'89 b2 brake problem

[greyghost]

Like the previous "saggy brake" post, I have about the same problem with my '89 except the pedal to floor issue is intermittent. Roughly every five or ten times I use the brake the pedal goes to the floor.

This morning I got in the truck and put my foot on the pedal without the engine running and the pedal wouldn't move (as expected). As soon as the engine starts the pedal goes to the floor with little or no resistance. After that it worked fine.

fluid level on the mark
no leaks
vac lines look good
complete front and rear brake job about 17,000 miles ago with RABS valve replaced and system flushed

Any help on this would be greatly appreciated!

Ken

 

[bd2988]

Look at the brake booster check valve and the grommet. I had the same problem with the brakes intermittently going to the floor. The grommet around the valve was cracked. I replaced it and now my brakes work fine. The part I bought was Raybestos CV89000 on Rockauto.

 

[greyghost]

I replaced the check valve and grommet. Still have the problem. Will keep looking.

Ken

 

[bd2988]

Sorry to hear that didn't work for you.. I had the same exact problem but that solved it for me. It was worth a shot though.... Perhaps it is actually something with your brake booster itself.

 

[greyghost]

Can't figure this out. If the brake pedal goes all the way to the floor wouldn't that mean the pistons in the master cylinder are moving far enough to activate the brake warning light? If you loose vacuum the pedal will be harder to depress, but you should still have brakes.
Seems like an internal hydralic leak in the master cylinder. But then in the "saggy brakes" post the OP says he replaced the master cylinder and it didn't help.

Ken

 

[greyghost]

Well I finally got around to having this checked out.
Replaced the master cylinder and the brakes work fine.
Just thought I would let you know what finally fixed it.

Ken