Brakes...everything OK now?

[XK140]

So, the job has been done on the S3 of replacing the servo,and,while I was at it the master cylinder.The servo had the usual rust at the bottom and I reasoned that at 25 years old it made sense to do the m/cyl at the same time.
Again many thanks to our Dutch friend who supplied the parts,they were an exact fit.
No great difficulties in the job but the servo was hard to get off the bulkhead because it was well stuck with mastic so some wire used in cheese-cutter fashion separated the two.Also two of the pipe nuts to the m/cylinder were stuck so the pipes were cut but fortunately there was enough slack to reflare the ends so as not to have to replace the pipes.
Back on the road the pedal feels softer so I believe previously there was some loss of pressure because of the servo rot.The pedal travel feels a bit long but doesn't pump up so I assume we got all the air out of the system...it almost feels if the back drums need adjusting up?...but the handbrake holds OKish and the drums are self adjusting,are they not?

[glenrobbo]

The self-adjusting mechanism relies on a serrated cam engaging with a serrated fixed spigot "wheel". The serrated teeth can wear and then the cam slips instead of engaging with the next tooth. Sometimes dirt can cause this as well.
Strip and clean the mechanism and examine the contacting areas carefully.

If the spigot has worn badly, it is possible to loosen it by careful grinding, rotating it to present an unworn section to the cam, and welding in the new position.
Or replace with new Sierra bits.

This is the rear nearside brake set-up. The toothed mechanism is visible just to the left of the red spring coil.

Edited by glenrobbo on Wednesday 17th June 13:47

[mk1fan]

Always worth checking the drums adjustment.

If the servo was gone then you would have been losing assistance. A working servo will make pressing the pedal easier.

It is also worth checking all the connections to see if any are weeping.

[phillpot]

Despite the pedal "not pumping up" it might be worth cracking the outlet pipe of the bias valve to bleed from there (easiest done with a Gunson pressure bleed), I have a theory that air can get trapped there because of the angle, worked for me anyway. It's surprising how tiny an amount of air will give a poor pedal.

[XK140]

Thanks for the tips,I'll look at the rear drums and also the possibility that there is still some air in the system.

[XK140]

Thanks for the tips,I'll look at the rear drums and also the possibility that there is still some air in the system.

[greymrj]

Good bit more on the rear brake adjusters here;
http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[XK140]

Update.
I work slower than an arthritic snail nowadays so haven't got round yet to checking the rear brake adjustment or the bias valve thing but I suddenly had a flash of inspiration,or should I say desperation at something overlooked...
THE MASTER CYLINDER BLEED NIPPLE ....
So,is air in there do we think or will any have been bled through via the normal procedure?

[phillpot]

Try it by all means but I thought that bleed screw was there just to "bung up" an unused port?



I've never found it necessary to bleed from there, but I have found that cracking the bias valve outlet connection and bleeding from there can help


.

[LawrieS]

I had no handbrake and poor braking performance with excessive peddle travel after doing the body lift.

In the end I had to set the adjusters so the drums needed lightly tapping over the shoes with a rubber mallet, then it all worked perfectly, top marks from MOT tester a few weeks back.

[mk1fan]

Or ressolve your issues by fitting discs to the rear. Hhhmmm now I wonder who has an almost complete kit laying around?