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Oveflowing coolant reservoir

Kevinde

New member
I have a 1974 318 FWC engine with a coolant reservoir that overflows everytime I run the engine. I have put an empty juice on the overflow hose to catch the coolant and reuse it, but a day long usage will run the reservoir dry. The coolant is clean and not discolored by oil, exhaust, or rust. I have tried a few new caps with no success. I don't know that it matters, but this engine also has the hoses sending coolant to the cabin air heat exchanger.
 
Check your heat exchanger for internal leaks. Maybe its leaking sea water into your coolant, thus increasing the fluid level and creating the overflow.

-JJ
 
I don't think think the raw water side operates at a higher pressure than the fresh water side, but I guess it could. I also have two year old exhaust manifolds and boiled out and checked the heat exchanger at the same time. They run fluid pretty freely now.

I'm thinking I could have a stuck thermostat and fluid from the cabin heat exchanger is overfilling things before it can open. I'll check that first. Maybe rerouting lines is in order, or finding a thermostat for the heat hoses.
 
You might also try a pressure tester (borrowed from Auto Zone) to see if you have any leaks.

Sorry to say it, but you might have a head gasket going--that would cause that. If the pressure won't hold with the tester, pull the plugs, wheel her over, and look for coolant coming out. (You'll need a couple of sharp-eyed helpers for that.)

Hope that's NOT it.

Jeff
 
I don't think think the raw water side operates at a higher pressure than the fresh water side, but I guess it could.

It could if your fresh water side was no longer a closed system (a.k.a internal leak). Keep in mind that the fresh water side operates under pressure due to heat in a closed volume. If that volume is now open due to a leak, you'll lose pressure in the system.

-JJ
 
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