petertrs Posted July 10, 2021 Report Share Posted July 10, 2021 About 3 yrs ago the brake servo failed and I replacaed it with an aftermarket servo from a well known supplier. I then discovered the joys of trying to set the servo output pin to the correct dimension so that the brake response was good, whilst avoiding the brakes not fully releasing. After much measuring and some road testing I achieved this, applied the locktight and breathed a sigh of relief. After several thousand of miles, including a recent trouble free trip to Scotland, all appeared well. UNTIL this week. Travelling down the motorway in busy trafic in the usual reduced lane area, I appeared to be loosing power, followed by unusual wheel vibrations. Being about 2 miles from a service area I decided to stagger on to safety. By this time it was obvious that the front brakes were firmly on and very fried - lots of smoke and melting of paint, seals etc. By the time the very helpful AA man arrived things had cooled and I had slightly released the master cylinder from the servo to get the car rolling. Stripping things out yesterday the brakes and hub bearing obviously need a complete rebuild. The puzzle is what was the root cause? The servo pin setting hasn't moved and the master cylinder tipping valve appears to function/release under air pressure. One suggestion is that the servo is 'creeping' slowly as the vac. isn't balanced in the unloaded position. I have yet to try to replicate/test this. Has anyone else experienced a similar issue with aftermarket servos or other words of advice to add. With thanks, Peter Quote Link to post Share on other sites
CP26309 Posted July 10, 2021 Report Share Posted July 10, 2021 Wow! I didn't realise the Servo was such a complicated thing that needed to be set up! Quote Link to post Share on other sites
aardvark Posted July 10, 2021 Report Share Posted July 10, 2021 Peter - check out my thread entitled “Sticking brakes and Rev limited engine - one problem or two separate problems” posted on 4th June this year. Sounds very similar to my problem. cheers dave Quote Link to post Share on other sites
petertrs Posted July 10, 2021 Author Report Share Posted July 10, 2021 Thanks Dave, I have just read your post and it sounds familiar. It was John in the workshop at TRBitz who advised me how to set the servo a few years ago, but I guess it will now prove to be defunct - but more tests to do! The comment about servo's and silicone fluid in the replies to you were puzzling as I can't see how the fluid gets to the servo unless the m/c is leaking, but will have a look. Peter Quote Link to post Share on other sites
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