Matt, I had similar symptoms a few years ago, with some variations; I'm
crossing my fingers that this is not your problem.
I don't drive my 67.5 1600 over 4000 revs normally, mine did some coolant
loss out of the overflow while running & I believe normally lost some after
stopping; it consistently kept losing coolant with no oil contamination.
Turned out I had some cracks in the head between the cylinders & the water
passages (with about 250K+ on the car, yes the engine's been overhauled
twice). The result was that it would suck coolant on the intake stroke,
and blow coolant out of the resevoir on the compression & firing stroke.
If you have any thought that this may be happening, the only way to test
is to have a good head shop do a "leak-down test". Quality shops can do
this to a head you pull off the car, I believe they can also do this
with the engine intact; either one requires you to drop the car or head
off overnight.
This test will also show head gasket problems, if the gasket leaks between
a water passage & the cylinder--but the oil passages are OK--it'll give
the same symptoms, with the added problem that sucking water into the
chamber on the intake stroke will cause the aluminum head to erode rapidly
on firing; this may have been the cause of my head developing cracks, and
the head was quite interestingly deformed from erosion.
Good luck--as I said, I'm hoping this isn't what's up with your car.
Tom Stockman
ftuck@frii.com
Morrison CO
67.5 1600, 300K+
> Since I have not had any problems until recently, I have not paid a lot of
>attention to the previous emails about cooling system problems. Just recently
>(within the last 2 weeks) I have started having a problem with my cooling
>system. Symptoms are as follows:
>
> Car runs fine at normal operating temperature no matter what the driving
>conditions are, only rising when coolant is low.
> Ambient temperature ranges from 75-100 degrees.
> While car is running, I have no coolant leaks.
> With radiator cap (thermostat housing) off, I can see the coolant flowing
>once the car warms up.
> After turning the car off, my car pukes out through the overflow/reservoir
>loosing about one cup or more of coolant each time (seems to be only after
>being driven hard at higher rpms - 4500+).
> I have compression tested all cylinders. Compression is even across and
>there was no bleed down on any of the cylinders (leading me to believe my head
>gasket is ok).
> The oil is clean with no signs of coolant.
>
> I am lost. Help please....
>
> Matt
> '70 1600
>
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