Water in oil with a AQ130C and AQ270 drive

So...

It started with water leaking from somewhere around the oil cooler. I replaced the o-rings front and back (water intake/outtake) and it stopped leaking, but now it was leaking from the cooling pipe entering water in the oil cooler. I sealed it with liquid sealant. Problem solved...at least in terms of leaking water.

Next day when for a ride...upon return, port side of engine room completely covered in white slush. The ride went fine, the only thing was that it became very hot apparently based on my temperature gauge. So I gave it a break before returning to port.

My guess...it could be a blown head gasket, a cracked head (hope not), a failing o-ring behind the impeller, or a failing (leak) oil cooler. Since the oil cooler was giving the problems in the first place, started with that.

Bypassed the oil cooler completely with a hose connecting directly between water pump and manifold. Changed the oil now for the third time. 2nd time oil still looks a bit milky, but not as much as the 1st batch. We'll see what the oil looks like tomorrow. Had the motor run warm before changing the oil and rinsed the inside with a bit of diesel as well. Maybe we need at least 3-4 oil changes for all the water to come out.

I also took off the oil cooler today and tried to blow through the water inlet, while blocking the water outlet. Couldn't...so my guess is, the little water canals inside the oil cooler are not leak. Am I drawing a most likely correct conclusion? No air appeared to be leaking out of the oil canal. Of course, I have no idea how much psi I can blow and how much psi is normally put on there.

So...if the oil cooler appears to be ok...what then caused water to go in the oil? Providing that there isn't any water coming in the oil right now anymore. Not fully sure that is the case. Will do a compression test tomorrow and check the waterpump. I haven't really stress tested the engine yet. Maybe that is also something to have a look at...

Any tips, ideas? Your help is really appreciated.

Ps. I left the oil cooler out for now (that is bypassed, oil is not cooled at the moment). Not sure whether I really need to reinstall it eventually...the oil doesn't feel very warm when I ran the engine for about 20 minutes at 1000 rpm and shortly 1-2 minutes at 3000 rpm.

Oil cooler has 40 to 60 pse oil pressure on oil side and just a few psi (or even a slight vacuum) on the water side. Compression check should give you more info.... and yes, you need the oil cooler.

I compression tested the engine:

Dry: 135 135 120 135
With a teaspoon oil added: 150 150 140 155

I know the compression values are too low, but given that they're similar across all four cylinders, my guess is they are not necessarily bad. I've heard anything above 9 bar is good enough. But this could be due to worn piston rings?

Back to the water in oil problem...it wasn't the oil cooler. I checked the water pump and this doesn't seem to be the problem either. So...what is left is a leaking head gasket or a cracked head (hope not).

Any other issues that you know of that would cause water to mix with the oil?

What I - however - don't get is, if here is a leak in the head gasket, how water could come in the oil? The oil/exhaust system pressure is always higher that the water pressure, isn't it? Then how it is that water is coming in to the oil carterpan etc?

The other thing that I noticed is that when I crank the engine and the water inlet hose between manifold and waterpump is not connecting to the waterpump it shoots out (remaining?) water actually with quite some force. Is this behavior normal?

I also tested the engine on the dry with a bucket of water connecting to the water inlet hose before the waterpump and never saw any exhaust gasses (bubbles) in the water, so...

Not sure what the water/exhaust gasses flow is in the manifold. Any drawings to show this online?

Problem solved...replaced head gasket and manifold was cracked.