coolant loss troubleshooting recommendations?

[mrkeith]

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

[RickBowman]

You are right it is not normal to be refilling your fresh water coolant system. Which model diesel is this? Do you have a fresh water coolant recovery tank? What was done to your diesel at the local yard? Is this vessel new to you as you mentioned a long delivery?

[camaraderie]

Does your engine oil look normal?
Is there any kind of sheen on the water near the exhaust when you run your engine at idle at the dock?
Do you have an engine temperature guage is is it reading in normal range when you are in gear at cruising speed?
How does the bilge look?
Are there engine/heat exchanger zincs and what shape are they in?

It is not normal to be losing coolant. Need answers to Rick's & my questions before we can offer some things to check.
I suspect a pinhole leak in your heat exchanger as the most likely culprit since you don't mention seeing any leaking and it is a common problem...but can't really pin it down without other answers.

[pigslo]

In a plain old car you would only check the oil for water, looks milky gray as it emulsifys. The ground around the car for a loose or broken hose. Or the floorboard foe a leaking heater core. A boat has two more places for the water to escape. It can leak from the heat exchanger into the overboard water as Cam suggests or it can leak at your engine oil /transmission oil cooler. In the case of the oil cooler the lost water coul end up in going into engine oil, transmission fluid, or overboard thru same path as heat exchanger. Based on the fact you had work done to fix an oil leak, I would take a close look at the oil cooler.
pigslo

[capngregg]

The responders are right on course with all their questions and things you need to investigate. Here are a few comments to consider and some information concerning some of their questions.

Does the engine compartment smell of coolant? This would indicate a leak somewhere on the engine or even the heat exchanger. During the oil leak repair I would not be surprised if the coolant hoses were removed at some point or maybe repositioned to some extent. Checking the tightness of all the clamps on the hoses as well as the condition of the hoses would be a basic starting point.

Often times the engine's water circulation pump seal and bushing will begin seeping, if it wasn't in great condition to begin with, and the drive belt was tightened. (possibly during the oil leak repair) There is a weep hole on the bottom of the circulation pump shaft that can be viewed to check the integrity of the pump seal. If there is coolant present there after the engine is brought to operating temperature then shut down, (don't try to inspect this area with the engine running!) this would indicate the seal is failing and will lead to coolant loss. This can lead to coolant consumption, eventual engine temperature issues and maybe even coolant leaked into the bilge area. You will also note that "hot engine smell" (evaporating coolant) when you access the engine compartment.

As for the "how does the oil look" comment, if there is coolant getting into the oil it will begin to look "frothy tan" around the fill point standpipe and in extreme cases your crankcase oil level will increase. This would indicate possibly a head gasket allowing coolant to migrate into the oil system. Since the pressure is higher in the cooling system (when the engine is at operating temp) than in the oil system, the coolant can migrate accross a corroded gasket and into the oil system.

As for the "sheen on the water" near the exhaust during operation at the slip, could indicate that coolant is passing into the exhaust system during engine operation. Not good either, and could also be a gasket issue or maybe a crack in the head.

I'd recommend starting with the simplest things first since the problem resulted immediately following a maintenance event but get the issue resolved before going too far from the slip. It won't heal itself and if left unattended may cause an unexpected and possibly very expensive failure.

Good Luck!

[Faster]

Typically if you have a head gasket problem white smoke is an indicator that you are burning antifreeze/coolant.

A boat's typical wet exhaust might hide this, but if you notice an enduring whitish smoke that wasn't there before, that would indicate a head gasket problem.

[mrkeith]

hi, some info,
the boat is new to me (6mths) and i helped deliver it from a distance about 2000 miles..i don't think we lost any coolant on the way back. this is a kubota engine that has been marinized, and it was in the yard getting a leaking head gasket oil seal replaced. they took the whole engine out and painted it at the time. temp gauge reads normal and the oil looks fine, maybe a bit darker than i would have thought given i had recently changed it.. there is no oily sheen on the water out the exhaust, and the smoke from the exhaust is a bit white but that seems to diminish after its been run for a while. i ran it yesterday for about 30 minutes and there was no noticable loss of water in radiator. what i am referring to is the fresh water cycle, not the raw water cycle. bilge is dry and since i am using anti freeze i would think that any leak would be highly noticable cuz of the green color of such. we took the heat exchanger off a while ago and tested it and the yard guys said there was no leak in it nor any leaks in the couplings holding the heat exchanger on . there are engine zincs but i havent checked them.

[pigslo]

The fresh water is conected to the raw water through the heat exchanger and the oil cooler.
pigslo

[mrkeith]

Originally Posted by pigslo

The fresh water is conected to the raw water through the heat exchanger and the oil cooler.
pigslo

hmmm what do i need to do to check if this is the problem? take everything apart?

[Idiens]

Originally Posted by mrkeith

i ran it yesterday for about 30 minutes and there was no noticable loss of water in radiator.

How many minutes have you run it altogether since the work was done on the engine? Do you have a calorifier attached to the engine (to heat tap water)?
It is possible that all that has happened is that air trapped in the calorifier, or elsewhere, has been now driven from the system and replaced by water, which you have had to top up.