I have a uneversal M 18 in my boat approx 700 hours.I noticed it was running a little hot, thought it be airbound. While tied to my mooring let the engine come to temp while under load. I losen the valve on top of thermostse got a little hiss of air, did this a couple of times then forgot what position the valve was in. Ended up screwing all the way in. The next time out I overheated,then let the engine cool down added antifreeze then left valve in the open posistion, boat was fine for a couple of trips, tonight I happen to check and antifrezze and it was almost all gone. No sighn of anything lesking nothing in blige, where could it have gone?
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The Case of the Missing Coolant
I had a similar problem and when I ran the engine the coolant was replaced by salt water. The heat exchanger was bad and leaking internally and mixing the 2 'sides' of the cooling system. I pulled the old heat exchanger, flushed the system with fresh water and installed a new heat exchanger. Life is good and cool again.
I had a similar problem and when I ran the engine the coolant was replaced by salt water. The heat exchanger was bad and leaking internally and mixing the 2 'sides' of the cooling system. I pulled the old heat exchanger, flushed the system with fresh water and installed a new heat exchanger. Life is good and cool again.
Another possibility
Is that your heat exchanger is not leaking, but your engine is consuming it (vaporizing it and spitting it outt he exhaust)
Is that your heat exchanger is not leaking, but your engine is consuming it (vaporizing it and spitting it outt he exhaust)
Possibilities ....
1. Leaking gasket on 'radiator cap' ..... what's the status of your overflow tank? gaining water level? 2. Leaking shaft seal on water pump .... check the crankcase for 'muddy' looking lube oil or an INCREASE in the lube oil content .... check the level on the 'dipstick' 3. Blown/leaking head gasket. A knowledgeable mechanic will be able to tell by putting a fluorescing chemical into the cooling water and after t he engine is run for several hours, come back with a 'black light' and see if there is a high concentration of CO or CO2 in the cooling water. He can also do a combustion chamber 'leak down test' with high pressure air being injected into the fuel injector ports. 4. Heat exchanger leak from fresh water side to raw water side (pinhole) 5. Pin hole leak in *potable hot water heater coil* ... that could be serious if you are using it in food preparation, etc. Do you have your *potable fresh water pump* cycling on/off 'mysteriously' every once in a while?
1. Leaking gasket on 'radiator cap' ..... what's the status of your overflow tank? gaining water level? 2. Leaking shaft seal on water pump .... check the crankcase for 'muddy' looking lube oil or an INCREASE in the lube oil content .... check the level on the 'dipstick' 3. Blown/leaking head gasket. A knowledgeable mechanic will be able to tell by putting a fluorescing chemical into the cooling water and after t he engine is run for several hours, come back with a 'black light' and see if there is a high concentration of CO or CO2 in the cooling water. He can also do a combustion chamber 'leak down test' with high pressure air being injected into the fuel injector ports. 4. Heat exchanger leak from fresh water side to raw water side (pinhole) 5. Pin hole leak in *potable hot water heater coil* ... that could be serious if you are using it in food preparation, etc. Do you have your *potable fresh water pump* cycling on/off 'mysteriously' every once in a while?
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