Master Cylinder problem??

[XWL61]

Hi All

Before I rush out and buy a new master cylinder, I want to run these symptoms past the collective expertise of this messageboard.

Recently Muriel's brakes started to bind, so I had all the drums off and checked everything over - All ok - no seized cylinders, rear cylinders not binding on backplate, brake pedal adjustment ok etc etc. replaced rear brake hose whilst I was at it. Put it all back together - everything hunky dory.
Today problem re-occurred, initially on the rear os. To free it off I opened the bleed nipple - bingo!. Off I went on my merry way. A little further on, same problem. Brake pedal also becoming harder. Same solution. Later on it was clear more than just one brake was binding - the ns front hub was hot. Opened bleed nipple - hot gaseous brake fluid spewed forth.

I am guessing a seal in the master cylinder is not working and pressure builds up in the system everytime I press the brake pedal hence the binding brakes.

I await your diagnoses

Andy

[bmcecosse]

Assuming you don't have a servo, there is probably not sufficient free-play in the pedal to master cylinder linkage. Also possible (actually more likely when I think about it !) that the return spring has failed... Lift the little floor plate and inspect

[XWL61]

No servo, sufficient play in linkage and spring still springy!

[bmcecosse]

Must be the master cylinder then....... You don't have front discs I assume?

[XWL61]

No discs, so not the problem of the bit that should be removed! Standard system.

Time to shop I guess!

[kennatt]

Are you 100% certain that the pedal is releasing,because the symptoms are exactly the indication of a pedal that is not adjusted .What hapens if, when the problem starts,you pull the pedal back with your hand,do the brakes still stay on.

[bmcecosse]

[XWL61]

It was the master cylinder! The rubber boot had split and there was a fair amount of crud and rust around the end of the piston which would appear to have been preventing it from returning fully on occasions.
The drain hole in the chassis leg below the m/c was also blocked which probably didnt help things either.
Good clean up of the area and a new m/c and the brakes are fine!

[bmcecosse]

Well done !

[rayofleamington]

The drain hole in the chassis leg below the m/c was also blocked which probably didnt help things either.

That's pretty common - it's worth to get under the car a few times a year and poke a pipe cleaner through all the drain holes sills,
box secions, chassis legs, doors etc..
They all have a function and if blocked, you're likely to get nasty corrosion (especially if it's not full of waxoil - mine never are )