the lines at the side of the MC and letting fluid leak out.

I would imagine my process should be:
1. bleed the MC with a bench bleed type kit
2. crack the lines at the proportioning valve to be sure that's set
3. then bleed the brakes as normal (right rear, left rear, etc.)

Any one have info on the proportioning valve deal, or idea why the rears won't bleed other than the above?

Thanks.

 

[zeus87gn]

After you bench bleed the MC, you shouldn't have a problem with the rest of the system. You have to get all the air out of it or you won't ever get the fluid to the wheels.

I have heard about the valve button also, but never messed with it. And never had a problem. I would like to hear others chime in on this also.

 

[85TurboTtype]

Yes, you shouldnt have to mess with the proportioning valve. Ive done rear brake lines on 2 cars now and havent touched it. Alot of guys think that the car has to be on while bleeding too!! To tell you the truth, you will build up more pressure when you have the car turned off. I tried for an hour before a buddie of mine came over and told me to turn off the car. After the car was off, it took 2 separate pumpings of the pedal and I was getting much better results! You will need 2 people for this of course. Leave the car off, and start with the farthest point from the master cylinder. Right rear wheel cylinder, left rear cylinder, front right caliper, front left caliper. Even if you just did the rear lines, make sure you bleed all of the brake points. MOST IMPORTANT!!! Make sure you keep fluid in the resivoir!!!!!!!!!! It may look like its full, but its probably the black boot sucking into the resivoir. Dont bleed the brakes with the cap off of the resivoir either. Fill it and cap it every time!

You can also bleed where the long rear brake line meets the 2 small lines. Just unscrew it and retighten before the brake pedal is let back up. I would only do this if you are having problems. Sometimes an air bubble gets stuck there, but not always.

 

[Bye 87GN]

Follow up

Just to let you know, I could not find any bench bleed kits anywhere, but I did just crack the lines at the MC and the proportioning valve and let them gravity drain for a while. After that I cracked the bleeders on the rear and got the driver side to start to bleed. The passenger side would not go, so I cracked the supply line at the cylinder (right rear) and let that sit for a while and it finally did gravity bleed, but the bleed screw still did not let anything out. I decided that the problem had to be in the cylinder. Possibly it was in some wierd off-center position, so I tightened everything up except the bleeder and slowly depressed the pedal. The pressure from the brake fluid finally got into the cylinder and re-centered the pistons and that allowed the bleeder to do its job. I think I'm all set now.

Thanks for the help.

 

[Bye 87GN]

BTW, I never did have to do anything with the proportioning valve plunger thingy. I just waited until I knew I had fluid at the valve and pressed the pedal a few times to try to get the valve re-centered. I'm not sure if the gravity bleed worked or the pedal pressing worked, or a combination of the two. Since my car has brakes again, I don't really care which one did the job...

 

[zeus87gn]

Good to hear you got the fluid going.
It usually takes some persistance when you get a difficult cylinder.

Strange, another fellow I discussed brakes with said he couldn't find a bench bleeding kit either. I will have to ask the next time I am at the 'Zoo' or the other parts store here in town.

Happy braking!

 

[85TurboTtype]

Ususally the bench bleed kit comes with a master cylider. If not you can make one your self. All you will need is 2 small clear pieces of hose and the two fittings that go into the master cylinder where the brake lines would go. The pieces have tapered tips so that the hoses will fit tightly to them. You can get a clip to hold them, ie. Spark plug wire clips or something simialar. You just need to make sure that the hoses stay on the tips and in the fluid in the resivoir. Then SLOWLY pump away at the piston that goes up the middle of the master cylinder until you see no bubbles comming through anymore.

 

[spudmanmike]

Its funny, i've always bled the master cylinder with hoses routed back into the reservoir like mentioned above. I put one in a couple weeks ago and bled it by putting plastic plugs in the ports and pumped it for a couple minutes (per the instructions). Works great now