Brake Master Cylinder Reservoir Nappy

[Guest]

Yes, my brake master cylinder reservoir must wear a diaper. After a run, my reservoir sweats brake fluid from beneath the cap and I am forced to place a diaper-like paper towel around the cap perimeter to absorb that dastardly, paint-eating brake fluid. I have tried overtightening, undertightening, a new cap, a new reservoir, a new gasket, a double gasket (don't ever try that). All to no avail. Does anyone else have this problem or have I been communicating with Tinster too much?

 

[hondo402000]

have you tried pumping the brakes in the drive way and having someone watch the MC and actually see what is going on? I have found things aren't as they apear sometimes, might give you a hint of where it is comming from

 

[70herald]

Bill
Are you perhaps overfilling the reservoir? As the brakes heat up, the fluid expands, and the level in the reservoir goes up.
this problem is particularly acute with disk brakes since they have a fairly large volume of fluid in the caliper which gets hot.
On the Heralds for example disk brake cars got a special reservoir expander because the extra volume of fluid in the brakes is to much for the standard reservoir when the fluid heats up.

see what happens if you only fill the fluid to the minimum with cold brakes!
Yisrael

 

[tomshobby]

Bill,

Is it possible that the fluid is squirting onto the underside of the cap when you release the brakes?

 

[Scott_Hower]

Is it possible that the cap should be vented (usually a pinhole) and the vent is plugged?

 

[Tinster]

'Morning Bill-

Wendy's got me packin' for the grand escape to Aruba.

I'm probably not in a position to offer advice on anything
to do with TR6 braking systems but I offer this observation.

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My master cylinder does not leak. Yes, of course it sees very
little use with Crypty up on jacks all the time.

I took the cap off just now and observed the following.

The fluid level is about 1/4" below the top edge of the
white plastic, twin chambered container. Actually, level
with the chamber divider.

My cap was on finger tight only.

My cap has a very tiny hole right dead center. The hole in
my cap is open and I can blow air thru it.

Maybe take a look at your fluid level and see if the tiny
hole in the cap is open.

d

 

[pa297pass]

Bill:

Mine leaks the same as yours and I have never been able to correct it. I too have a "nappy" to soak up the fluid.

I have tried a new reservoir and cap to no avail. I find if the cap isn't overtightened it seems to leak less.

Good luck and I'll be interested in what you find.

Matt

 

[swift6]

I would check the pinhole in the cap and make sure that it is actually open. A hot sewing needle can open it up nicely without oversizing it.

 

[DNK]

Wear gloves!