Trace Oil in Coolant Sample CAT 3116

[peterkvs]

Back in the fall I changed the oil on my 3116s in my 99 400DA and sent in the oil and coolant samples for both engines to CAT SOS. The starboard engine report showed a trace amount of oil in the sample and the report suggested that I contaminated the sample when taking it. So I bought a separate sampling pump and took another sample recently. It still shows a trace amount of oil in the coolant. I have no feeling for what a trace amount is. I’m sure you can easily detect a drop of oil in a swimming pool of water, so I am not sure the severity of the issue and what I should be doing here. A cursory look at the web and a discussion with Frank Webster indicate the most likely suspect could be the Oil Cooler unless I somehow contaminated the coolant myself. So I thought I would ask you and see what your thoughts were. Just because I know someone will ask, the coolant levels have not changed in the last 200 hours of operation. I did have an issue a couple years ago with a cracked hose between the radiator cap and reservoir. There is 300 hours on coolant over 3 years.

Thanks,

Pete

 

[peterkvs]

Ok here is an update.

I got down to boat and did some more inspections and testing. The coolant in the port engine is very clean and uniform. I ran it up to 140 with radiator cap off and it produced a few bubbles but nothing I would say out of the ordinary. On the starboard engine, looking in the overflow tank there is a layer of brown scum on top of the antifreeze. In the tank on top of the engine there is some spooge floating around in there. I ran the engine at idle for a while and the spooge just kind of swirled around. Then I ran it at 1000 rpm and after a while when the engine warmed up a bit to maybe a110-120 it started making large bubbles like you would make with a soap solution and one of those bubble blowers, they would at least be 3/4" in diameter before they would pop. Once the thermostat started to open the coolant started to overflow the tank and so I shut it down. So I don't think any of that is very conclusive. No trail of small bubbles that I thought were the sign of a head gasket problem. But maybe that's not so on these diesels. Anyway, I have a pressure tester and a filling device (that I can use to look for bubbles without overflowing) that I can bring back for some further testing. I sure hope it is not a head gasket. Any idea what that costs to replace? How about replacing the oil cooler? Any previous experience here?

 

[barlow]

The value of fluid sampling has recently paid off for me also with metal found in a coolant sample. Faulty circulation pump replaced so drama averted. Good luck with the investigation.
Im certain with Franks guidance you will sort the issue.