coolant water level on Yanmar yr 2000 6LP-STE

[Russell]

I must be missing something here but I do not understand why you are looking for a leak. You did not mention that it overheats. When the engine is hot the coolant expands and fills the overflow bottle. As it cools down the overflow goes back into the engine. If anything it sounds like it may have been overfilled. I am not familiar with the Yanmar engine but does it have an alarm for coolant overfill?

[peterf]

It has an alarm for low level. I have checked at idle & cruise 3 times and same problem. Have had to refill engine coolant tank 3 times at about 2/3 of a gallon ea., time. Have checked for leak on all hoses around coolant tank, aftercooler, hot water tank etc etc. Can't find a #@**$# leak so now will try a pressure test

[peterf]

Also don't understand why when the coolant is low why would the overfill bottle be full?? Doesn't make sense to me. Engine temp at cruise is 174 to 176

[mike66]

Def need that pressure test. All heat exchangers are capable of leaking over time..wear items although expensive. Your expansion tank would fill while the level is high and the coolant gets hot; it would stay up as long as your system has pressure. Eventually if you lost enough coolant it might come down but maybe not until the engine cools.

[RobS]

Aftercooler does not see coolant, the only part of the raw water side that sees coolant is the heat-x.

[peterf]

there is coolant in the bilge coming from somewhere

[mike66]

If you can pressurize the system with a tester the source should be easier to find. There is fluorescent dye available to make the leak easier to find.

[RobS]

It does sound like you have eliminated an internal leak within the heat-x or the domestic water heater. Check the two 5/8" heater hoses that run from the engine to the water heater. Also check the coolant drain cocks on the engine, one is on the engine block and the other is on the heat ex.

[Tree]

I'll second what Rob has pointed out there. I replaced mine earlier this year due to dry rot. There is a lot of hose there that could potentially fail at any given point when it is at that stage of degradation.

[peterf]

Well to continue with the saga I went out with a mechanic and he found when he held up the expansion overfill hose it would spew out coolant like a fire hose then stop for awhile then start again. I must have checked when it had stopped. Will be pressure testing soon and he thinks it could be a pinhole or the head gasket. I hope it's a pinhole

[peterf]

Well finally an end to this saga I hope! After all the testing for leaks everywhere We finally found the problem. When the problem first started a few days ago the first thing I did was change the the coolant pressure cap to a new one. After being frustrated I called my local mechanic and he looked over and could't find any hose or fitting leaks. we then decided that we would test at cruise and after about 15 or 20 mins as he was looking at the overfill tube it started to spew like a fire hose and then would stop for awhile and start all over again. I must have checked it when it had stopped.Came back, pressure tested the coolant and found it was dumping coolant as 10 psi instead the rated 13 psi. Changed to another Yanmar spare pressure cap and problem solved!!
Even though I am 73 I keep learning new things every day

Thanks to all for your excellent suggestions that helped me go through the process.
Peter

[Pitou]

That's a nice fix!