Oil and coolant in the bilges

[Breweryross]

Hi all…. Hoping for some advice…
I have twin Volvo Penta engines (Volvo AD31-p)

Both get up to top revs and sound good but I noticed a significant amount of oily coolant in the bilges after taking her out for the day…it’s just my port side.
Friends have told me that it’s the head gasket but an engineer told me that’s very unlikely. I’ve done the dip test and came back good,,, I think the coolant is coming from the pressure valve on the top so probably over heating… but why the oil too? And why might it be under heating?
Any thoughts much appreciated!!

Ross

 

[stelican]

Hi all…. Hoping for some advice…
I have twin Volvo Penta engines (Volvo AD31-p)

Both get up to top revs and sound good but I noticed a significant amount of oily coolant in the bilges after taking her out for the day…it’s just my port side.
Friends have told me that it’s the head gasket but an engineer told me that’s very unlikely. I’ve done the dip test and came back good,,, I think the coolant is coming from the pressure valve on the top so probably over heating… but why the oil too? And why might it be under heating?
Any thoughts much appreciated!!

Ross

There is a crankcase ventilator rear portside of engine with screw on filter and a relief valve should the filter be gummed up.
Mine always leaked a bit of oil.
Later engines where fitted with hose directing vapour back into rocker cover.

 

[Boaty_Pete]

Are you actually ejecting Oil and coolant, or is there a residual oil build up which has now mixed with the coolant and made said oily mess?
If your exchanger Cap is operating correctly and you have the small overflow pipe from the side of it (not completely familiar with your engine) you may be able to feed that pipe into a collection pot to isolated some of the symptoms.
Overheating may just be a symptom of needing a new impeller, or a descale on the cooling system.

 

[Plum]

Hi all…. Hoping for some advice…
I have twin Volvo Penta engines (Volvo AD31-p)

Both get up to top revs and sound good but I noticed a significant amount of oily coolant in the bilges after taking her out for the day…it’s just my port side.
Friends have told me that it’s the head gasket but an engineer told me that’s very unlikely. I’ve done the dip test and came back good,,, I think the coolant is coming from the pressure valve on the top so probably over heating… but why the oil too? And why might it be under heating?
Any thoughts much appreciated!!

Ross

If the coolant is coming out of the pressure cap then check the coolant level in the expansion tank when the engine is cold. On mine i maintain the level on the "Low" mark. If it is too full, when hot it will not have enough air volume above to absorb the expansion and blow out of the pressure cap. If that is all in order and you are still leaking coolant then you need to see where it is escaping when the engine is hot or, better still, get or make a pressure tester so you can check without running the engine. The coolant temperature gauge should be at 82 degrees running, is it?

 

[bowler]

A little oil already in the bilge could look like alot when floating on coolant.

 

[oldgit]

If the coolant is coming out of the pressure cap then check the coolant level in the expansion tank when the engine is cold. On mine i maintain the level on the "Low" mark. If it is too full, when hot it will not have enough air volume above to absorb the expansion and blow out of the pressure cap.

With all my previous VP engines and present Yanmar, when cold the plastic expansion tank was either virtually empty or only had a small amount of coolant visible in the bottom.
Under way and hot the bottle fills.

Any attempt to top up the bottle when cold , would simply result in the added coolant being promptly ejected into the bilge.
This would then result in oil weeps/oil vapour escaping old style crank case filters floating on the top of the coolant.
A quick suck with the Henry and then rinse again with hot water/washing up liquid usually restores a nicely smelling acceptable bilge.

 

[Plum]

With all my previous VP engines and present Yanmar, when cold the plastic expansion tank was either virtually empty or only had a small amount of coolant visible in the bottom.
Under way and hot the bottle fills.

Any attempt to top up the bottle when cold , would simply result in the added coolant being promptly ejected into the bilge.
This would then result in oil weeps/oil vapour escaping old style crank case filters floating on the top of the coolant.
A quick suck with the Henry and then rinse again with hot water/washing up liquid usually restores a nicely smelling acceptable bilge.

That is strange, filling to the LOW/min mark when cold always works on mine 41-P (same as the OP's apart from number of cylinders) and I don't have a crankcase filter so my bilge is always dry.

 

[FatherTed]

I had this problem 4 years ago and in my case the head gasket was gone & a leaking injector cup. (KAD32)

A couple of things you can do.

1) Make sure the small coolant hoses are clear and not blocked. If these are blocked you will get an airlock.
2) Make sure the small nipple on the header tank (for the small coolant hose) is not blocked.
3) Add a pressure gauge onto the small coolant pipe and monitor the coolant pressure, if it is too high, then head gasket/injector cups should be investigated. Typically, after a run my coolant pressure is average 5-7 psi. The header tank cap will trip at 0.75kpa (10.8 PSI)

I keep my coolant below the low mark and I watch on the camera in the engine bay. When coming off the plane and down to low speed you can see the coolant rise up in the tank, about 2" in my case and then it drops back.
I can also monitor my coolant temperature through the chart plotter, 84.5 when cruising, 86c at WOT, and then dropping to about 75c shortly after when running at 6 kts. Both engines exactly the same so it's good to have a comparison.

I do tend to over monitor things now as you may have noticed