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.
1958 MGA with an attitude
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