New EVERYTHING. Brakes STILL soft!

[JFH]

Just another suggestion, I would not use a rebuilt MC get a new one there not that much more.

JFH

 

[NJTurbo]

Originally posted by Red Regal T
I've been reading this and although you replaced the master cylinder, that's what it sounds like to me. Do the brakes pump up when the pedal goes low? Anyway, I'd think about trying another mastercylinder. You may have got a defective one.

Red thanks for answering the page

 

[granitestategn]

Bench bled?

When you said you bled the MC, I assume this means you bench bled the MC with it horizontal prior to installation. When they're installed, they're on a bit of a tilt. I don't know if that traps air or not. I bench bled my MC until my arm was tired from pushing the plunger. I had to do it twice because I didn't get all the air out the first time. After bench bleeding and installing, I cracked each fitting at the MC and bled it in the car. It was good after that. BTW, I got a recall letter from Buick way back when and my car was bought in Rochester, NY. It must have been around 1990.

 

[gmgearhead]

brakes

hello,take it from me..you need a proportioning valve..!!!!
i have a vacume conversion same as you and had same complaint.I replaced everything...same problem exsisted.
Changed to new style brass valve and bingo,awesome brakes..!!
hope this helps and saves you some money..!!
Walter

 

[SPOT MY 6]

Well I finally found time to take the line lock out of the system and re-bleed the brakes. This time I gravity bleed the front brakes for 40mins per wheel. I didnt bleed the rear brakes since I never took the rear brake fitting off of the master cylinder and there was always fluid in the MC.

Nothing has changed. They still go right to the floor. So I've narrowed it down to either:

1.) The factory brake proportioning valve
2.) Bad or wrong rear wheel cylinders
3.) Bad master cylinder, even though it is a remanufactured unit with 100 miles.

 

[NJTurbo]

Originally posted by SPOT MY 6
Well I finally found time to take the line lock out of the system and re-bleed the brakes. This time I gravity bleed the front brakes for 40mins per wheel. I didnt bleed the rear brakes since I never took the rear brake fitting off of the master cylinder and there was always fluid in the MC.

Nothing has changed. They still go right to the floor. So I've narrowed it down to either:

1.) The factory brake proportioning valve
2.) Bad or wrong rear wheel cylinders
3.) Bad master cylinder, even though it is a remanufactured unit with 100 miles.

It does not matter, bleed the wheels R/R/L/F R/F/L/R. You changed master a few times, you may have air in system. I thought you said you bleed entire system in the order i have listed.

 

[SPOT MY 6]

I did before I removed the line lock. I bled the fittings from the farthest to the closest like your supposed to do (RR, LR, RF, LF).

The brakes were soft.

So I just removed the line lock out of the front brake line (didnt even TOUCH the rear brake line) so theres no way the rear line could get air in it.

I re-bled the fronts, and they are still soft.


So what you are telling me is that I should bleed ALL the brakes again, even though I havent touched the rear lines? That doesnt really make sense but Im desperate to have fricking brakes on this piece of frickin you know what.

 

[Red Regal T]

Maybe you're just bleeding your brakes improperly. Just seems peculiar you keep ending up with the same situation. What is your procedure? Are you doing them yourself or with a helper? Just looking for a reason for your problem. I'm usually by myself when I bleed brakes and just run a hose off each wheel bleeder, into a bottle of brake fluid and keep filling the MC. I'm familiar with the concept of the gravity bleed, but I've never actually done it.

 

[turboman38]

I just did this conversion and my original cast iron proportioning valve was leaking so I put a brass one on. I also agree with the bench bleeding. I bought a rebuilt master cylinder from Carquest. The instructions said to bench bleed until there was no more than one quarter inch of travel in the piston.

My vacuum source is teed into the PCV and I had the car out for the first time yesterday. My brakes were stiffer after the conversion so I'm pretty happy so far.

 

[SPOT MY 6]

John, Ive done both the pumping method and gravity.

How I bled the MC:
Had friend pump brakes 4 times and hold on 4th pump. While pedal is pressed, cracked open fittings on MC with a rag wrapped around the fitting to catch the fluid. Tighten the fitting then release brake and repeat procedure. I did this 5 times for both lines comming off the MC.


Pumping:
Have someone pump the brakes 4 times with car off and hold on 4th pump. Crack open RR wheel cylinder while they push brake to floor. Close wheel cylinder bleeder then tell the pumper to release the brake and pump slowly 4 more times and hold on 4th. Repeat 6-10 times per wheel.

Then I go to the LR, then RF, then LF.


Gravity bled:
Filled up MC and cracked open one fitting. Let it slowly drip for 25mins. At this point the MC was only about 1/3 full. I tightened the fitting then moved to a different wheel and repeated.


Does this sound ok?

 

[Black Sabbath]

Here is a suggestion on how to track down the culprit. Clamp off the soft lines going to the calipers and rear drums. Then pump up the brakes. If the pedal still goes to the floor you either have a bad master cylinder or air in the system someplace before the clamps. If the pedal is rock hard have a buddy work his way around the car removing the clamps one by one starting at the rear and working towards the master cylinder. If the pedal goes soft after removing one of the clamps there is your culprit. I hope this helps.

Black Sabbath

 

[wagon]

Sorry but I have to disagree with pinching the brake hoses. The hoses are high pressure lines. If you clamp down on those, you will damage and weaken them. They may not leak, but they can collapse. I had this before, and it caused the caliper to not release all the way, and drag.
I also believe that you probably have air in the lines. If your prop valve is not leaking then I doubt that would be your problem. I also don't think that a Line Lock leaking internal would give you this problem. I had a truck that had no back brakes. I kept bleeding a little out of the rear wheels. Still no brakes. Finally I picked up a quart bottle of fluid, and used almost all of it just bleeding the rears. Great brakes after that. The method that I now use to bleed them, and seems to work great: Remove each bleeder screw, put some grease on the threads, to prevent air from getting sucked back in. Stick a hose on the bleeder, and stick the hose in a glass jar. I prefer Planters. Slowly pump the pedal until you see no more air. Make sure you don't let the MC run dry, or you have to start all over. Make sure the end of the hose stays submerged under the fluid. Good Luck, and let everyone know what you find.

Brian

P.S. Of course these are all just my opinions, and I could be wrong about everything.

 

[BJM]

Make a pressure bleeder. Install an air line into an old MC cover and apply some air. Crack open a bleeder and the liquid will squeeze out.

 

[SPOT MY 6]

Originally posted by turboman38
I just did this conversion and my original cast iron proportioning valve was leaking so I put a brass one on. I also agree with the bench bleeding. I bought a rebuilt master cylinder from Carquest. The instructions said to bench bleed until there was no more than one quarter inch of travel in the piston.

turboman38, how did you bleed the MC? Was it on the car? I think I am going to re-bleed the MC using a different technique rather than cracking the fittings open where the lines connect into it. How did you do it? Thanks a lot man.


Red Regal T,
How did you do it by yourself? Did you attatch a hose to the bleeder and put the other end in brake fluid and just pump? Wouldn't air get sucked in through the threads since the bleeder is loose?


To remind everyone:
In my original post in this thread, I stated that I also took the car to Sears to have them bleed the brakes with their machine to make sure. Even after Sears did it they were soft and just the same as they were when I bled them. I even told the brake techinician to let a LOT of fluid through the lines. He did go through a lot of fluid to make sure. Still the same.

What is the proper way to bench bleed the MC? I have read a few different procedures. The way I did it is a few posts up. I would like to try bleeding the MC again to be 100% sure there is no air in that thing.

 

[Nocooler]

It sounds like your master cylinder is your probelm. It needs to be bleed internally before you hook up the lines to it! All of the master cylinder's I've bought have to rubber hoses and explict directions in the package to do so.

 

[NJTurbo]

Does it go all the way to floor and brake light comes on or is it just soft as this point.

 

[Red Regal T]

I know you recently installed the MC. Did you initially bench bleed the MC? If not, that may be your problem. This is done by placing it in a vice and attaching hoses to the fittings and running the hoses into the MC. Keep them submerged in fluid while you push in the plunger until no air bubbles are in the system.

You're correct on how I do my solo bleeding. I haven't had a problem with it.

I don't want you to think I never had my problems with brake bleeding 'cause I have. Just trying to get you past your problem.

 

[SPOT MY 6]

Nocooler, the MC didnt come with anything except the MC itself and two plugs in the brake line ports.

njturbo, the brake pedal goes all the way to the floor. The brake light does not come on. I no longer have the Powermaster so the wires are all disconnected.

Red Regal T, I am going to pull the MC off and bleed it the correct way in a vise and see what happens. I have a feeling this is the problem...


I will post back after I do this either tonight or tomarrow.

 

[zam70]

You can "bench bleed" (BB) it on the car.
Go get a "bench bleed" kit (should have 2 fittings a length of hose and a little fancy clippy thing that never seems to work)

Undo your lines from the MC, put in the BB fittings, cut the rubber line in half (unless it is already in 2 pieces) push one on to each fitting, run each line to it's corresponing reservoir, pump pump pump away. It's best if one person stands at the MC and holds the lines in because they sometime flip out .
Bench bleeding can sometimes take FOREVER. You can't pump to much so grab a beer and/or a smoke and pump away. Then do it again. Then, in your case, you'll probably have to rebleed the rest of the system as well. I use one of the Vac bleeder pumps. Works great and fast.

 

[SPOT MY 6]

Originally posted by zam70
You can "bench bleed" (BB) it on the car.
Go get a "bench bleed" kit (should have 2 fittings a length of hose and a little fancy clippy thing that never seems to work)

Undo your lines from the MC, put in the BB fittings, cut the rubber line in half (unless it is already in 2 pieces) push one on to each fitting, run each line to it's corresponing reservoir, pump pump pump away. It's best if one person stands at the MC and holds the lines in because they sometime flip out

When the pedal goes to the floor, does that mean that the piston on the MC is all the way in, or is there something else that stops the pedal (and the piston still has more travel)?

Would I be able to get more travel out of the piston on the MC if it was out of the car? I assume the pistons needs to go ALL the way in the MC in order to get all the air out?