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Old 23-08-2016, 05:53   #1
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Engine Expansion Tank overfilling - Solved!

A couple of months ago I had an issue with my Westerbeke's expansion tank filling to the brim. I then replaced the 14 year old heat exchanger believing there was an internal leak with raw water leaking into the coolant circuit (when the engine was at operating temperature).

That didn't solve the expansion tank from filling. The only other area that raw and coolant comes into close contact was the hot water heater. Since the Force heater was 14 yrs old I replaced it, too. That solved the problem.

I never noticed the hot water having any sign of antifreeze in it when washing but advise not making tea with it!

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Old 23-08-2016, 06:34   #2
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Re: Engine Expansion Tank overfilling - Solved!

With out knowing all the details I would think possible head gasket leak pressurizing the cooling system causing the coolant to get forced into the overflow tank.
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Old 23-08-2016, 06:47   #3
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Re: Engine Expansion Tank overfilling - Solved!

A bad head gasket would be a possible cause but in this case it wasn't. There were no bubbles in the tank and head gaskets don't mend themselves. The tank remains 1/2 filled months later.

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Old 23-08-2016, 07:39   #4
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Re: Engine Expansion Tank overfilling - Solved!

I had the same issue. The pressure of the hot water heater is higher than the engine coolant pressure, so if there is a leak in the water heat exchanger, water is forced into the engine.

It is possible to get antifreeze into your hot water, but only if the engine is run (and coolant pressured up) when the freshwater pump is shut off.
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Old 23-08-2016, 08:03   #5
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Re: Engine Expansion Tank overfilling - Solved!

Quote:
Originally Posted by ronbo1 View Post
A bad head gasket would be a possible cause but in this case it wasn't. There were no bubbles in the tank and head gaskets don't mend themselves. The tank remains 1/2 filled months later.

Ronbo

From my automotive background, I would have first thought headgasket myself, I would likely have never considered the water heater, I'll have to try to remember this as I would have been pulling my hair out and would likely have thought great, I have a cracked head when the gasket didn't fix it.
Why do we call them hot water heaters, when they are actually cold water heaters ?
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Old 24-08-2016, 08:03   #6
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Re: Engine Expansion Tank overfilling - Solved!

It is unusual for the heat exchanger in the water heater to leak, Usually, the tank fails first.
On some heaters, the exchanger is a double wall arrangement, vented to atmosphere. While the domestic water is a higher pressure, there is always a possibility of contamination. AND the water in the water heater usually doesnt taste as good. Cook with Cold water, drink cold water. My mate avoids tank water.
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