What could cause brake pedal to go to floor after brake service?
 

friends 77 240D, they took it to a corner brake shop, had front calipers and hoses replaced. a few days later while braking, the pedal went all the way to the floor, pumping it restored the brakes. has been happening off and on since then. i told them sounds like a bad MC, maybe the shop incorrectly bled the brakes and overran the seals in the MC... anything else to suspect? could incorrect brake hoses cause this? fluid level is fine and doesnt seem to be disappearing.

Sometimes, all it takes is a good dose of fresh brake fluid to do in a tired master cylinder.

exactly! the master cylinder is toast....probably from the flush....have a hard time believing they bleed the system via the pedal method.....you can't blame them for a 35+ year old master cylinder for failing....

i should mention the MC is only 2 years old though

Regardless of what the shop did, a good master cyl should tolerate full stroke. Rebuilt masters usually have a pretty rough bore, this leads to rapid seal wear. Wet fluid can corrode the bore pretty rapidly causing the same effect.

Changing the fluid is sometimes a short term fix, ( new fluid has fresh seal swelling additives )

If the hoses don't leak, they are not the cause of the problem.

Don't drive the car, change the master cyl.

i mean, i agree and from the symptoms and my own experience with a failed MC, thats what i think it is. what if the calipers were not bled. what kind of symptoms could that cause?

You would have a low pedal every time.

thanks for replies! was hoping to track down a problem that would have been cheaper than another master cylinder :D

Your probably going to have to figured out the problem on your own....check the obviously, fluid level...and leaks.....then rebleed the brakes....and then if its still not fixed its the mc...

is this a manual? if so, its possible the slave cylinder is leaking or the clutch wasn't bleed correctly...

oh yeah should have mentioned that, it is an automatic

Answer
 

If there is no fluid loss = the master cylinder is bad.
http://www.peachparts.com/shopforum/diesel-discussion/347318-brake-system-bleeding-master-cylinder-bleeding-damage-warning.html

.