Brake mc elusive fluid leak

[NoviceM]

I have replaced the original mc with a new one from ESM after first removing too hat valve as required with front disc brakes. Brakes bled fine, nice good pedal action. I fitted an extension brake resevoir.
BUT....I have a tiny fluid leak coming from SOMEWHERE in the mc. Have inspected as best I can underneath using dental mirror, doesn't appear to be copper washers either side of banjo. Doesn't appear to be the front end of the mc either, nor the original filler (vent has been stopped off)
.......
But there is no where else it can be coming from.i am frustrated....spent over a week looking for source of this tiny leak (4 drops per 24 hours) Anyone got a flash of inspiration.

[philthehill]

Could it be leaking from the upper rear master cylinder plug which has been replaced by the plug with feed pipe from the remote reservoir.
Check also the tightness of the jubilee clip holding the pipe onto the plug with feeder pipe.

[NoviceM]

Thanks for that, but I have checked both these, and they seem innocent. Part the problem is brake fluid doesn't show up visually verty well. To detect the leak I put a small piece of white card beneath the mc, on the floor of the chassis member....but of course the fluid will probably run to lowest point of mc body before dripping onto card.

[Bill_qaz]

Are you sure it's not residual from your work, clean the area with brake cleaner, does the fluid level drop in your remote resevoir?

[NoviceM]

Good point......I will leave it a few days .....in case it is residual and recheck. Level drops very very slowly, if at all.

[shelterdrown]

I also tried cleaning with brake cleaner, the fluid level in the remote reservoir decreased significantly.

[paul 300358]

Sorry if I've missed it but are you sure that the cap is a non vented cap. If it is a non vented cap, is it well sealed to the body of the mc. When using a remote reservoir the should only be half full due to the airlock above the inlet pipe.

[Jim McCrae]

Check the tubing from the remote reservoir. The plastic tube supplied with some kits is really not up to the job. After installing a kit on my Traveller I had continual leaks caused by fluid sweating through the tubing. I solved this by replacing it with proper brake fluid grade EPDM. This is quite expensive but it does the job.

Good luck.
Jim