Losing brake pressure at stops

[mikracer]

Originally Posted by TheLetterJ

So what's the word? Problem solved, or waste of time?

When braking to come to a stop, the pedal feels good, but at the stop, its still losing pressure. Been at the inlaws since I left your house, so I havent had time to look up other possible culprits.

For everyone else, I went to Jay's house this morning to replace the master cylinder. Jay did most of the work, but we got it switched out and the pedal was still going to the floor with constant pressure at a stop. I bought a new Duralast master cylinder from Autozone (they were the only store that had it in stock) and we bench bled the master. Could the new master cylinder be a defective unit? We didn't see any leaks from any of the calipers and we bled the lines the "traditional" way of furthest from the master to the closest. Any ideas???

[BajaSportsmobile]

PITA!

Start by re-bleeding the brakes after you have driven it for a few days to see if there is a small amount of air left in the system.

Next suspect is the ABS system.

[mikracer]

Originally Posted by BajaSportsmobile

PITA!

Start by re-bleeding the brakes after you have driven it for a few days to see if there is a small amount of air left in the system.

Next suspect is the ABS system.

Does the ABS system need to be bled a certain way?

[mikracer]

Finally got to the bottom of this issue and wanted to post a follow up incase anyone else goes through the same thing. The dump valves on the hydraulic control unit (HCU) for the ABS has failed.

Theres a test you can do to check if the HCU is bad. There are two rubber plugs on the unit that you remove. You then stick a nail or straightened out paper clip into the slots. With the van running, you press the brake pedal and if you see one of them move out more than a half inch, the dump valve has failed. If the dump valves are good, they don't move at all. The rear valve on mine failed so I need to replace it. Unfortunately, they aren't cheap ($800-$900). I guess more money goes into the van...

[JWA]

Wow that's a bummer----sorry to hear about this development. Hopefully that's the last of maintenance expenses for a while now.

Great diagnostic procedure for the ABS unit---I'd never come across that step before. A depost in the Karma Bank for you!

[86Scotty]

Yep, good info. Thanks for sharing.