"Pumping the Brakes" restores harder pedal

[RWebb]

If I have a soft brake pedal and "pump the brakes" to bring it back, does that mean the power brake booster has a leak?

Or could it be something else?

I ask because it has been a long time since I drove anything that was either so new there were never brake problems, or so old it never had power brakes in the first place...

and, yes, it is the Vanagon...

[Shifter]

If your booster was leaking, you would have a hard pedal. If you have to pump, I would guess a failing master cylinder.

[john walker's workshop]

air in the lines/ drum brake shoes too far from the drum/ front disc wobbly due to bearings needing adjustment..........

[Zeke]

Hey, JW, does the dual circuit master cylinder as used on the early 911 do something similar when it goes to the secondary circuit? Or before it gets down that far?

I'm not sure I know how to ask the question.

[RWebb]

thanks - probably drum brake shoes too far from the drum

I had a VW shop redo the rear wheel bearings and they did not adjust the rear drums correctly

the Vanagon has an auto adjuster so it should come back into position soon

[on2wheels52]

Something needs fixing, at least as far as my mid '80's auto mechanic days remember.
And re "so old it never had power brakes in the first place..." just how old a
guy are you? The first two 'family' cars I experienced had manual brakes.
Zeke may be a bit older than me.
Jim

[DanielDudley]

Originally Posted by RWebb

thanks - probably drum brake shoes too far from the drum

I had a VW shop redo the rear wheel bearings and they did not adjust the rear drums correctly

the Vanagon has an auto adjuster so it should come back into position soon

IIRC, there is an oval access port on the bottom of the back plate with a rubber plug. Popping that off gives you access to a star adjuster wheel that screws out to tighten the shoes.

[A930Rocket]

Do the brakes pulse? Rotors might be just warped enough to push the caliper pistons in a touch.

[vash]

why are we thinking this is something more than simply air in the system? i think it just needs to be bled..big time.

if you can pump it up and get the stiff feel..the system for the most part is working, right? if the pedal gets stiff..and phsssh! it slowly creeps to the floor, something is wrong. MC bad, or booster crapped out..

[Tobra]

Air in lines or MC going. Rear drums out of adjust will not give soft pedal. Bleed the brakes, if problem persists, MC replacement.

[speeder]

The correct answer is that you check everything, from the wheels inward to the pedal. In that direction and order. When it comes to brakes, I don't fk around and guess.

[RWebb]

thx - they do have a star wheel in there - looks like you have to take the wheel off to get at it.

possibly the m/c -- it is 1.5 years old (!) and I bought it from the most expensive and largest Vanagon parts supplier to ensure it was a quality part (the VW new parts scene seems to be heavily infested with low quality parts made out of chinese drywall) -- so get this, I looked at the m/c ~6 months after I installed it (and it goes into the passenger cabin BTW) and the outside of it was totally rusted over - they had used some sort of super cheap paint or coating on it.

The system has not been opened up recently, so I don't think it has air in it (except maybe from a possibly bad m/c).

No pulsing - the front rotors and rear shoes are 1 year old and have < 1,000 miles on them.

All wheel bearings are new - of course, with the shops here not exactly inspiring confidence maybe they effed them up...

I'll drive it around for awhile and see if it gets better.

[RWebb]

Originally Posted by vash

if you can pump it up and get the stiff feel..the system for the most part is working, right?

if the pedal gets stiff..and phsssh! it slowly creeps to the floor, something is wrong. MC bad, or booster crapped out..

yes, it's working for the most part

Is the test above done with the motor running (power booster) or motor off?

I think I recall some test like that done with motor running, then with motor off to determine if the problem is in the m/c vs. a leak in the power booster...

[crustychief]

It is probably a good time to get a jug of brake fluid and replace the fluid that is in there since it is almost 2 years old. You will bleed the lines in the process and eliminate air in the lines as a possibility.
P.S. I think it may be air in the lines.

[vash]

i am far from being a brake expert. but i seem to remember being told that the booster does nothing but take some of the effort from you.

so.. if you pump them up firm with the motor running, it will be the same thing with the motor off..except you will be pumping them up firm-er..or it will take more effort to pump them up firm.

i bet you a VOODOO donut that it is simply air in the system.

[Tervuren]

Originally Posted by vash

why are we thinking this is something more than simply air in the system? i think it just needs to be bled..big time.

if you can pump it up and get the stiff feel..the system for the most part is working, right? if the pedal gets stiff..and phsssh! it slowly creeps to the floor, something is wrong. MC bad, or booster crapped out..

Bleed it, it works right, and in a few days you have problems again, then its more than air in system. And if it failed in an even bigger way, and that is how you found out, you'd wished you'd looked over it.

My '86 944 had similar systems when I picked it up from a shop, they said nothing wrong with the brakes when I brought it back(along with a few other issues that they didn't do right the first time).

Turns out I had a crack in my master cylinder at the Base!!! Brake fluid out when I pressed the pedal. Pumping the brakes would get there, but I stopped driving the car until I got a new master cylinder.

[scottmandue]

Pumping the Brakes, restores harder pedal.

So that is what the kids are calling it nowadays

[beepbeep]

Start the engine and hold the foot firmly on brake pedal. If it slowly sinks, you have failing MBC gasket. If not, check for air bubbles or excessive pad play.

P.S.
You might want to fix this quickly.

[RWebb]

mbc?