brake booster??

[davidpa28140]

Hello, I have a problem with my brakes(again) on my 83 rabbit pickup. About two months ago I replaced the master cylinder, both rear drums, both rear wheel cylinders, one of the front calipers and all shoes/pads. Brakes worked great for a month and really, still do but.... after pressing the brake pedal, the pedal stays down and the brakes remain on until I do one of the following; pull the pedal up with my foot or drive a bit down the road.

I have bleed the brakes twice after this started and have been watching the fluid level. I have lost no fluid and got no air from lines.. Today I took the rear drums off, in hopes the shoes were not being retracted by possibly weak springs, but that is not the case.

The engine and vacuum pump are from a tdi, the booster/MC are factory rabbit pickup stuff. I have read a few post of guys testing vacuum from the vacuum pump, but have not tried this yet. Are there possibly any check valves in this system?

Anyone have any experience with this??

As always thank you, Dave

[caveman]

Try this: disconnect the vacuum line from the booster, pump the brakes a few times to release the pressure and then try it. The other possibility is that the adjustment at the booster rod is wrong. Not to sure it would cause your problem, but should be checked anyways.

[davidpa28140]

OK, pulled the Vacuum line out of booster, pushed on brakes several times, they remained firm and the pedal did not "stick down" as before or go as far down.

After this exercise I started truck and stuck my thumb over vac hose, seems like lots of vacuum. I stuck the vacuum hose back in booster, brakes effective, but soft and pedal wants to stay down until lifted up just like before..

[vanbcguy]

I've had a bad booster do exactly that before. There's a valve in the booster that's activated when you push/release the pedal, once they go bad you either get no assist or it sticks on like you're describing.

No idea if it can be fixed - when mine went I happened to have another car around with a compatible-enough booster. Swapped it and it was all good. Boosters are totally junkyard-compatible - they don't fail all that often and they're rarely pulled.

[Quantum TD]

Been seeing alot of bad boosters lately. They're becoming a popular item for MK1 Rabbits and Pickups. The German-made Jettas, Cabriolets, and Sciroccos all use ATE boosters, which are essentially the same thing used on all VWs after 1985. But the Rabbit ones are specific to those models. I just sold my last good one. I've sold/replaced about 1/2 dozen in the past year.

[davidpa28140]

Thanks for the insight guys, always a lot of great knowledge found here. I think I will start shopping for a booster.

Thanks again,
Dave

[Vincent Waldon]

the Rabbit ones are specific to those models. I just sold my last good one. I've sold/replaced about 1/2 dozen in the past year.

ETKA doesn't list a part number for the Pickup brake booster unfortunately... do you know what it is? Might have to stock up myself.

[davidpa28140]

Hi Vince, I found them at several places in the US, autozone and advanced auto to name two. Priced at 90 to $100.

[davidpa28140]

Replaced brake booster today, it came with a new check valve. Still have the pedal sticking down problem...... only difference now is when the brakes come on they are rather strong and when the pedal sticks down it holds the truck tight to the point that it may stall if I tried to pull out.

Brakes seem to be weak until about mid pedal stroke then they come on very strong. I did get some air out of the bleeders which seemed to help a little. I think the air may have gotten in there when I had to take the brake master off to get the booster out.

I saw a mention of an adjusting rod in there, I think it is between the booster and the MC , I have replaced many MC before and have never done anything to this rod. Could this be my grief with this one??

I also pulled the vacuum of of the booster and drove the truck, the pedal did not stick down????

Any idea's???

[hagar]

The adjustment of ROD is CRITICAL . and easy to do. It has a spring clip at pedal ..

hagar.

[82vdub]

Just wondering if you have a bad master cylinder. If the piston is somewhat loose in it's cylinder, it could get cocked and stuck and not return. If the pedal stays towards the floor and you can easily pick it up and there's no resistance, then that would say the issue is outside of the pivoting mechanism for the brake pedal. If the brake pedal stays down and the brakes release when the pedal is pulled up, then it may be a sticking pivot for the brake pedal. Have you checked for this?

EDIT

Now that I re-read your initial comments, if the brakes release when the pedal is pulled up, inspect the brake/clutch pedal assembly inside the cab for points where it could stick, or bad bushings etc.

[hagar]

It is many years since I did one BUT it sounds to me the rod is too long there must be play with no foot on pedal Remember there is a valve system involved , to remove the vacuum when pedal is at rest.

Try shortenng it by say 3 turns it is a turnbuucle type of adjustment AND it is tricky and critical. but fast and simple job.

hagar.

[Op-Ivy]

I had the exact same problem as well a few years back. But it turned out to be my brake booster as well. Good luck!

[davidpa28140]

I haven't seen any adjustment on the inside of the cab. When I did the tdi swap I had to greatly modify the pedals, the cable clutch conversion for the 02A transmission has far greater resistance than the original 020 transmission did, I say all that to get to the point anyway, I think my problem with the pedal sticking down maybe with the shaft that runs thru the brake and clutch pedal. I pulled the shaft nearly out and lubed it. The pedal is no longer sticking, although if there is a bushing behind the clutch pedal I will be replacing it next........it's getting really wobbly.

Thanks for all the good advice guys! Your tops

[hagar]

davidpa28140
said : Hello, I have a problem with my brakes(again) on my 83 rabbit pickup. About two months ago I replaced the master cylinder, both rear drums, both rear wheel cylinders, one of the front calipers and all shoes/pads. Brakes worked great for a month and really, still do but.... after pressing the brake pedal, the pedal stays down and the brakes remain on until I do one of the following; pull the pedal up with my foot or drive a bit down the road.

I have bleed the brakes twice after this started and have been watching the fluid level. I have lost no fluid and got no air from lines.. Today I took the rear drums off, in hopes the shoes were not being retracted by possibly weak springs, but that is not the case.

The engine and vacuum pump are from a tdi, the booster/MC are factory rabbit pickup stuff. I have read a few post of guys testing vacuum from the vacuum pump, but have not tried this yet. Are there possibly any check valves in this system?

Anyone have any experience with this??

As always thank you, Dave


Above is what I was trying to answer. and yes hagar has lots of experience , BUT then you said you had modified the brake pedal , hagar does an excit stage left..

However there are a lot of lurkers following this SO ? here is a bit of general VW Rabbit brake system. information.

First what is more important than brakes ? so first thing to do is buy two books. The Bentley and the Haynes .

For real knobs the Haynes is best.. .I call the LDA and ADA and vacuum pump (disgfragm) type) and the Booster.

Air pressure servos. or vacuum servos. After you red the books you are welcome to ask me specific questions .. How to adjust rod from pedal to servo , I use play MINUTE..

I had 3 complete brake failures in my life , 3/4 ton Landrover , Honda Prelude and a 1957 MGA..

hagar.

PS : The brakes MUST work.