Oil in Water-Oil Cooler?

[Ringo]

I saw oil sheen in water when flushing my Suzuki df140 last time. Checked the engine oil level and almost had already lost a quart of oil! Oil on the dipstick looked normal and engine performing very well. No alarms or hiccups what so ever. Called Suzuki last week and this seems to be from a known corrosion issue with the oil cooler for that engine model. Knowing that this part is the original has never been replaced by the previous owner, I did some research online and this is in fact a known problem. Is there a coincidence that this just happened after I replaced the thermostat a few weeks ago and now engine is getting warmer? Or is this just the case of a corroded part that needs replacement? The part itself costs $280 and it’s a 2-3 weeks wait to get it but I just don’t want to randomly buy and replace the oil cooler if there’s a way to diagnose the issue.
Any tips would be appreciated.
https://www.stripersonline.com/surftalk/topic/757455-suzuki-oil-loss-df140/

 

[ab1752]

Why not get one on order and pull your cooler in the meantime and have it pressure tested?

I don't think this could be related to a thermostat, if you have oil finding its way into the thermostat housing that would be rebuild time.

 

[CatchAll]

I had that problem on my Df140. I took the old oil cooler apart and it was totally corroded. I think the engine oil runs at a higher pressure than the cooling water, so oil gets forced into the water when the cooler starts to fail.

Maybe take it off and find a way to pressure test it.

 

[Ringo]

Will order the part tomorrow. There was no oil in the thermostat housing and also no drop in compression either. The Suzuki guy told me that the oil cooler on the class of engines should be replaced every 500 hours for the salt units. My motor only has 410 hrs but I guess it’s time for a new oil cooler as they don’t sell the o-rings individually.

@CatchAll did you end up replacing the cooler and did it resolve the issue?

 

[CatchAll]

@BCRingo Yes. I replaced the cooler and it fixed the problem. When was the last time you replaced the anodes in the powerhead? Lack of anode maintenance can cause parts like the oil cooler to corrode and fail.

 

[Ringo]

Good question! I replaced the anodes in 2018. However, there was no previous record of this work when I looked at the previous owner’s maintenance records.
Any idea if I need a torque wrench to install the new cooler? I looked online and it seems like I need a 1/2” deep socket for this thing.

 

[Ringo]

This is how a 15 YO oil cooler looks like on a salt unit.

 

[Ringo]

 

[turbomack]

I have had zero experience with outboards yet but looking at the build up on that oil cooler I would recommend circulating a product called Rydlime through your engines periodically to keep clean and promote efficient heat transfer. In my diesel powered boat the 6 coolers would pick up similar type of deposit which restricts flow and also reduces there ability to transfer heat. I would just mix a tank of Rydlime and circulate through the raw circuit of the engine with an electric pump for a couple of hours as part of my annual maintenance. It leaves the raw side of the coolers and water jacket clean and salt free which will promote maximum heat transfer.

 

[ericl]

The Suzuki guy told me that the oil cooler on the class of engines should be replaced every 500 hours for the salt units.

I would tend to think that there is at least SOME age-of-cooler versus hours-on-cooler component to this issue.

 

[Ringo]

I would tend to think that there is at least SOME age-of-cooler versus hours-on-cooler component to this issue.

I would agree. He said every 5 years or 500 hrs of service. I have owned this engine since there was 200hrs on it and have been religiously flushed it after each trip and with Saltaway every 3-4 trips but then there’s residual corrosion no matter what. I also checked and cleaned the anodes and there was no sign of build-up or corrosion. I guess every 5-yrs would make sense for replacing the cooler.