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Re: Head leak

To: Danny Varnado <>, mgs@Autox.Team.Net
Subject: Re: Head leak
From: Rocky Frisco <>
Date: Thu, 21 Oct 2004 22:23:16 -0500
Danny Varnado wrote:

> List,
>> I have a very strange water leak problem on my '74 MGB engine.  After 
>> driving about 10 miles a small white dried run of water (antifreeze 
>> residue) will appear.  It shows up on the spark plug side of the head 
>> about 3/8" from the top of the head above and towards the front of #3 
>> spark plug. I have cleaned off the paint and wire brushed the area .  
>> I have looked at the area with a magnifying glass and had it dye 
>> checked to look for a crack or pin hole.  I have inspected the area  
>> cold, hot, and hot with the engine running without finding any 
>> indication of the leak.  I have never seen the leak wet, only the 
>> dried residue of the run after driving the car.   It's almost like 
>> water loss through osmosis.  The amount of water leaking is almost 
>> insignificant.  I cannot detect any drop in the overflow tank level. 
>> My concern is whether or not the head has a very thin spot in the 
>> water jacket because of poor casting, corrosion or erosion.  I don't 
>> know wether or not it will get any worse  I'd hate to be going down 
>> the road and have it blow out.  Any suggestions would be greatly 
>> appreciated.

Might not be coming from inside the head. Might be a pinhole leak in a 
hose that only happens when it's fully hot. I would treat it like a 
detective story: thoroughly clean the area again, make sure it's dry, 
then, using duct tape or masking tape, affix a piece of white paper 
over the area where you see the residue. If the residue is white, use 
dark paper. Take a run or two. You should then be able to see where 
the residue is coming from, a leak or a squirt, or droplets in a 

If you do find an "osmotic" leak, I would be satisfied, myself, with a 
coin epoxied over the area with really good industrial epoxy, not the 
fast-set stuff.

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