Basically, its either the brakes or the engine stalled at low
speeds. It has only happened 3 times but when it happened, i
lost total power to the brakes. I couldnt depress the brakes to
stop at the lights! =( i had to reach for my handbrake. becos it
doesnt happen all the time, im caught off guard all the time! worse!
and no mechanic could reproduce the problem so they do not know how to fix it !
is it the engine? the vacuum hose? (i replaced the vacuum hose before) or the brakes ?!

 

Your description is odd, the engine is stalling and your brakes fail?

What is happening, your engine stalls...you lose your brakes....?
Be a little more detailed. VW's are notorious for stalling with vaccum
leaks. I just finished replacing almost all the lines and still have one
left.

 

while wat happened was that after i exited from the highway, i had to slow down for a light. i lower the gear to 4 then to 3. then i tried to depress the brakes BUT they couldnt be depressed! its was probably 20+ mph so i grab my handbrake straight away.

1 thing that im not sure is if the engine died or the brakes caused the engine to stall cos after i stopped, the engine is died. basically, the feeling is that there is no power assist (no vacuum) to the brakes which is the same thing when before u start the car.(u cant depress the brakes)

no idea what happened to cause that problem. i replaced vacuum hose b4 as it was found to be leaking. but problem still persists

 

Seems to have a problem with your vacuum booster. There is a check valve located on the vacuum booster right where the vacuum hose enters the booster. If you have a leak or the engine stalls, this is suppose to give you application of the brakes in the event of your car shutting off or vacuum leaks. The valve should only allow air to be sucked out, (one-way valve) If you are getting air into the booster, then it's not working properly and you could lose your braking system. The booster is essential cause without it, you can't engae the master cylinder. If it's not working right than you have a problem. If you have replaced all your vacuum lines and what not and you are still having this problem, you might want to have your mechanic or someone look at the booster, or just replace it period.
I only say this because even if you engine stalls, as I stated earlier, this booster provides a back up for when you lose engine vacuum so you can still apply the brakes. (The booster works by using the low pressure (vacuum) within the booster and the atmospheric pressure (high pressure) outside to help engage the brakes by pushing a sealed diaphragm which separates the low and high pressure and drives a rod into the master cylinder. If your having a leak, you lose the low pressure within the booster and the booster doesn't work properly or not at all.)

Another idea...

Since it seems to only happen once and a while, you could be getting a wobble down in the caliper. It's self adjusting and if you get a wobble it'll push the pads away from the rotor, resulting in the driver having to pump the brakes a few times to push more fluid into the system and engage the brakes. Go for a drive and see if you can create the same circumstances and try pumping the brake and if after pumping the brakes do engage, you have a wobble, something is pushing the pads( & caliper piston) open. If not, refer to the above and have the booster replaced if you can't find no other reasonable explanation for losing your brakes.

As far as your engine stalling, obviously it's manual, so I don't see how you'd be stalling it since you know how to drive a manual, yes vacuum leaks can cause the engine to stall if it's really really bad and you got the rpm up high and let off the throttle quickly...just to be safe, replace all your vacuum lines in your car, ALL of them, that haven't been replaced yet. It's cheap to replace them if you find some joe-blow shop that sells VW parts. The dealer will be expensive, but if you look, you can find good deals in your local area.

Keep us posted...

-Jeff

 

ok. thanks aLOT Jeff. im going to try out the brakes at a safe location. will keep posted.

 

oh by the way...even if you do "think" you lost your brakes,
you never do, it's just not power assisted. I don't know how
strong your legs are but the brakes always work unless you've
lost a brake line or something. Just takes one heck of a push
to make them work, try turning off your car in neutral, in a
safe location and seeing how much force you need to apply
but they will work if your lines and what not are working.

 

my friend just pointed out that if my car is a manual car and that the gear is in (clutch out) thus if the engine stalled, the car shld stop as a result ? so does that mean that the engine only died after i come to a halt ? Im still trying to replicate the exact problem

 

If the car is on and you have it in gear and let the clutch out the car will hop and stall. In neutral it won't stop the engine. Maybe you stalled it without realizing it.

Aside from that, the braking system is very touchy. Either it works or it doesn't, or it kinda works but is usually constant in its operation. It's rare that a braking system will work perfectly most of the time then occasionally stop working at all. In that case, it would indicate a problem outside the braking system but in some way affecting the braking system. You could be mistaking your problem for something else, it's very easy to do since there are so many systems and components that rely on each other to function properly.

Keep me posted.

-Jeff