Chrysler LM318 - Fresh water cooled - No coolant in the tank

[TBarCYa]

I hear big problems with my LM318. When I brought the boat 60 miles up the river to bring it home for the winter, I had absolutely no problems with the cooling system and the temp gauge stayed in the normal range the entire trip. Today, I was winterizing the engine and when I took the "radiator" cap off, I found that the tank that sits on top of the engine is empty. We had two nights in the 30s but there was a 50/50 mix in the cooling system prior to this. A quick look doesn't reveal any physical damage to the engine, but I fear this is pointing to a big problem. Any idea where I should look? I didn't see coolant in the bilge, there's obviously very little in the cooling system and other than going out the exhaust, there's nowhere I can figure it would have gone. Any ideas? Anecdotal stories?

Thanks in advance.

 

[TBarCYa]

More information... I checked the oil and it's clean and free of water. I pulled the hose from the tank to the heat exchanger and there is coolant in the heat exchanger. I also pulled one of the block drain plugs and there's coolant there too. The winter will be spent buying cooling system hoses and I'll be replacing all of them before spring but I'm still curious where the coolant might have gone. She spent 3 months in the water and it wasn't until after she was hauled for the season that she lost coolant.

 

[Scott Danforth]

post a picture of the heat exchanger. you may simply need to add a surge tank (aka puke tank) to ensure you have enough expansion / draw down volume.

also, it may be a good idea to take the HX's off to a radiator shop for pressure testing to make sure everything is golden for spring.

 

[TBarCYa]

If by a "surge tank" you mean something like the "overflow tank" in a car, I have one of those. I also have a tank on top of the engine that has the "radiator cap" which is the tank that's empty. I'll take some pics of what I have so you have a better idea.

 

[Bondo]

If by a "surge tank" you mean something like the "overflow tank" in a car, I have one of those. I also have a tank on top of the engine that has the "radiator cap" which is the tank that's empty. I'll take some pics of what I have so you have a better idea.

Ayuh,.... So fill it up,.....or at least fill it within a inch or two of the top,...

 

[TBarCYa]

I'm ok with filling it up, but a little concerned where the coolant that I put in it could have gone.

While on the subject of cooling systems, any idea how to go about finding the replacement hoses? The one from the tank to the heat exchanger is a molded hose (pre bent rubber hose) and I imagine it's not exactly generic.

 

[Bondo]

I'm ok with filling it up, but a little concerned where the coolant that I put in it could have gone.

While on the subject of cooling systems, any idea how to go about finding the replacement hoses? The one from the tank to the heat exchanger is a molded hose (pre bent rubber hose) and I imagine it's not exactly generic.

Ayuh,.... For molded hoses, ya gotta track down the manufacturer of the coolin' system, 'n use their parts systems, or search their part numbers in the aftermarket,...

To find yer coolant leak, use an automotive pressure tester,...it screws on where the cap is,... mine is a Stant,...

Basically, drain the system, hook up the pump, 'n pressurize,....
You'll hear the leak, follow the sound,...