Willie Posted June 12, 2021 Report Share Posted June 12, 2021 Hi All, Got back earlier from 120 mile jaunt in South & Mid Wales having successfully tested my new coil. No issues there, but before I put my TR4 in the garage, I checked the engine bay. For the second time in a week I discovered fine yellowish tinted droplets atop the brake master cylinder. Can anyone explain the phenomenon? Pic attached. Best wishes Willie Quote Link to post Share on other sites
RogerH Posted June 12, 2021 Report Share Posted June 12, 2021 Hi Willie, how full is the reservoir? The breather hole does not normally let anything out but if too full and with the rough old roads of Wales t could get agitated out. Roger Quote Link to post Share on other sites
Willie Posted June 12, 2021 Author Report Share Posted June 12, 2021 Hi Roger, I think level is OK. Here's aa shot to confirm. Willie Quote Link to post Share on other sites
RogerH Posted June 12, 2021 Report Share Posted June 12, 2021 Hi Willie, that looks OK. Clean the whole area down and keep an eye on it. It must be coming from somewhere. if it happens again then clean down again and put a piece of sellotape over the breather hole and see what happens next time it goes out Roger Quote Link to post Share on other sites
Willie Posted June 12, 2021 Author Report Share Posted June 12, 2021 Will do Roger. Many thanks for the steer. Willie Quote Link to post Share on other sites
stillp Posted June 12, 2021 Report Share Posted June 12, 2021 1 hour ago, RogerH said: put a piece of sellotape over the breather hole and see what happens next time it goes out Might it be better to loosely tie a plastic bag over the reservoir so the m/c can still breathe? Pete Quote Link to post Share on other sites
RogerH Posted June 12, 2021 Report Share Posted June 12, 2021 10 minutes ago, stillp said: Might it be better to loosely tie a plastic bag over the reservoir so the m/c can still breathe? Pete +1 Quote Link to post Share on other sites
BlueTR3A-5EKT Posted June 12, 2021 Report Share Posted June 12, 2021 On a Girling braked TR 3 the splash proof seal for the reservoir works a treat. Sadly It will not fit the big lid of TR4 brakes cylinder though. If your clutch is splashing it should fit that. https://www.moss-europe.co.uk/seal-filler-cap-splashproof-582-505.html?assoc=603676 https://www.moss-europe.co.uk/media/pdf/582-505_instructions.pdf Quote Link to post Share on other sites
Z320 Posted June 13, 2021 Report Share Posted June 13, 2021 (edited) Hi, in my opinion this reservoir is to full. The brake fluid spashes on the breather hole from below and pressing the brake fluid in the system (by pressing the brake) the hole sucks air in. And when the fluid comes back from the system (giving giving the brake free) the hole blows air out. And spits out the fluid that is in the hole. I would try 10 - 15 mm less fluid. The front brake is self adjusting and has a very little way of travel, but perhaps you take a look at your rear brake adjustment? Ciao, Marco Edited June 13, 2021 by Z320 Quote Link to post Share on other sites
Z320 Posted June 13, 2021 Report Share Posted June 13, 2021 (edited) BTW this is the way damp air gets in contact with the brake fluid and the moisture gets in the brake system, in my opinion no matter what fluid you use - just because of the difference of the moisture concentration there. But this is another discussion....and I'm out of that, you can google this very simple Edited June 13, 2021 by Z320 Quote Link to post Share on other sites
RogerH Posted June 13, 2021 Report Share Posted June 13, 2021 1 hour ago, Z320 said: Hi, in my opinion this reservoir is to full. The brake fluid spashes on the breather hole from below and pressing the brake fluid in the system (by pressing the brake) the hole sucks air in. And when the fluid comes back from the system (giving giving the brake free) the hole blows air out. And spits out the fluid that is in the hole. I would try 10 - 15 mm less fluid. The front brake is self adjusting and has a very little way of travel, but perhaps you take a look at your rear brake adjustment? Ciao, Marco 1 hour ago, Z320 said: BTW this is the way damp air gets in contact with the brake fluid and the moisture gets in the brake system, in my opinion no matter what fluid you use - just because of the difference of the moisture concentration there. But this is another discussion....and I'm out of that, you can google this very simple +++++1 Quote Link to post Share on other sites
keith1948 Posted June 13, 2021 Report Share Posted June 13, 2021 Hi Willie Brake fluid looks a bit dark in colour so wondering when you last changed it? I check the conductivity of mine regularly with one of the conductivity testers you can get from Halfords or online. It measures the water content and tells you if it needs changing. Water in the system might lead to 'boiling' of the fluid with the braking necessary especially in hilly country roads in Wales. This would raise the level in the reservoir. The fluid level looks similar to mine so my first thought would be old brake fluid needing changing. https://www.halfords.com/tools/hand-tools/all-hand-tools/brake-fluid-tester-113633.html Regards Keith Quote Link to post Share on other sites
Willie Posted June 13, 2021 Author Report Share Posted June 13, 2021 Thanks everyone. Fluid is very probably overdue a change. I think the cylinder cap might hve needed to be tweaked tighter. Just did this after returning from a challenging run up Hay Bluff and along Herefordshire's Golden Valley [hilly, tight bends, single track roads]. I attach a couple of shots, although I do not want to promote cars on to Herefordshire's famously empty roads!!. 1st shot Hay Bluff, second is view along the Black Mountains with Brecon Beacons in background. With a lot of firm braking, the boiling theory makes sense. Willie Quote Link to post Share on other sites
Z320 Posted June 13, 2021 Report Share Posted June 13, 2021 Boiling you realize by having no brake. Quote Link to post Share on other sites
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