sudden brake failure - servo? master cyl?
Discussion
ok this wedge is beginning to try my patience...just a bit...engine now running on all 8 so brakes decide to fail just to keep me on my toes! I've had this before on my Mk1 and it was a master cyl, but is there a way I can check which item is at fault?
I noticed last week that brakes had become a bit soft all of a sudden after a long run...hmm...then today they went VERY soft after a blast on the local freeway - so much that the pedal went all the way to the floor! smell of burnt brake fluid too. Pedal now goes to the floor, pumps up a bit then all the way to floor again.
no loss of fluid though, the reservoir is showing full fluid level same as before.
could it be a failed servo?
I noticed last week that brakes had become a bit soft all of a sudden after a long run...hmm...then today they went VERY soft after a blast on the local freeway - so much that the pedal went all the way to the floor! smell of burnt brake fluid too. Pedal now goes to the floor, pumps up a bit then all the way to floor again.
no loss of fluid though, the reservoir is showing full fluid level same as before.
could it be a failed servo?
Master cylinder.
Way to tell is to bleed the brakes - if there is loads of air then the seals have gone. There will be fluid inside the rubber gromet.
It's normally quite possible to run without a servo. Just put a large bolt in the airline feed to the engine (with jubilee clip) to stop engine breathing air.
Brakes should be rock hard and never spongy. Air is compressable - fluid much less so - so standing on the brake pedal for say 30 seconds should produce no pedal deflection or sinking .. unless you have a leak.
Way to tell is to bleed the brakes - if there is loads of air then the seals have gone. There will be fluid inside the rubber gromet.
It's normally quite possible to run without a servo. Just put a large bolt in the airline feed to the engine (with jubilee clip) to stop engine breathing air.
Brakes should be rock hard and never spongy. Air is compressable - fluid much less so - so standing on the brake pedal for say 30 seconds should produce no pedal deflection or sinking .. unless you have a leak.
Probably cup seals in the master cylinder ruptured. Basically your fluid pump of a master cylinder has turned into a fluid stirrer, just pushing the fluid about in the cylinder without pressurising it.
Theres another seal that prevents fluid leaking back past the pushrod and down into the footwell. If that one has gone, you'll find a drained reservoir and a wet smelly carpet! Brakes will go spongy cos the cylinder then ingests air from the empty reservoir.
Theres another seal that prevents fluid leaking back past the pushrod and down into the footwell. If that one has gone, you'll find a drained reservoir and a wet smelly carpet! Brakes will go spongy cos the cylinder then ingests air from the empty reservoir.
Brakes binding boiling the fluid?
Had this happen to me after a run out. The car had been standing a while and the rear brakes were sticking. Pedal straight to the floor coming down the slip road on the M5! No loss of fluid so similar symptons to yourself.New rear calipers sorted it out.
Andy
Had this happen to me after a run out. The car had been standing a while and the rear brakes were sticking. Pedal straight to the floor coming down the slip road on the M5! No loss of fluid so similar symptons to yourself.New rear calipers sorted it out.
Andy
The smell maybe the nylocks holding the rear disc's on.
If the rear brakes bind, they will get very hot, and will melt the nylocks on the rear disc's if they have nylocks. Always best to fit all metal locking nuts or locking washers on disc's
normally when they melt you also get a lot of smoke from the rear.
If the rear brakes bind, they will get very hot, and will melt the nylocks on the rear disc's if they have nylocks. Always best to fit all metal locking nuts or locking washers on disc's
normally when they melt you also get a lot of smoke from the rear.
crackedfinger said:
Hang on a sec if you can smell burning brake fluid then it's leaking near something hot, and it should be obvious where. Is the master cylinder near something hot on a wedge?
I spilt some brake fluid on a hot exhaust manifold a few years ago and thought I was about to lose the car; it flashed into flames instantly.Wedg1e said:
crackedfinger said:
Hang on a sec if you can smell burning brake fluid then it's leaking near something hot, and it should be obvious where. Is the master cylinder near something hot on a wedge?
I spilt some brake fluid on a hot exhaust manifold a few years ago and thought I was about to lose the car; it flashed into flames instantly.Gassing Station | Wedges | Top of Page | What's New | My Stuff