Slow loss of antifreeze in Peninsular diesel

[Pedro]

I am not overheating but I have had a slow loss of coolant (no leaks) for three years of running, every once and awhile I'll check the tank and it's dry up to that first baffle,, half a gallon and i am good for several trips,,i installed an overflow tank but it must not develop enough pressure, to push out the excess and suck it back in,,
I'm guessing I need to have mechanic pressure test the loop? Internal leak in heat exchanger?,

[Tree]

Do you have a hot water tank for the domestic system heated from the engine? Check the connections at the tank end of so. I've just replaced mine and I started to lose a bit of coolant after 5 or 6 trips. Just needed to tighten the fittings up.

[Pedro]

I'll check again,,I didn't see any when I first looked,,thanks

[WillieC]

A leak somewhere inside the boat should make itself noticeable sooner or later. My coolant was going into the oil pan via failing gaskets or seals. I figured something was up when the coolant overflow tank kept filling up but would not suck back into the engine when it cooled down. A simple oil analysis confirmed my suspicion so I had a nice winter project. (Mine was a VolvoPenta, not Peninsular, but a leak is a leak.)

[kerrye]

Yes, I'd send an oil sample to Blackstone. They confirmed coolant getting into the oil in my 6.5 diesel.

[Pedro]

Thanks,,,Leak existed 4 years ago ,oil analysis showed nothing other than slight wear from a 21 year old motor,,

[Pedro]

Kerrye, We are doing a pressure test this week, if we can't pinpoint the leak,I'll send out an oil sample,What engine did you have? What was the solution?

[kerrye]

I had a 6.5 diesel in a GMC truck. Notorious for leaking coolant into the oil from the headgasket, holes in back cylinder walls or cracks in the lower block. Pretty sure the crack was in the lower block on mine. I replaced it with a new Optimizer long block. Far stronger engine than the original 6.5.

[Russell]

Have you checked the radiator cap?

[Pedro]

Yes,Checked and replaced the cap last season, no obvious antifreeze in the oil,
Antifreeze looks fine,,pressure test of heat exchanger is next.Engine runs perfectly well, and does not overheat,,

[Pedro]

Mechanic,serviced the aftercooler and replaced any hose he could reach,now I'm about 100 percent new on hoses on a 21 yr old engine.
Pressure tested heat exchanger and it never dropped after 1 hour of running?

[Pedro]

It appears as though the ne k on the heat exchanger was bent and the cap wasn't seating perfectly so no pressure,,
The mechanics pressure gauge has a much better seal so that why pressure test showed no leaks,only leaking ever so slightly do to fillercneck being bent, we straightened it and now coolant goes into the overflow when hot,

[WillieC]

Very good. My HX was hardmounted to the headbolts of my Volvo Penta shake and bake that tended to eat the rubber on the pressure caps. I moved the support to the lower engine box and rebuilt the engine. Which doesn't shake nearly as much as the old one. I suspect I won't be replacing pressure caps too often anymore.

[DougA]

Pedro, did fixing the heat exchanger neck fix your coolant loss problem? I have a similar issue with slow coolant loss, with pressure tests passing ok.

[DougA]

Engine is a 2014 Peninsular re-power.