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coolant loss troubleshooting recommendations?

5K views 38 replies 12 participants last post by  sailingdog 
#1 ·
hi, it seems like after i run my engine for a while (a couple hours) the next day i have to top the radiator up w/ coolant (2-3 cups full). i don't think this is normal (?) and i m kind of lost at where to start in order to check it out. i think this is a relatively recent problem, as the boat did not seem to require coolant on its long delivery (13 days), but it seems to start after i had the engine 'fixed' for an oil leak at the local yard. nothing obvious as far as why/ where the loss is coming from. btw its a 10 yr old diesel w/ both a fresh water cooler and a raw water cooler. thanks for any thoughts. cheers
 
#31 ·
If you can't see or smell the coolant and the oil doesn't look like a milkshake, the coolant is either being lost in the heat exchanger or it's being evaporated in a cylinder. Before you get out your wallet, it's time to have a conversation with the people that disturbed your head gasket during the prior service. You can sniff the coolant tank for hydrocarbons when the engine is at operating temps, but you'll need to find someone with a portable gas analyzer to do it.
 
#32 ·
resdog said:
If you can't see or smell the coolant and the oil doesn't look like a milkshake, the coolant is either being lost in the heat exchanger or it's being evaporated in a cylinder. Before you get out your wallet, it's time to have a conversation with the people that disturbed your head gasket during the prior service. You can sniff the coolant tank for hydrocarbons when the engine is at operating temps, but you'll need to find someone with a portable gas analyzer to do it.
yep i agree. i m guessing its something in the heat exchanger cuz it seems that if it was a cylinder head problem, if you take the radiator cover off it should bubble or gurgle over, and mine doesnt do that...
 
#34 ·
pigslo said:
One last thought on this in regard to diesels. The compression ratio is so high that any water in the cylinder will blow the head off when it turns to steam upon combustion. That is why the filter separates the water from the fuel.
thats a pleasant thought! well i guess that may mean that it can't be water in the head cuz its hasnt blown off yet?
 
#35 ·
In the case I have seen, the 4-stroke cylinder on the combustion stroke was blowing gas past the gasket and a water channel. In the process a little water was vapourized and ejected. It only happened at running speed and the exit point was well hidden under the exhaust manifold, so it took an age to detect.
At running speed, the cooling assembly was slightly pressurised and a little above normal boiling point, so taking the radiator cap off was not that advisable. It was a vehicle not a boat engine.
Only speculation: in your case, if the gas is blown by a compression stroke cylinder, past the water channel, into an exhaust stroke cylinder, the water would apparently vanish entirely.
 
#38 ·
hi, i 'think' its resolved. i ended up taking off the cylinder heads and having them resurfaced and putting them back together. my guess is that when the boat engine over heated following the 'repair', the heads warped and thats when the leak appeared. anyway, i ve run it for the past 3 weekends and the coolant level is stable so i m hoping that was it! thanks everyone for their thoughts
 
#39 ·
Either that or you blew the head gasket someplace.
 
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