Dave Ashworth Posted June 17, 2017 Report Share Posted June 17, 2017 Dear all, Well, what a day for issues, first the PRV and now an ongoing problem with the brake master cylinder. The master cylinder is a recent TRW replacement one. There were no issues for several weeks of use, over 1000 miles, until recently. Something in the system is creating a vacuum to the point where the screw cap on top of the master cylinder is now concave as opposed to slightly convex. Sometimes the reverse happens and I open the bonnet to find that quite an amount of brake fluid has actually been expelled, possibly under pressure, from the master cylinder. The brakes have been bled several times. The fluid is all new. I've even drilled a tiny hole in the inner cap that clips into the main reservoir cap to help breathing. Just home from a short drive (25 miles) and the cap is vacuumed hard down again, so hard that it is impossible without great pressure to remove the cap. Any ideas on this issue would be greatly appreciated. Thanks for your help. Dave. Quote Link to post Share on other sites
pfenlon Posted June 17, 2017 Report Share Posted June 17, 2017 Has to be something in the servo Dave. Sorry I'm not too well read with them to help more, but Stuart will nail it for sure. Where's me biscuits? Quote Link to post Share on other sites
Dave Ashworth Posted June 17, 2017 Author Report Share Posted June 17, 2017 Your biscuits are on my kitchen workshop and I have resisted eating them for almost two weeks now. You'll get them soon. Lol. Dave. Quote Link to post Share on other sites
Andy Moltu Posted June 17, 2017 Report Share Posted June 17, 2017 (edited) Doesn't the cap have a breather hole let air in? Has yours become blocked? Edited June 17, 2017 by andymoltu Quote Link to post Share on other sites
Waldi Posted June 17, 2017 Report Share Posted June 17, 2017 If the fluid disappears I can image the servo (vacuum) pressure sucks it out. That would also explain the hollow reservoir cap. Quote Link to post Share on other sites
Guest ntc Posted June 17, 2017 Report Share Posted June 17, 2017 Welcome to the world of naff replacements Dave the cap should be vented think you will find the push rod has not been setup right. Quote Link to post Share on other sites
Dave Ashworth Posted June 17, 2017 Author Report Share Posted June 17, 2017 Yes the cap is vented, as is the clip-in cap inside the outer cap, but I drilled an extra little hole in the inner one to make sure. Thanks for your help. Dave. Quote Link to post Share on other sites
Dave Ashworth Posted June 17, 2017 Author Report Share Posted June 17, 2017 Neil, does this mean that the push rod can move? Everything was fine more than a 1,000 miles, then the issues began. As to Waldi's point. Does this mean I need a new servo? Cheers. Dave. Quote Link to post Share on other sites
openroad Posted June 18, 2017 Report Share Posted June 18, 2017 Good to hear that you are out and about in your 5 Dave, hope you get these weird problems sorted. Conrad. Quote Link to post Share on other sites
Dave Ashworth Posted June 18, 2017 Author Report Share Posted June 18, 2017 Cheers Conrad. I've done 1500 miles in it so far and supposed to be going to France on Friday with TR Register tours, but last night I started reassembling the 4 just in case I can't sort it in time. I'll finish that today with some luck. Cheers Conrad. Dave. Quote Link to post Share on other sites
stuart Posted June 18, 2017 Report Share Posted June 18, 2017 Odd problem Dave, do the brakes release properly or are they still on when this happens? Stuart. Quote Link to post Share on other sites
Dave Ashworth Posted June 20, 2017 Author Report Share Posted June 20, 2017 Hi Stuart, Thanks for your question. The brakes seemed to function fine, although the pedal was a bit soft. I've replaced the servo today with an original from Fitchetts. I'll bleed them in the morning and see what happens. Thank you one and all. Let's see what happens tomorrow. At lease everything is new now, so I could be in with a chance. Cheers. Dave. Quote Link to post Share on other sites
Waldi Posted June 21, 2017 Report Share Posted June 21, 2017 Dave, As indicated by Neil above: did you check the clearance (depth) of the push rod in the servo? It is adjustable. To be honest, I think it is an indirect measurement, because not the actual clearance between MC piston and servo push rod is measured, just the depth of the push rod in the servo. Maybe the more knowledgeable people can explain? Regards, Waldi Quote Link to post Share on other sites
Dave Ashworth Posted June 21, 2017 Author Report Share Posted June 21, 2017 HI Waldi, Yes, I checked the clearance and it was fine. Forgotten what it was now. I put the new servo on and the brakes are fine now. A good solid pedal, so it must have been a servo issue. Thanks one and all for your help. Dave. Quote Link to post Share on other sites
ianhoward Posted June 21, 2017 Report Share Posted June 21, 2017 Hi Dave Pleased you're up and running! Hope all's well! Cheers Ian Quote Link to post Share on other sites
openroad Posted June 22, 2017 Report Share Posted June 22, 2017 Have great Trip Dave....I look forward to a friendly cuppa , and to hear how you got on.. You have worked hard on that 5, many years of Happy Motoring ahead ! All the best, Conrad. Quote Link to post Share on other sites
Waldi Posted June 22, 2017 Report Share Posted June 22, 2017 Dave, Enjoy France, the food, peolpe and your TR5! Waldi Quote Link to post Share on other sites
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