monkie Posted September 22, 2019 Share Posted September 22, 2019 Back in April I changed the brake fluid reservoir as I split the old one. There was a lot of crud in the system. I fitted a new reservoir and bled the whole system. Since then I have noticed the amount of pedal travel seems to be increasing. I have adjusted the rear drum brakes and this made no difference. I also can't see and leaks of brake fluid. The brakes aren't spongy, the fluid was new out of an unopened bottle. I did a search on the forum and one suggestion was a worn master cylinder. This would make sense from the amount of muck that was in the system. What checks can I do to find the problem? Quote Link to comment Share on other sites More sharing options...
western Posted September 22, 2019 Share Posted September 22, 2019 Try adjusting the servo pushrod that acts on the master cylinder piston. Only muck in the system would be from failing seals which make the fluid black. How old is the master cylinder.? 1 Quote Link to comment Share on other sites More sharing options...
monkie Posted September 22, 2019 Author Share Posted September 22, 2019 Thanks Ralph. I think the cylinder is original. I've done nothing to it in the 10 years I've had it. The fluid was black and the seals from the old reservoir were in a right state. On reflection I probably should have replaced the lot, but I don't just want to start randomly throwing new parts at it without understanding the problem. 1 Quote Link to comment Share on other sites More sharing options...
Snagger Posted September 22, 2019 Share Posted September 22, 2019 Have someone pump the pedal hard while you watch the hoses - you could have one or more ballooning. 1 Quote Link to comment Share on other sites More sharing options...
monkie Posted September 22, 2019 Author Share Posted September 22, 2019 7 minutes ago, Snagger said: Have someone pump the pedal hard while you watch the hoses - you could have one or more ballooning. Thats a good tip. I'll give it a try. Quote Link to comment Share on other sites More sharing options...
monkie Posted September 23, 2019 Author Share Posted September 23, 2019 I had a look at the rubber hoses while someone pumped the brake pedal and all is in order. Regarding the pushrod: I haven't made any adjustment yet, but would this explain a gradual deterioration over a few months which I think is getting worse? Given Ralph's comment of black residue in the old reservoir coming from deteriorated seals and the fact that I noticed corrosion in the master cylinder, do you agree that this would be a wise move: https://www.paddockspares.com/nrc8690g-brake-master-cylinder-110-130-non-abs-to-ha901219-trw-lucas.html Quote Link to comment Share on other sites More sharing options...
Snagger Posted September 23, 2019 Share Posted September 23, 2019 It does sound like a leaky master cylinder. As long as it’s a genuine cylinder, then you should be ok, but even Lucas/TRW quality is spotty. But you stand a much better chance than with Paddock’s usual supplier. Quote Link to comment Share on other sites More sharing options...
monkie Posted September 23, 2019 Author Share Posted September 23, 2019 Thank you, I had a look for my options and can only find the Ferrodo one. I did however find it much cheaper on LRSeries site. I'm going to get it and see how I get on. Is it a bolt on replacement, or do I have to make adjustments to the servo pushrod? Quote Link to comment Share on other sites More sharing options...
Snagger Posted September 23, 2019 Share Posted September 23, 2019 If the servo is like on the SIII, then you shouldn’t need to adjust it - they’re supposed to be factory set to a specific resting measurement. Quote Link to comment Share on other sites More sharing options...
monkie Posted September 23, 2019 Author Share Posted September 23, 2019 I've ordered the ferodo master cylinder. I'll fit it at the weekend and see if there is an improvement. My new fluid reservoir has got black crud in the bottom so I'm sure the seals are breaking down. Quote Link to comment Share on other sites More sharing options...
western Posted September 23, 2019 Share Posted September 23, 2019 Think you will find a huge improvement. Quote Link to comment Share on other sites More sharing options...
monkie Posted September 28, 2019 Author Share Posted September 28, 2019 Replacement master cylinder (Ferodo) arrived in the post. Fitted this morning and taken on a test drive...... As you thought Ralph, a huge improvement. Pedal travel is now what I consider normal, I can hold it on a hill on the pedal without it slowly sinking to the floor. Thank you both for your advice. 3 Quote Link to comment Share on other sites More sharing options...
Snagger Posted September 28, 2019 Share Posted September 28, 2019 Glad it was a simple fix. Quote Link to comment Share on other sites More sharing options...
western Posted September 28, 2019 Share Posted September 28, 2019 That's good news. Quote Link to comment Share on other sites More sharing options...
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