At 09:54 AM 7/20/2000 -0400, Bill Saidel wrote:
>....
>If you don't mind my pursuing this a bit, the first 2 times it overflowed,
the fluid was just that, fluid. It was only the last time that the fluid
was foamy.
>
>If it is the head gasket, what other symptoms might I expect to experience?
With only a small head gasket leak the symptoms may be nearly indetectable,
except for some occasional coolant loss. To be sure if you're losing
coolant, install a transparent recovery tank (and a coolant recovery type
radiator cap) and watch the rise and fall with temperature changes. If you
have to add fluid to maintain the level you have a leak.
With even a small head gasket leak, if you run the engine hard for a
prolonged period it will blow the coolant out past the pressure cap. If
you have a coolant recovery tank it will also percolate bubbles into the
tank rather than just liquid, especially during the first few minutes just
after you shut the engine off.
If you suspect a leak anywhere in the cooling system, have it pressure
tested. The standard test tool is a small hand pump and pressure gauge
that fits on the radiator in place of the pressure cap. Fill the radiator
to the top with coolant before applying pressure, less air the better.
Pump up 10 psi and watch the gauge. The pressure may drop 1 or 2 psi in
the first minute as the hoses expand a bit, and than stabilize. Pump it
back up to 10 psi and let it set for several minutes. If the pressure
drops quickly there WILL be coolant running out somewhere. If it isn't
running out on the ground it is running inside the engine, into a cylinder
or into the oil sump. External leaks are easy to spot. Internal leaks are
real hair raisers, usually a head gasket, occasionally a cracked head, and
only very rarely a cracked block.
It is possible to have a leaky head gasket (into the cooling system) and
not have it show up with a cooling system pressure test. I once had this
problem where the presure test showed a perfectly tight cooling system, but
when the engine was run hot and hard the compression gasses would blow past
the head gasket and blow the coolant out past the pressure cap. The head
gasket was acting like a check valve where the pressure in the cooling
system would not blow past the gasket, but the higher pressure of
combustion would. With the pressure tester in place and the engine
running, when I blipped the throttle hard the coolant pressure would junp
up a couple psi and stay there. Another blip on the throttle would push it
up a couple more psi.
Do let us know what you find.
Barney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg
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