Brake Troubleshooting, PMB all around Options

[OU8AVW]

So I'm getting to bleeding my brakes. I have replaced every item with parts from PMB. That's all the hard lines, soft lines and all calipers and pads. The installation was pretty easy but I'm not beyond making mistakes. The stuff has been sitting a while, installed with no fluid in the system.

Please note that I've done this on quite a few VWs so bleeding brakes is not foreign to me. I just did this exact process on my '89 Westy with good results.
(IMG:style_emoticons/default/sheeplove.gif)
I can get a steady stream of fluid through all bleeders both with a vacuum pump and also with pedal action
I see no signs of leaks
I get no pedal and it seams that the pedal won't actuate any of the calipers (More on this) with normal action.
This morning I went though all the calipers and moved a considerable amount of fluid though them by pumping the pedal with similar results until....
I pumped the brakes a bunch and finally got action on the front brakes but then they were stuck. No action on the rears.

I did not bench bleed the master. I did crack the hoses on the master until I got fluid from each of them.
I have speed bleeders installed, so far I am not a fan.

What could I have messed up in the install?
Why are these things sticking?
Next step?
Thanks.....

[Dave_Darling]

Have you bled the prop valve on the firewall?

Not sure about the sticking.

--DD

[Mblizzard]

You would be amazed at how air can hide in a system. It takes such a small amount of air in a system to render it useless. Doing a complete rebuild can put a lot of air in the system. For me, nothing gives you the feedback needed like attaching a clear hose to the bleeder screw and then submerging it in a clear container of brake fluid. Sometimes a zip tie is needed at the bleeder but you will be able to see even very small air bubbles as the come out. I know you did vacuum but this is worth a try before tearing everything out.

If you do this and get no air at all 4 calipers and all bleeders (both on the rears) then you have to think MC.

[ClayPerrine]

It is possible to turn a cup on the master cylinder if you go to full stroke when dry. Once that happens, you will never get brakes on the car.

And I second Damp Dave's suggestion. Bleed the proportioning valve on the firewall. If it has air, the back brakes will never work.

Also, check the venting clearance on the rears. Too much clearance will result in huge pedal travel.

[Johny Blackstain]

Curious, how does one bleed the proportioning valve? Also, how does it fit in the bleed schedule (farthest to nearest)?

[Bartlett 914]

I like to use clear hose at the bleeders. I run the hose up vertically. This leaves fluid in the hose down to the bleeder. It makes it easier to see bubbles and less of a chance air can get back in the system. Also I press the pedal quickly. This moves the fluid faster. On the rears in particular, there is a hoop in the line where air can get trapped. Pressing the pedal quickly (smartly as Haynes puts it) helps push any air out and around the bend.

[OU8AVW]

Awesome, new things to try. I assume bleeding the proportioning valve involves cracking the highest fitting?

[earossi]

I just went through this on my car. We pushed over two pints of fluid through the system using a pressure bleeder. The MC was bench bled before installation.

In the end, I focused on two areas: the proportioning valve and the master cylinder.

Since I had fitted staggered wheels on my car (8 rears and 7 fronts), I was not concerned about locking up the rears, so saw little value in retaining the proportioning valve. I replaced it with a Tee fitting that a number of folks have used for that purpose.

That did not fix my issue. I could push on the brake pedal and watch it go to the floor. So, that left only the master. Even though we had bench bled the assembly, I decided to slack off on the outlet line nuts as had been recommended on this sight. I backed both nuts off just enough so that I could see a slow seep of brake fluid at each nut. We left the car to gravity bleed in this fashion for a couple of hours. Once done, we tightened the outlet nuts and topped off the reservoir.

We had a hard pedal! Never seen this phenomena before on any of my other cars, but apparently there is an area within the MC configuration where some air can reside despite normal bleeding procedures.

So, give it a try. You did mention in your narrative that you had bled the MC at the outlet ports........but, did you allow it to slow bleed for a couple of hours?

[OU8AVW]

I just went through this on my car. We pushed over two pints of fluid through the system using a pressure bleeder. The MC was bench bled before installation.

In the end, I focused on two areas: the proportioning valve and the master cylinder.

Since I had fitted staggered wheels on my car (8 rears and 7 fronts), I was not concerned about locking up the rears, so saw little value in retaining the proportioning valve. I replaced it with a Tee fitting that a number of folks have used for that purpose.

That did not fix my issue. I could push on the brake pedal and watch it go to the floor. So, that left only the master. Even though we had bench bled the assembly, I decided to slack off on the outlet line nuts as had been recommended on this sight. I backed both nuts off just enough so that I could see a slow seep of brake fluid at each nut. We left the car to gravity bleed in this fashion for a couple of hours. Once done, we tightened the outlet nuts and topped off the reservoir.

We had a hard pedal! Never seen this phenomena before on any of my other cars, but apparently there is an area within the MC configuration where some air can reside despite normal bleeding procedures.

So, give it a try. You did mention in your narrative that you had bled the MC at the outlet ports........but, did you allow it to slow bleed for a couple of hours?

I'll try this for sure. Thanks for the good input. (IMG:style_emoticons/default/biggrin.gif)

[ChrisFoley]

Curious, how does one bleed the proportioning valve? Also, how does it fit in the bleed schedule (farthest to nearest)?

There is zero need to bleed the proportioning valve separately from the rear calipers.
Anyone who tells you otherwise is simply perpetuating an old wives tale.
The exit side of the valve is at the top, therefore any air (a tiny volume actually) in the valve body will leave as soon as fluid moves toward a rear caliper.
That's my humble opinion. (IMG:style_emoticons/default/shades.gif)

The bleeding method we follow in my shop requires someone in the car to pump the pedal and someone under the car to open the valves one at a time.
We pump the pedal several times to compress the air bubbles, before opening a valve - with pressure on the pedal to move the fluid.
The pedal is held down until the bleed valve has been re-closed - repeat the procedure until no air comes out with the fluid.

I've never had good luck with speed bleeders on a dry system and I've never had good luck with a vacuum bleeder.

[Peashooter]

Did you replace the master cylinder with a fresh new one? I went through the brakes on a friends car a while back, and installed a new m/c he had in stock on the car as a part of the process. We could get fluid every where easily, but not a good pedal. Finally took apart the m/c and one of the cups had cracked. Turns out it was a new m/c, but had been lying around for years. A fresh m/c and all was well. Do bleed the proportioning valve as well, as noted. Just crack the fittings around it while having pressure on the pedal. Makes a difference usually.
Good Luck!

[76-914]

Curious, how does one bleed the proportioning valve? Also, how does it fit in the bleed schedule (farthest to nearest)?

There is zero need to bleed the proportioning valve separately from the rear calipers.
Anyone who tells you otherwise is simply perpetuating an old wives tale.
The exit side of the valve is at the top, therefore any air (a tiny volume actually) in the valve body will leave as soon as fluid moves toward a rear caliper.
That's my humble opinion. (IMG:style_emoticons/default/shades.gif)

The bleeding method we follow in my shop requires someone in the car to pump the pedal and someone under the car to open the valves one at a time.
We pump the pedal several times to compress the air bubbles, before opening a valve - with pressure on the pedal to move the fluid.
The pedal is held down until the bleed valve has been re-closed - repeat the procedure until no air comes out with the fluid.

I've never had good luck with speed bleeders on a dry system and I've never had good luck with a vacuum bleeder.

(IMG:style_emoticons/default/agree.gif) This works for me as well. I have a mighty vac but it doesn't move the fluid quiet as quickly as having someones big foot on the pedal. Eric has an easy method on his site as well. I might try it the next time. Looks and appears logical. Also, search for McMarks "long tube" method. Same process as Chris mentioned but for a one man show. (IMG:style_emoticons/default/beerchug.gif)

[Dave_Darling]

Another recent brake thread just reminded me:

Are the bleeders on top of the calipers? If they're not, you will never ever ever get a good pedal, no matter how much you bleed. We've had people try to use the bottom bleeder on calipers that had two, and we've had people swap calipers left for right, giving them only a bleeder on the bottom. The air never comes out that way.

--DD

[OU8AVW]

Another recent brake thread just reminded me:

Are the bleeders on top of the calipers? If they're not, you will never ever ever get a good pedal, no matter how much you bleed. We've had people try to use the bottom bleeder on calipers that had two, and we've had people swap calipers left for right, giving them only a bleeder on the bottom. The air never comes out that way.

--DD

They are on the bottom. So I need to swap left for right? Does that work with the hoses?

[mepstein]

Another recent brake thread just reminded me:

Are the bleeders on top of the calipers? If they're not, you will never ever ever get a good pedal, no matter how much you bleed. We've had people try to use the bottom bleeder on calipers that had two, and we've had people swap calipers left for right, giving them only a bleeder on the bottom. The air never comes out that way.

--DD

They are on the bottom. So I need to swap left for right? Does that work with the hoses?

Yes

[Eric_Shea]

Another recent brake thread just reminded me:

Are the bleeders on top of the calipers? If they're not, you will never ever ever get a good pedal, no matter how much you bleed. We've had people try to use the bottom bleeder on calipers that had two, and we've had people swap calipers left for right, giving them only a bleeder on the bottom. The air never comes out that way.

--DD

They are on the bottom. So I need to swap left for right? Does that work with the hoses?

Bleeders (air) always go to the top. Calipers are full of air. Bingo.

And... 914's do not come with proportioning valves. It's a rear anti-lock brake device. Why would ya need one of those? (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/wink.gif)

[OU8AVW]

Ok, I ditched the speed bleeders and swapped the front calipers, rears were correct. I'll try bleeding it tonight and report back.

[OU8AVW]

Ok, much better result last night. Using the vacume bleeder I have brake action but still a pretty soft pedal. I'll do the foot method next.
Thanks for the help. Dave nailed it. I knew I had a simple mistake.