Hard Brakes = Brake Booster?

[homerj1]

My newly acquired 94 Jetta has a hard brake pedal when brakes are applied.

When I start the car, with my foot on the brake pedal, the pedal drops a bit.
But still feels pretty hard compared to my 95 Jetta.

There seems to be lots of vacuum when the engine is running ( I pulled off the vac. line at the booster and covered the end with my fingers)

Where do I look next?

Could this be a vac. line check valve issue, or is my booster cooked?

Aivars

[jtanguay]

does the car stop good?  if the car stops good then maybe your brakes have been looked after properly...  mushy brakes aren't good!

[homerj1]

The hard pedal effort makes it difficult to stop the car.
No mushiness - instead you have to press really hard on the pedal. Even then the wheels won't lock up.

[jtanguay]

The hard pedal effort makes it difficult to stop the car.
No mushiness - instead you have to press really hard on the pedal. Even then the wheels won't lock up.

hmmm you might get lucky and the brakes just might need bleeding, but from what you describe it is either someone installed a much bigger master cylinder, or the brake booster is toast

if you have a vac gauge lying around you could measure  your system just to rule out the vac pump.

[BellCityDubber]

The hard pedal effort makes it difficult to stop the car.
No mushiness - instead you have to press really hard on the pedal. Even then the wheels won't lock up.

hmmm you might get lucky and the brakes just might need bleeding, but from what you describe it is either someone installed a much bigger master cylinder, or the brake booster is toast

if you have a vac gauge lying around you could measure  your system just to rule out the vac pump.

In my case last year, I've replaced just about everything on the braking system.

I had magical "disappearing" fluid.... no visible leak, and had a high and hard pedal... and while driving the car would start to apply the brakes "on it's own" without pushing the pedal, and the pedal felt hard, and was high and hard.


What it turned out to be was:  The Master cyl caused a leak from out the back of the seals and leaked into the booster.  There was about a litre of brake fluid in my booster.  When I cleaned out the fluid, the diaphram in the booster had been eaten away by the brake fluid and the vacuum side and the neutral pressure side of the booster were comprimised.

After running the car (generating vacuum) the front (vac) portion of the booster held vacuum until the diaphram gave out and leaked vacuum into the neutral side (back side.. towards the cabin) of the booster.... causing the brakes to "self apply) because the pressures weren't correct, the pedal felt hard and because of that, the diaphram would begin to automatically apply the brakes...


so you may want to check your booster, or pull one from a wreckers and change it... it's only 4 13mm nuts that are easily accessable from inside the car/under the dash/drivers footwell...


HTH

[homerj1]

Thanks for all the great insights!

2 more questions -

1. What should the vacuum reading be?

2. Bentley suggests that I need a "special tool" to disengage the brake booster rod from the brake pedal assembly ( this is a  Mk3 Jetta). How "special" is this tool - or is there an easy way to do this?

thanks

Aivars

[bigblockchev]

Hard brakes is most likely a leaking diaphragm in the vacuum pump or a crack in the fitting at the top of the vacuum pump. this is what I have found in any case. The diaphragm is a $14 item and not too hard to change. cheers Dan

[burn_your_money]

Check to see if your pads are fully contacting the rotors, if they aren't it will seem like the pedal is hard in order to stop because you are basically running smaller rotors.

Your description of the pedal sounds normal to me

[homerj1]

The Jetta has sat for a few days as I was replacing the rear control arm bushings - but that's another saga....

When I started up the car there was a few brake applications where I had power assist. So I guess it is either vacuum pump or brake booster.

The check valve seems ok - so I am going to change out the vacuum pump( the easiest one first?) - although  my Bentley manual doesn't seem to refer to it.

Are there any tricks to replacing the vac. pump - is it a straight unbolt and bolt?

Thanks

Aivars

[Vincent Waldon]

It will unbolt and pull right out... consider replacing the green o-ring 'cause it will likely not have been moved for many years and will suddenly start to leak now that you've disturbed it.

[homerj1]

Thanks Vince!

I replaced both the vacuum pump, line and check valve. No change.

I then took apart both and cleaned both front brakes. Calipers move ok.

Finally removed the brake booster from my parts Golf. So tomorrow, I'll install that into the Jetta as a last resort.

 Although,  with visions of broken rusty bleeder screws running through my head....

Aivars

[homerj1]

Just an update on my 95 Jetta. The booster was the problem, so now the brakes work great.

A few tips that I found worked.

1. I didn't use the VW special tool to remove the booster pushrod from the pedal assembly. I just gave the brake pedal and quick snap backwards and the pushrod ball end just popped out. (Got this from the Vortex forum - but there were cautions about breaking a plastic piece in the pedal assembly) I did however, bend the bracket that holds the brake light switch - so I had to bend it back.

2. I was able to remove the booster without having to loosen or remove the brake lines running to the brake master cyl. I basically moved the master and carefully bent the brake lines to the right (driver's side and downward). I was able to move the booster forward & up.

I hope this might help someone.

Aivars

[Quantum TD]

Yeah. The mysterious "brake leak" told me it was the booster. Wish I saw this thread earlier. I could have told you to go straight to that. Anyway, glad to hear you fixed your problem.