Lost most of my break pressure.. Master??

turbonator · Post by **turbonator** » Thu Oct 07, 2004 3:38 am

I just lost about 80% of my breaking the pedal just sinks to the floor.. Today it started making noises and the clutch and break pedal started vibrating when I touche the break pedal.

I've lost no fluid. I think it's the master but dont know for sure..

Any ideas..

Thanks.

THAWA · Post by **THAWA** » Thu Oct 07, 2004 3:58 am

could the booster be at fault?

BAC5.2 · Post by **BAC5.2** » Thu Oct 07, 2004 4:58 am

Anything weird happen? Did you drive really really aggressively or anything?

professor · Post by **professor** » Thu Oct 07, 2004 2:04 pm

The master cylinder is leaking past the piston seals internally. Nothing else would cause a sinking pedal. A booster issue would give a very hard pedal but no sink.

Replace it and also thoroughly flush your entire brake system, bleeding at each point (master then fronts then backs and repeat). All that crap from the bad cylinder is now loose in your system, and it may be bad fluid that took down the mater in the first place.

Don't drive the car until fixed, obviously. You may have a little braking now but it won't last.

Post by **Legacy777** » Thu Oct 07, 2004 2:39 pm

I'd probably concur about the master cylinder being bad, however I'm a little confused about the clutch and brake pedal vibrating when you hit the brake pedal all of a sudden.

Something's not really adding up here...

professor · Post by **professor** » Thu Oct 07, 2004 4:01 pm

This would really be strange, but are you sure the pedal assembly is firmly mounted ? I broke the spring return assembly on a car once and the clutch and brake pedals suddenly felt very strange, but no sinking pedal. That problem was easy to diagnose as half the sping landed on my foot.

It is possible that the master cylinder piston lost one of its seals entirely, and is now gouging its way along the bore, causing the vibration. It would be seized if not forced along by 500psi of motive force, enough to cause plenty of vibration.

I've seen a few masters begin to feel bad, making the pedal travel not so smooth, but I'm not sure I'd call it vibration. Usually in that case the master bore is pitted beyond rebuild capabilities, and the cylinder slides poorly and roughly. A British car specialty.

Hate to bring it up, but if one of your calipers is getting ready to shit itself, it could cause the same type of feel, and may take your master with it due to higher than normal pressures. An eroding caliper often damages the master, it is surprising that the bad stuff makes it through the system but it does. How does your fluid look ? If something is going bad wrong the fluid will look like crap.

turbonator · Post by **turbonator** » Sat Oct 09, 2004 3:03 pm

Thanks guys.. So how much $$$ I'm I looking @ here I will try to find a used master.. Also how much labour is involved.??

The vibration I'm talking about is when my foot first touches the pedal it makes a small vibration then just drops to the floor.. And it is slowly getting worse. There almost completly gone..

I've only had the car for a year now and when I first got it I lost all break pressure which I fixed by refiling the brake fluid.. But it's been fine ever since and now I seem to have all my break fluid..

This sucks I was just about to replace some axles and now this..

turbonator · Post by **turbonator** » Mon Oct 11, 2004 2:51 am

professor · Post by **professor** » Tue Oct 12, 2004 2:25 pm

a master cylinder is the last thing I would buy used

Post by **Legacy777** » Tue Oct 12, 2004 5:45 pm

why?

They really don't go bad IMO if you change fluid regularly. I've swapped MC's around, and sold the one I had.

professor · Post by **professor** » Tue Oct 12, 2004 6:18 pm

If I knew the provenance of the cylinder it wouldn't be so bad to take a chance...but who says the guy who had the now-junked car ever changed the fluid, much less regularly? Not to mention, cylinders of all types suffer badly from disuse, especially if allowed to go dry. We're talking about 12 year old safety parts here.

Used $30 New $110 its an easy call unless I have a good used on on my own shelf. And I can get the new one in 15 minutes.

dzx · Post by **dzx** » Wed Oct 13, 2004 8:42 pm

could the vibration be a wheel bearing?

turbonator · Post by **turbonator** » Mon Oct 18, 2004 5:53 pm

Well I have a prety fast leak cause I'm losing all my brake/clutch fluid within a few weeks now. Where should I start to look.. Does this mean the master is leaking? cause if it was a brake like or caliper would it just lose brake fluid?

Post by **Legacy777** » Mon Oct 18, 2004 6:43 pm

You're losing clutch & brake fluid?

They're two completely separate systems.

turbonator · Post by **turbonator** » Tue Oct 19, 2004 11:36 pm

oh.. It was the big container near the master. It was empty and my clutch felt much better after I filled it up.. and my brakes came back.

I thought it was like my bimmer which runs of the same system for both.

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Lost most of my break pressure.. Master??

Lost most of my break pressure.. Master??