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Coolant flowing out of reservoir

H

hmeloche

New member
I have a 1988 Mercruiser 3.7L I/O, 4 cylinder, with closed coolant system and a heat exchanger using lake water to cool the coolant. First time out this year I noticed coolant in the plastic reservoir went from half full to overflowing. A lot of coolant came out of the overflow hole in the plastic cap on the reservoir.

I noticed the coolant metal cap at the top of the engine (looks and works like a radiator cap) was not tight and thought that might fix it, but it did not. Any ideas on why quarts of coolant would over flow out of the reservoir?
 
A failing head gasket that is leaking off cylinder pressure may pressurize the cooling system, and may cause what you are seeing.

You can purchase test strips that will indicate the presence of hydrocarbons in the coolant.


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My impeller (water pump) was fried. I am not sure why. It was 2 years old and I never run without water. Had it fixed and is running great. I was worried it was the heat exchanger particularly after this brutal winter. Ran for about an hour on Lake Huron. Thanks for your help.
H
 
hmeloche said:
My impeller (water pump) was fried. I am not sure why. It was 2 years old and I never run without water. Had it fixed and is running great. I was worried it was the heat exchanger particularly after this brutal winter. Ran for about an hour on Lake Huron. Thanks for your help.
H
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A "soft grounding" or "kissing" a sand or gravel bank can take out your impeller quite quickly, which I why I converted to thru hull pickup given that my home waters are Barnegat (I know there's deep enough water somewhere around here!... it was here last week!!) Bay/Inlet.
 
And I am getting coolant in the bilge again. Have not had a chance to watch it this time, but probably coming from the reservoir. I am now starting to believe I have a bad heat exchanger as well. The engine is not overheating and there is no reduction in the coolant level, making me think that the lake water is somehow getting mixed with the coolant. I never see green coming out of the outdrive, however, leaving me a bit confused.
 
hmeloche said:
And I am getting coolant in the bilge again. Have not had a chance to watch it this time, but probably coming from the reservoir. I am now starting to believe I have a bad heat exchanger as well. The engine is not overheating and there is no reduction in the coolant level, making me think that the lake water is somehow getting mixed with the coolant. I never see green coming out of the outdrive, however, leaving me a bit confused.
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Sorry my friend, I was surprised that impeller was causing an overflow and NOT overheating…. My money is still on the H.E. It makes perfect sense. Simple to replace, as I mentioned before Seakamp makes direct replacements. I got mine from "Partman" in New York.
Best of luck
Rick
 
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