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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
 
#3 ·
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.
 
#4 ·
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
 
#5 ·
Stay Cool

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!
 
#6 ·
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.
 
#7 ·
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.:confused:
 
#10 ·
mrkeith said:
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.
 
#12 ·
mr kieth...OK...assuming you are not getting any in the bilge and there are no visible leaks anywhere (you did check that water pump right?)....There are no outlets for the green stuff except your exhaust system or your crankcase.
Pigslo is right that the heat exchanger and the oil cooler (if you have one) are the only places that you can lose green stuff to the exhaust. To check these, each must be removed and pressure tested if visible inspection reveals nothing.
The easiest first step though is changing your oil to be double sure it is not getting into your oil system first...since you will probably want an oil change to start the season anyway.
Eliminating this possibility leaves you with only the exchangers as possibilities and I would start with the heat exchanger as most tranny oil coolers use fresh water rather than the sealed system for cooling.
Edit: Re-reading your last post...what temperature are you seeing on your guage when you run at 2000 or is it just an "idiot light"?
Good luck and let us know what you find.
 
#13 ·
Cam-

I think you mean that tranny oil coolers use raw water, rather than the sealed system for cooling. Fresh water is a term that is a bit confusing when it comes to sailboat engines and their cooling systems. ;)
 
#14 ·
Sounds not good then. If the head was off to fix an oil leak, it may now have created a water leak. The coolant has to pass from head to block the same as the oil (via a different bore of course) and back again. I have had an engine that lost water steadily. It was all being sucked into one cylinder and blown out as steam. Not easy to detect from external signs. The big snag is that the water may accumulate in the cylinder while stationary for a long period and that could turn very nasty - both from a corrosion and an (in)compression point of view. I suggest you alert the shop that did the maintenance. If they are responsible people, they will at least come and check.
 
#15 ·
I rebuilt engines in my GTOs as a "child" growing up in Houston so I thought my 4-108 would be easy. Jaysus! Diesels are complicated most in the water and oil cooling system. I took digital pictures and made notes as to the path and purpose of each hose. You don't need to rebuild your engine to understand it but tracing all the hoses would make you a bit more self sufficient. Check your tranny fluid while you are at it.
pigslo
 
#17 ·
camaraderie said:
mr kieth...OK...assuming you are not getting any in the bilge and there are no visible leaks anywhere (you did check that water pump right?)....There are no outlets for the green stuff except your exhaust system or your crankcase.
Pigslo is right that the heat exchanger and the oil cooler (if you have one) are the only places that you can lose green stuff to the exhaust. To check these, each must be removed and pressure tested if visible inspection reveals nothing.
The easiest first step though is changing your oil to be double sure it is not getting into your oil system first...since you will probably want an oil change to start the season anyway.
Eliminating this possibility leaves you with only the exchangers as possibilities and I would start with the heat exchanger as most tranny oil coolers use fresh water rather than the sealed system for cooling.
Edit: Re-reading your last post...what temperature are you seeing on your guage when you run at 2000 or is it just an "idiot light"?
Good luck and let us know what you find.
temp is about 150 to 160 and oil pressure is around 40-60
 
#18 ·
if i just keep using it while i am trying to figure out the problem, while making sure the coolant level is full up, is that a problem? i guess realistically this could be as simple as the radiator cap isnt completely sealed (although it appears to be) to the coolant is being sucked somewhere into the engine. it if when to the oil, wouldnt the oil be looking a bit green?
 
#20 ·
pigslo said:
Not trying to be curt, but hard to say since we don't know the cause. Damage range.... nothing to rusted cylinder walls. Keep looking, you will find it
pigslo
thank you. i was told maybe that the cylinder head gasket maybe be bad and that to test this you take of the radiator cap, rev the engine, and if coolant spills over it means the gasket is bad. does that make sense?
 
#21 ·
Actually that is kinda cool for most diesels so it doesn't seem like there is any overheating issue. Based on the fact that you are not losing any fluid at the dock...it may be an underway issue with the engine under load. Given Pigslos comments I am leaning to the tranny oil cooler now.
I would definitely pull some fluid out of your tranny and check it for contamination.
As to damage... I would like to tell you to leave the dock and motor a while but if that sucks coolant into your tranny or engine block you could have big problems. Again...I would change the oil inspect it and inspect the tranny fluid. If there is no evidence of contamination in either...I would then take the boat for a run under power and see if fluid levels go down. If they do...check oil and tranny again and if there is no contamination it is almost certainly one of your exchangers.
 
#22 ·
ok thanks. the oil doesnt look 'greenish'. i havent checked the transmission fluid except a quick glance the other day to see if it was topped off. again i don't remember anything green. the heat exchanger we took out a little while ago and there wasnt anything 'noticeable'. i guess if its the heat exchanger that just means coolant is leaking out into the raw water system and being flushed out?
 
#23 ·
You said you had the cylinder head gasket replaced?
My thought would be that this is where you issue is.
Instead of leaking externally as it was it is now leaking a very small amount of collant water into a cylinder, but only under load.

You might try simply torquing the cylinder head bolts down to spec. Perhaps they were not tightened properly.

Beyond that it would really be something that one would have to see.

Good luck!

Todd
 
#25 ·
Certain head gaskets still need a second torqueing after a certain amount of hours. Many newer ones are torqued once at installation. Nevertheless I think you will find your problem in that area, as it was worked on most recently. Was the head checked for warpage when the gaskets were done? Your local auto mechanic will probably have a tester that samples your coolant for hydrocarbons. As previously stated, the oil pressure is much higher than coolant pressure and so the oil will show up in the coolant first. Check around with a few mechanics. I think you need to sample the coolant hot-ask the mechanic with the tester.
I am also in agreement that your engine is running a little cold. 180 degrees is generally considered the point at which your most efficient combustion and, more importantly, you begin to burn out moisture and impurities from the engine's lubricating system. A cold running engine also hastens the demise of everything down stream from the exhaust manifold.
Good luck. I'm bettin' on the head.
 
#26 ·
camaraderie said:
Actually that is kinda cool for most diesels so it doesn't seem like there is any overheating issue. Based on the fact that you are not losing any fluid at the dock...it may be an underway issue with the engine under load. Given Pigslos comments I am leaning to the tranny oil cooler now.
I would definitely pull some fluid out of your tranny and check it for contamination.
As to damage... I would like to tell you to leave the dock and motor a while but if that sucks coolant into your tranny or engine block you could have big problems. Again...I would change the oil inspect it and inspect the tranny fluid. If there is no evidence of contamination in either...I would then take the boat for a run under power and see if fluid levels go down. If they do...check oil and tranny again and if there is no contamination it is almost certainly one of your exchangers.
well i m still w/o a solution, both tranny and oil fluids a fine, and no white smoke out the back. cylinder head is torched up. hoses seem tight and no tell tale green drip. i replaced the radiator cap but i m not sure thats going to result in anything............i guess i need to take the heat exchanger out and get it tested again?
 
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