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View Full Version : Brake Master Reservoir Weeping.......again



02-07-2008, 06:32 AM
I had a problem with my brake master reservoir weeping brake fluid from beneath the cap. No matter how tight or loose it was. Smart me I tried a new gasket, then a new cap, then a double gasket (like that worked!), then a whole new reservoir/cap/gasket combo. It still weeps. I have taken to keeping a diaper around the perimeter of the cap. Sweat bands work well. It is obvious when I look down on top of the translucent cap that the rubber gasket never quite seals. Anyone have a fix for this? Perhaps making up my own gasket from a slightly thicker rubber? These things have got to be all warped from the manufacturers. I have seen this before. Very frustrating as I use Dot 3, which would love to dribble down onto my paint.

At least colorful wrist bands make it rather festive under my bonnet.

LastDeadLast
02-07-2008, 07:27 AM
Bill,

I've had two different MC's and they both did same as yours.. I figured it was the price of admission.

I'd like to know a "fix" for this one too, if it exists.

DrEntropy
02-07-2008, 07:44 AM
Curious: Can you tell from the gasket if it's even being pressed into contact with the 'lip' of the rezzy? You say it never quite seals...

With the gasket out of the lid and wound "home" on the bottle, does it hit on a shoulder on the bottle's O.D.? Could you relieve the I.D. of the cap by chamfering it at the point where it hits and stops?

The other thought is: could the lip of the container be less-than planar at its circumference?

02-07-2008, 07:57 AM
The other thought is: could the lip of the container be less-than planar at its circumference?


That's pretty much what I have deduced. Looks like they are injection-molded, and poorly done at that. My have to "shave" the lip flat with some sort of device.

Bummer.

DrEntropy
02-07-2008, 08:10 AM
To be a thorough PITA, my "solution" would be to remove it from the car, get a ~flat~ surface (like a piece of marble or steel plate) and some #600 Wet-or-Dry sandpaper and "lap" the edge by holding the thing upside-down and slowly evening out the lip with "figure eights". Water would work as a lubricant.

Caution here: do NOT use Herself's marble countertop if there's ANY residual brake fluid likely to drip out. You'll pay, trust me.

EDIT: Just had a thought! Use that old flywheel as the flat surface!! /bcforum/images/%%GRAEMLIN_URL%%/wink.gif

Andrew Mace
02-07-2008, 09:45 AM
Bill, Shannon: were these new(ish) cylinders and reservoirs? did the weeping start right "out of the box" or were they on the car for some period of time before the weeping started? I've never owned a TR6, but the dual master cylinders on GT6s and Spitfires are very similar in design, and I don't recall ever having such a problem.

Rickc
02-07-2008, 11:17 AM
........ It is obvious when I look down on top of the translucent cap that the rubber gasket never quite seals. Anyone have a fix for this? ......

Bill,
When I tighten mine back down, I can clearly see the rubber gasket getting evenly compressed around the entire circle. Since yours does not seem to be getting evenly compressed then I would agree with dre. Maybe if you have a small piece of flat stock steel, you might be able to determine "out of flatness" (sorta'speek) without having to remove it....but then you will need to remove it if you need to do a little sanding. Will be interesting to hear if this is an old or newly installed MC reservoir.
If you where to make up a new gasket, it would have to be thicker and much more pliable that OE material.
Rick C

TR3driver
02-07-2008, 11:20 AM
To be a thorough PITA, my "solution" would be to remove it from the car, get a ~flat~ surface (like a piece of marble or steel plate) and some #600 Wet-or-Dry sandpaper and "lap" the edge by holding the thing upside-down and slowly evening out the lip with "figure eights". Water would work as a lubricant./bcforum/images/%%GRAEMLIN_URL%%/iagree.gif Except I don't think you need such a good surface in this case ... MDF will do fine; and I'd use coarser dry paper. I actually touched up my Stag reservoir "by eye" with a machinist's file and it now seals fine. Dunno if it's possible on the TR6, but with persistence the Stag reservoir can be removed with the MC still on the car.

Rickc
02-08-2008, 09:21 AM
Randall
Yes the reservoir can easily be removed but a full brake bleed is in order on re-install.
Good point on the mdf. Bill, What about putting some sort of powder (i.e chalk line powder) or paint or ????? on the surface of the mdf then putting it on the reservoir opening. You might get to see where the "low" spot is and simply take a fine file to it.
Just a thought. Would sure beat having to remove it.
Rick C

TR3driver
02-09-2008, 02:57 AM
Randall
Yes the reservoir can easily be removed but a full brake bleed is in order on re-install.I don't see it that way. If you've not used the brakes, the MC and everything past it should remain full of fluid with no problem. Any air in the passages between the MC & the reservoir will rise to the top when you fill it.

Of course if the brakes are spongy afterwards then you would want to bleed, but I don't think it would be necessary every time.

In my case it was the bottom of the reservoir that leaked, and I discovered the problem before bleeding the system, so I did have to bleed after facing the surface and reassembling.

Tinster
02-09-2008, 05:43 AM
Andy-

Mine was/is brand new right out of the box.
It leaks also.

Bill could you post a photo of your temporary
fix that absorbs the brake fluid?

Doc- #600 grit will cut marble very quickly. A slab
of steel or glass is best . I've been known to use
the Mrs glass top stove for such projects.

d

02-09-2008, 08:14 AM
Bill could you post a photo of your temporary
fix that absorbs the brake fluid?



Dale, any ole wrist sweat band will do. Just pop it around the top where it affixes to the reservoir. The more colorful the better!

DrEntropy
02-09-2008, 09:42 AM
Doc- #600 grit will cut marble very quickly. A slab of steel or glass is best . I've been known to use
the Mrs glass top stove for such projects. d

Dunno how ya figger the sheet of wet-or-dry would abrade the marble if used as a "fat slurface" to level the PLASTIC lip of a M/C... the abrasive side would be facing the work, not the marble. Unless of course you're suicidal. /bcforum/images/%%GRAEMLIN_URL%%/smirk.gif

bobh
02-09-2008, 02:50 PM
Bill, Dale and Shannon,
What type of brake fluid are you using?

In general some fluids have a tendency to creep onto surfaces not covered in the fluid. You'll see this on your dip stick with some oils. The initial reading is higher than the second reading after wiping the stick.
I'm wondering if the 3 of you are all using silicon fluid and if silicon fluid creeps up the sides of the reservoir.

Creep is a good thing in some situations. Penetrating oil is designed to creep. For example;
P7 Penetrating Oil has a low surface tension, which allows it to spread into a very fine film. One 12-ounce can of P7 Oil will cover approximately 300 square feet of surface. This low surface tension allows P7 Oil to "creep" up surfaces against gravity. It will penetrate and coat 16mm of a threaded bolt in 15 minutes. P7 Oil will lubricate tight crevices and loosen frozen parts.

I've used regular brake fluid as penetrating oil. It's one of the best. So I don't know if creep has anything to do with your leaks or if it is caused by something entirely different.

I searched on Silicon creep and found various comments. For example;
https://www.secondchancegarage.com/public/106.cfm
"Silicon fluids were developed in the 1960s. The major advantage of silicon fluid is its absolute resistance to water, making it a "permanent" brake fluid. Its chief disadvantages are a slightly higher viscosity, tendency to "foam-up" during bleeding and refilling, and a high capillary action (its surface tension is lower, allowing it to creep, or spread out, along the walls of the brake components, sometimes causing seepage or leaks.) Most silicon fluid-equipped cars exhibit a softer, "spongy" brake pedal effort."

BOBH