Spitfire & GT6 Forum

Hi

I have a strange leak on my master brake cylinder on my 1500. Its fitted with a GMC224 MC with large reservoir. Since I’ve had the car I’ve noticed that the paint beneath the MC is being worn away by brake fluid but I’ve never been able to find the leak until today. I noticed a small drip on the underneath lip of the MC cap, the rest of the MC looks in tact and is fairly new. Even thought the car has been stood for two weeks there is still a small drip forming.

I’ve looked for a replacement seal and cap but they aren’t available. I’ve been told the GMC224’s are very difficult to get hold of and I should fit a GMC205z (Canley classics). Has anyone fitted one of these and was it okay?

Ideally I’d just find a way of sealing the cap, it seams a big job replacing the MC and bleeding the whole system for a leaking cap. I also wondered as the thread is on the external face of the reservoir could I put some plumbing tape to seal it, Thoughts?

Thanks in advance.

I am wondering why it would be leaking from the cap in the first place. Is it overfilled? There is usually a vent hole in the cap for venting so it is funny that it would want to leak around the threads. There should also be a rubber seal that seals the cap so that the liquid cannot get to the threads, is it missing from inside the cap?
Dan

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Dan Aycock
Walla Walla, Wa.
Yellowhawk Valley Spitfires
69, 69, 72, 75, 78, 79 Spitfires
TRF# 006047

Likely leak is between the metal body and plastic reservoir.

There is a definite small leak at the underneath of the cap, The rest of the cylinder looks fine. The reservoir is not over filled. I've attached a photo of the cap and the only seal it has, there is also no vent hole.

David , What your describing is identical to my issue. Finding brake fluid, what appears to be leaking just under the cap. I recently purchased a new rubber seal for under the cap. I am not totally convinced that it solved the problem. Has helped a bit. Not really keeping a eye on it , I have the drip trays installed.
If you look close I think you will find a very small hole on top of the cap. This is where I believe its coming from and flowing over the cap edges.
Its a mystery .
I even made a cork gasket and added it to the rubber gasket, no improvement

http://www.ebay.com/itm/NOS-British-Ley-Brake-Master-Cylinder-Cap-Gasket-Triumph-TR250-TR6-Spitfire-GT6-/301718016990?hash=item463fcb93de&vxp=mtr



Edited 2 time(s). Last edit at 2015-09-08 03:23 PM by tymnmony.

Stumbled on this while looking for a replacement cap for my spitfire. I am having the exact problem on my 73 with a large cap. Did you ever resolve your problem?

I was hoping for an easier and cheaper solution.

All, I'm sure you have probably solved this by now, but i thought I'd add my solution just in case others run into the same problem.
This summer I took my spit on a 3000 mile tour of Europe. every day I did engine oil, clutch and brake fluid checks. I would often take the lid of the brake and clutch because it was hard to tell through the plastic.
Now, as I was descending into Italy,through the Alps from Isola 2000, my brake pedal started to dip very low. it was a 2000m descent, and I was making a point of not riding the brakes, and using engine braking where possible. I got to the bottom, and pulled into my first Italian petrol station. upon lifting the bonnet, i was greeted to brake fluid all over the bulkhead. i checked the m/s and I had not blown a seal as there was no fluid inside the rubber boot, and there was no weeping from the base of the reservoir- it had all come out of the cap.
What I found was that when I had done my morning checks, I had not put the cap back on properly, and as I was descending the mountain the harsh negative angle had pushed the fluid up against the lid, and caused it to leak out. Now I know this may seem a silly mistake-but make sure, especially if you have an aftermarket m/s, that the lid is on properly. you may screw it on, but often you can push it down and a second audible click is heard. the thread isn't all that good on them and if it isn't on perfectly straight and not cross threaded any movement in the car will cause it to slop out.
I hope this helps some, and reminds others!
Rowan