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Cat Man
Cat Man, Cat Engine Expert
Category: Boat
Satisfied Customers: 8910
Experience:  23 years Caterpillar Engine Experience
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I have Cat 3208s in my Grand Banks and have one engine that

Customer Question

I have Cat 3208s in my Grand Banks and have one engine that overflows the coolant overflow tank when I go to full power. It's OK at normal cruising speed (1800-2000 RPM). The engine doesn't overheat during the short time I have it at high power before the tank overflows - about five minutes. The coolant was tested and is good and has no sea water in it. Can you tell me what's causing this?
Submitted: 2 years ago.
Category: Boat
Expert:  Cat Man replied 2 years ago.
Hi. Thanks for asking your question! I will try and help you out.
There are two things I have seen cause coolant to overflow the tank.
The first is a bad radiator cap. Which you have already replaced.
Second is a blown head gasket at one of the cylinders. When this happens compression from the cylinder will pressurize the cooling system and cause coolant to be pushed out.
It's possible to have a cracked cylinder head but that is very rare.
I am sorry. I wish I had better news.
Please reply back if you need more help or have more questions. I am happy to assist.
Expert:  Cat Man replied 2 years ago.
Hey. I just wanted to see how things were going. Please let me know if you need more help. I am happy to assist. If my information was helpful, please leave a good or higher rating so that I receive credit. Thanks!