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General Tech TR4A Brake Master Cylinder

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KVH

KVH

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I installed a new brake master cylinder 13 months ago and it’s now leaking all over my shoes. I keep forgetting the rule with these things. You’re supposed to replace the brake master cylinder at least once each year, but rebuild it at least every 3 months, correct? I really need to stay on top of these things.

Sheesh. Gasp. Smile, go on and enjoy . . . .

Fortunately I’ve got all I need in my parts cabinet. Please don’t tell me I can’t use Dot 4 Synthetic. I think I’ve been all over that issue before.
 
KVH said:
I installed a new brake master cylinder 13 months ago and it’s now leaking all over my shoes. I keep forgetting the rule with these things. You’re supposed to replace the brake master cylinder at least once each year, but rebuild it at least every 3 months, correct? I really need to stay on top of these things.

Sheesh. Gasp. Smile, go on and enjoy . . . .

Fortunately I’ve got all I need in my parts cabinet. Please don’t tell me I can’t use Dot 4 Synthetic. I think I’ve been all over that issue before.
Click to expand...
Even with these units, I still practice the ----If it isn't broke don't fix it. With 3 TRs and 2 to 10 years on each and no leaks. BUT there was a TR3B before the 3 present TRs, that did have a leaky master and after giving the car to my son. It had another leak.
Charley
 
Leaking on your shoe is part of the brake failure warning system.
 
Bummer. Bad parts strikes again!

I have used DOT4 in everything without trouble. I think we decided it would only be an issue in very humid climates, where it cannot absorb any moisture in the brake system.
 
Should be no problem whatsoever using Dot4 brake fluid - assuming either Dot3, Dot4 or Dot5.1 were in the braking system before. The previous owner of my TR4 had rebuilt the system and used Dot5 fluid, with silicone formulation, which should NEVER be mixed with the glycol-based Dots3, 4 and 5.1 ... as rubbers can be affected. There is an appropriate warning by my master cylinder!
Braking fluids DOT 3, DOT 4, and DOT 5.1. are hygroscopic or absorb water and that is why brake fluids have two boiling point values. On the other hand, DOT 5 is a highly hydrophobic silicone formulation, or it repels water, making its boiling points more stable (260 °C dry boiling point and 180 °C wet boiling point).
I suggest if fluid is leaking over your brake shoes - and if all is as it should be from the above - then you have a coincidental issue with the slave cylinder which is easy enough to replace, or repair with new rubbers if the bore is still up to it.
 
If your car is COMPLETLY painted ,done and sorted the Dot 5 silicone fluid is the best. However,
silicone magically gets everywhere and will cause severe problems if you have to do ANY respraying.
NEVER use it around a project car. The biggest upside is it will never damage your firewall.
Mad dog
 
Apologies, KVH mate ... I must have a one-track mind - I see now when you said shoes, you meant footwear not brake shoes!!
I've just been looking at other posts on master cylinders ... there's no chance that your new master cylinder is not mating properly with the flare on your brake pipe? I was reading that some earlier (ie, TR3) after-market MCs were being delivered with a black machined adaptor on the output - possibly for thread adaptation but maybe also for brake pipe flare matching. It's absolutely vital that the flares match - you should be able to tell by looking carefully into the MC outlet whether it should receive the concave (ie, mushroom-looking) or convex end of your brake pipe.
I'm sure Mad Dog will be along in a minute to confirm! Cheers...
 
I’m just not sure what makes them go bad so fast. Some last five years or more, others not. And, BTW, I have three really great rebuilt kits for .750 bore; the problem is that every one I buy is .70 bore. I may buy new kits, but at $14 plus shipping for kits, and $30 for an after-market new one, I have to wonder.
 
If my memory is correct and long term is not so bad, the 1960 TR3 that I bought used, rebuilt, and cheap in 1963, and that was my only driver, went 10 years and 100k plus miles on the original untouched master cylinder. And it never dripped on my shoe. (The speedometer cable did that.)
 
I know. There are some things that were once really good, and whether it’s the fluid, the workmanship, or whatever, I hope competition keeps the quality steady. Fun old cars.
 
I went looking for champion spark plugs for my TR4. But none of the over 40 local outlet and franchise auto stores carried them, except for about three. You might guess where they were located.

They were In those special parts of town where people still work with their own hands, own aging and classic vehicles from the 60’s and 70’s, are generally considered “blue collar,” and like to fix their own things.

People who know how cars were built, understand the auto trades, and don’t roll their cars into the river bed when there’s a mechanical issue.
 
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