Hi guys. I recently did some brake work with my friend who is a VW master tech. We swapped a couple of hubs and did the brake rotors, pads, ss lines, and flush. Of course, we bled the lines (five times) and had great pedal feel. I have to say that the braking had been greatly improved to the point that I had confidence in braking for the first time. After a few weeks I noticed that I would slowly start creeping forward at a stop light. It seems that intermittently my brake pedal will slowly start loosing pressure and creep toward the floorboard (and if my foot doesn't follow, I'll start rolling ever so slowly). It's not every time. It seems to happen about 20% of the time that I'm at a stop. I can't seem to find common theme other than it seems to happen more after I've been driving for a while. Thank you guys for any advice.

 

The pedal does sink very very slowly with the engine running on tickover it's a function of the servo but it wil stop very rapidly when the pedal is hit under way and the TC and ABS will work OK. With the engine off the pedal should pump up rock solid once the servo vacuum is exhausted. It sounds like you may have master cylinder issues or maybe servo issues, it's hard to say. It can often develop issues after the system has been flushed through and bled particularly with older master cylinder rubbers that have been installed for a long time. Sorry, can't really think of much else that would cause the same problems.

 

Thank you, I noticed that when the truck sits outside, the braking is amazing when it's freshly started and cold. After a while, the pedal starts to sink. I did confirm that the pedal pumps up and is rock solid when the vehicle is off. Is there any way to check the servo or master cylinder without swapping them out? I think I might also replace the manifold brake booster line and that manifold connector. Mine is intact, but could probably use refreshing. Thanks again for any input.

 

I'm experiencing the same issue as you. Except that I have to pump the pedal twice in order to stop in time. I'm heading to Harbor Freight tomorrow to pick up a vacuum bleeder. If the bleeder does not correct my issues, My next move is to replace the Master cylinder.

 

Try bleeding by using the ABS modulator to do the work for you. I had to replace my master cylinder reservoir last weekend, and rememered seeing something about jumping a relay to bleed the brakes on an Australian LR forum.
I got my standard clear hose coming off the bleeder into a clear bottle. Next I removed the ABS relay from the underhood relay panel and jumped it with two wires. This activated the modulator (same sound as when HDC is used). I then loosened the bleeder and watched the clear jar fill with brake fluid rather quickly. Once the air bubbles stopped and only fluid was entering the jar, I tightened the bleeder and un-jumped the relay. I used the RAVE sequence for the bleed: RF, LF, RR, LR and my pedal has never felt better.

 

It sounds like the master cylinder. If the pedal sinks it is because fluid is moving past a seal somewhere. If it isn't leaking out of a caliper then it must be leaking past the seals at the other end of the system. That type of leak won't let air into the system so your braking may feel great at times also.

 

I picked up the cheaper Harbor Freight Vacuum Bleeder Kit this morning and went to town on bleeding. Looked at RAVE for the procedure, scratched my head, went to the forums for a refresher and ultimately decided against following the procedure described in the RAVE.

I started at the PS rear caliper, then hit the DS Rear caliper then, PS Front then, DS front.

I pulled air out of the rear two calipers by the time I reached the fronts all air seemed to be expelled from the system. I was surprised to see that much air purge out. But that seemed to restore pedal feel and stopping power has been greatly improved.

 

I'm thinking that it's my master cylinder. My logic is that when the brake fluid is cold ant thick, it doesn't readily pass by the seals. When it heats up and becomes less viscous, it passes by the seals and creates my pedal issue. Thanks guys, looks like a master cylinder is in my future soon.

 

What is the number of the relay you jumped? This sounds like a dream come true.

 

Relay #10 in the underhood fuse/relay panel and I jumped terminals 3 and 5. If you look at the side of the relay there is a diagram, and the terminals are numbered.