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Re: Cooliong question and thanks

To: Phil <>,
Subject: Re: Cooliong question and thanks
From: Barney Gaylord <>
Date: Mon, 02 Sep 2002 17:11:23 -0500
At 02:45 PM 9/2/02 -0600, Phil Bates wrote:
>.... I seem to be doing a lot of overflowing on the coolant.  Not 
>overheating, but it is overflowing.  I usually add about a quart of water 
>every 3 or 4 days and I know that is too much.

Have you measured the exact amount of coolant you are putting back into the 
radiator?  If you fill it to the top it will blow some coolant out when it 
warms up.  Thermal expansion of the coolant will force out about one pint 
of coolant between a cold start and full running temperature.  After 
shutdown, when it cools off completely the coolant contracts and will leave 
the one pint of air space in the top tank of the ratiator.

>It doesn't appear to be burning it (and I replaced the head gasket about 2 
>years ago due to similar concerns), and my radiator cap (a safety cap) is 
>fairly new.  I also have a new radiator (from moss from china) within the 
>last year and a new water pump a couple years ago.

You should do a  pressure test on the cooling system.  If you don't have 
the tool, any radiator shop can do this for you in a few minutes.  The 
pressure tester is a small hand pump with a pressure gauge and an 
attachment fitting similar in form to a radiator cap.  You fill the system 
to the top with liquid, no air.  Then attach the tester and pump up about 
10 psi of pressure, and wait a minute to see if it holds the pressure.  If 
the pressure goes down you go looking to see where the coolant is 
going.  Most likely you would find it leaking out the front of the water 
pump, or through a pinhole or split seam in the radiator, or at a loose 
hose clamp.  If it is not running out on the ground it is likely going into 
the oil sump, not a pleasant thought, but also not many other possibilities 
for a hidden leak, and probably caused by a bad head gasket.

I had one case some years ago where the initial pressure test was perfect, 
but the car would spit out coolant when running on the highway while it was 
not overheating.  This turned out to be a head gasket leak that would not 
leak with the low pressure of the test tool, but when run hard with a heavy 
throttle the combustion pressure would leak past the head gasket into the 
water jacket adn blow the coolant out past the pressure cap.  The final 
discovery of that problem came with a pressure test while the engine was 
running.  At idle everything looked okay adn it held the pressure.  With a 
strong blip on the throttle the cooling system pressure would immediately 
jump up about 2 psi and stay there.  Another blip on the throttle would 
raise it another 2 psi, and it would never go back down.  In effect the 
head gasket was acting like a pressure relief check valve.  Maybe the head 
bolts weren't quite tight enough, or the head may have been not perfectly 
flat.  A new head gasket cured the problem.

>   I'm thinking about going back to my old water pump (looks like the 
> original pump from 1958) that had a metal rotor rather than the later one 
> that had plastic.

The original iron water pumps are pretty robust.  I have transfered mine 
from engine to engine a couple of times with engine rebuilds.  To the best 
of my knowledge it's the one that came on the car from the factory, and now 
has nearly 300,000 miles on it.  I did use an aftermarket aluminum bodied 
water pump for a while, but ultimately broke two of those where the 
generator attaches.  Appearantly the replacement aluminum model is about 
the same shape and thickness as the original iron one, but the aluminum is 
not a strong as the iron in the area of the generator mounting 
bracket.  Now I use only original iron water pumps, and am happy to accept 
a reject when someone is instaling a new aluminum one with an engine rebuild.

Barney Gaylord
1958 MGA with an attitude

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