W123 Brake Master Cyclinder

[fatherpierre]

As per the title, mine has failed. No resistance and pedal to its lowest point but brakes still working.

With this in mind:

1. Is cyclinder failure the only thing that could cause this? This symptom came on over a few days and now even pumping the brakes fails to get the resistance back. Brake fluid is good.

2. I have a 1980 pre-facelift 230, the carb model with no ABS. I'm having trouble getting an answer from the people at Eurocarparts (or google!) as to whether the part is the same as on the facelifted, injected cars.

These pre facelift models seem to have been forgotten about in terms of computerising the parts searches, but most non engine parts seem to have been carried over, so I'm hoping the brakes were too.

Thank you.

 

[Marku]

Well where to start? Assume all else working OK no leaks, fluid levels, pads etc? Is the vacuum OK? Could be cylinder seals but if the brakes work in all other respects would seem unlikely and sounds like lack of pressure so back to checking the vacuum connection. If all else fails try Mark Cosovitch at 123 World. I am told that there is nothing he does not know about the 123.

 

[jaymanek]

Sounds like master to me, replaced mine a couple of times now...

 

[Ted]

Reported

 

[grober]

http://mb.bolinko.org/wis/w123/CD01/Chassis/42-310.pdf
details the seal between the master cylinder and vacuum diaphragm.
might be problem but can be indicative of impending master cylinder failure.
This section deals with the brakes
W123-dokumentacja cz. 1
Another possible cause of long pedal travel might be a sticking caliper piston but this should give rise to a discernable drag on one or more of the wheels. If you jack up each corner in turn then apply the footbrake followed by spinning the wheel you should be able to check for this on each caliper.

 

[fatherpierre]

Thanks. I will have a look at it tomorrow. The brakes are A1 in terms of performance; there's just no pressure in the pedal and long travel. Pumping them initially brought back the pressure, but that's now gone, so I'm assuming it's a leak.