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Re: [TR] A different sort of a brake master cylinder leak

To: jimhearn1@comcast.net, triumphs@autox.team.net
Subject: Re: [TR] A different sort of a brake master cylinder leak
From: Dave1massey@cs.com
Date: Wed, 15 Nov 2006 08:56:22 EST
In a message dated 11/14/2006 9:11:45 PM Central Standard Time, 
jimhearn1@comcast.net writes: 
> I believe that the leak I have from my '74 TR6 brake master cylinder is
> simply leaking where the reservoir attaches to the master cylinder because
> the fluid is all the way up to the base of the reservoir.  What sort of
> gasket material should be used for this or is it not smart to make a gasket?
> If this is the case and I lower the fluid level enough to remove the
> reservoir and replace the gasket without letting air into the cylinder, I
> would think that I shouldn't need to bleed anything.  Thanks for any help,
> 
There are O-rings sealing this interface.  The proper fix is to replace the 
O-rings which come with the rebuild kit.  Another possible cause is rust in the 
recesses for the O-rings which will leak even with fresh O-rings.  If this is 
the case you probably have rust in the cylinder bore as well and a complete 
rebuild is in order.

I have had mixed results rebuilding cylinders and when I consider how 
important brakes are I usually opt for a professional rebuild or a brand new 
master 
cylinder.  A new MC retails for $200 but if you shop the sales you can pick one 
up for less.

I would suggest you buy a rebuild kit and pull the cylinder.  Remove the 
reservoir and check for rust in the recesses.  If you find no rust and age 
hardened O-rings then replace the O-rings.  Check for fluid leakage into the 
booster. 
 If the cups leak you may not see fluid because it will get drawn into the 
booster where the brake fluid will weaken the diaghram and cause the booster to 
fail.  (BTDT)  If you find fluid the cylinder needs rebuilding.

Remember, this car is 32 years old and these types of problems are par for 
the course in any car this old.

If your brakes are all original I would go so far as to recommend a new 
master cylinder, new wheel cylinders and caliper rebuilds as well as four new 
brake 
hoses.  Do a visual inspection of all the steel lines for deep rust pitting.  
If your car is relatively free of rust odds are the brake lines are, too.  
Throw in new pads and shoes and turn your drums and rotors and you will have a 
brand new braking system.  It will cost less than $400 in parts.  Since your 
brakes are still working you can plan out this expense but I would certainly 
start saving/accumulating parts.

And your life may depend on it.  I still vividly recall the day the brakes 
failed on my MG.  And that was over 30 years ago.  Don't scrimp on brakes.

Dave


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