coolant overflow or leak?

[spec2]

I have a Volvo Penta MD 2020. Have coolant spotting in the engine compartment. No evidence of leaking from the engine. Appears to be coming from the overflow tube running from the reservoir. I continually have to add coolant to top off and of course it over flows back out. Engine runs fine. approx 375 hours. There is no temp gauge on my boat. No alarms are sounding or temp lights on. No smoke out of the exhaust. Any thoughts?

[jrd22]

Could be a leaking head gasket allowing exhaust gas to enter the cooling system. Try leaving the cap to the overflow reservoir a little loose to see if that stops the overflowing, or test the coolant for exhaust (I think you can buy a test kit at an auto or truck parts store).

[MARC2012]

It should not be full(expansion tank),could be your problem?marc

[spec2]

thanks for the advice. I'll look to buy a test kit. Marc..Re your comment, it should not be full. How much coolant should be in the reservoir? Clearly its not overfilled, but I can see the coolant when opening the cap. I assume the reservoir should not be dry?

[christyleigh]

There should be lines and verbage on the reservoir similar to a dipstick - low and full. Full on mine is only about 2/3 of the way up. Mine is hard to see and actually I also have a little coolant dripping into the engine bilge area that has me a little concerned.

[MitchM]

if you are losing that much coolant i'd suspect (1) a leak in in your freshwater antifreeze coolant lines, pinhole leak or crack ? (2) a leaky seal in your freshwater a/f coolant pump (look for d rips under the pup by fitting a cloth 'diaper' under the pump or (3) a leak where your engine a/f hoses circulate thru a hot water heater . common for those hw htr hoses to chafe or abrade on a bulkhead and blow coolant into the engine compartment or h w htr compartment , which leaks can be a devil to find.

get ahold of a stant pressure tester , you'll need a cap to fit the volvo radiator cap- take the cap with you and see if your local autoparts store will rent you a stant. then you can pressurize your a/f system using the stant installed in the radiator cap, pressure the stant to about 7 psi and you should see a stream of a/f shooting out some where. then you have to fix it... if you dont find this coolant leak you run the risk of an engine overheat and that wont be pretty.

let us know what you find. if you're anywhere near erie pa i'll lend you my stant.

[JiffyLube]

Another thing that can raise the coolant level would be a leak on the raw water side of the heat exchanger, leaking raw water into the coolant side raising the level to overflow...happened to me once.