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gmc70 · 03-11-2021, 05:41 PM

We have a 2009 HR vacationer with Cummins ISB. I discovered water in oil this week. Being a car guy my first thought was head gasket [oh no] . Upon talking with a very experienced diesel mechanic he stated that 95% of the time it is the oil cooler and that blown head gaskets on that engine are very rare [hope so]. Does anyone here know or have any experience where to find the thing and changing it out?

Skip426 · 03-11-2021, 05:47 PM

The engine oil cooler on an older ISB 5.9, is directly behind the oil filter . Oil filter , alternator and depending on location , dash A/C compressor , would have to be moved for access.

I'll see if there is any different info out there.

Fogbelly · 03-11-2021, 05:48 PM

Quote:

Originally Posted by gmc70

We have a 2009 HR vacationer with Cummins ISB. I discovered water in oil this week. Being a car guy my first thought was head gasket [oh no] . Upon talking with a very experienced diesel mechanic he stated that 95% of the time it is the oil cooler and that blown head gaskets on that engine are very rare [hope so]. Does anyone here know or have any experience where to find the thing and changing it out?

I've heard you can use divining rods to locate the water source.

Jim_HiTek · 03-11-2021, 06:09 PM

I owned a '94 Cummins 5.9 ISB and it had that 'oil cooler' leak. Oil getting into the water indicates a pressure leak, and the tech told me that the only way that happens is via the oil cooler. As I recall, it doesn't go the other way. So, I'm confused by what your tech told you. Are you sure it's water in the oil, and not oil in the water?

In my case, when the antifreeze was drained, we could see a sheen of oil on the surface. Which is the tip off of the oil cooler leak. The oil cooler on my model, as I recall, is under a plate on the drivers side of the engine rearward of the turbo. Not easy job to replace so I just let it ride and years later, no big issues. I did need to replenish the oil on occasion as everyone does with or without that leak and the amount of oil in the AF didn't seem to increase a lot over time. Don't recall draining out the AF for that reason. I gathered that oil in the AF isn't very harmful. But water in the oil, that's bad.

One of those cases where letting it be was the low cost method.

Skip426 · 03-11-2021, 06:22 PM

I can't find any indication of differences over the years on location .
Here's a picture of the oil cooler and one showing the cavity in the block where it fits.
A Google search for ; ISB oil Cooler ; will provide MANY more.

Jim_HiTek · 03-11-2021, 06:27 PM

Yep, that's where mine was.

96 Wideglide · 03-11-2021, 07:04 PM

Another thought.

Since you have an 09 coach, it could possibly be the EGR valve/ cooler.

twinboat · 03-11-2021, 07:05 PM

Bad Oil cooler pushes oil into coolant. You find it under the radatior cap. Oil floats on coolant

Coolant into oil is cylinder erosion, cracks in the head or head gasket. Coolant comes out the drain plug first or if run, turns the oil into dirty milk. Coolant eats the crankshaft bearings.

Ljwt330 · 03-11-2021, 07:33 PM

Just a question.

Yes, when operating, the oil pressure exceeds the pressure of the coolant system so any leak would force oil into the coolant. But what about on shut down? Oil pressure drops to zero, yet the coolant is still pressurized. Could not coolant migrate into the oil in that situation? At best, there would be oil in the coolant and coolant in the oil.

FL420 · 03-11-2021, 07:45 PM

I pre-tripped a school bus one day and found water on the dipstick. Turned out to be leaking cylinder liner(s).
[emoji40]

Jim_HiTek · 03-11-2021, 07:52 PM

Quote:

Originally Posted by Ljwt330

Just a question.

Yes, when operating, the oil pressure exceeds the pressure of the coolant system so any leak would force oil into the coolant. But what about on shut down? Oil pressure drops to zero, yet the coolant is still pressurized. Could not coolant migrate into tje oil in that situation? At best, there would be oil in the coolant and coolant in the oil.

Never had AF in my oil over several years of driving it after learning of the issue. But I did follow the recommendation by experts to always let the engine cool down after a long, steep, or high ambient temp run, which would also cool down the coolant.

An example would be climbing a steep hill and having the coolant temp rise up to 3/4 and then stopping at the peak and shutting the engine off without letting it cool first. That would be bad.

There were a few times when I would park, and set the cruise at 1500 RPM (big rigs CC's are designed for that) and wait until the temp gauge was down to normal for my engine before shutting it down.

96 Wideglide · 03-11-2021, 07:56 PM

Quote:

Originally Posted by twinboat

Bad Oil cooler pushes oil into coolant. You find it under the radatior cap. Oil floats on coolant

Coolant into oil is cylinder erosion, cracks in the head or head gasket. Coolant comes out the drain plug first or if run, turns the oil into dirty milk. Coolant eats the crankshaft bearings.

Twinboat, could the coolant from the EGR cooler, make it's way into the sump?

Skip426 · 03-11-2021, 10:40 PM

Quote:

Originally Posted by 96 Wideglide

Twinboat, could the coolant from the EGR cooler, make it's way into the sump?

I retired , the year Dodge /Cummins first came with the EGR cooler; and only saw a few , but can't think of a way , for coolant leak at the EGR cooler to get into the oil pan ; leak would go, with the exhaust gasses, to the intake manifold through the cylinders and out the exhaust.

twinboat · 03-12-2021, 02:44 AM

Quote:

Originally Posted by Ljwt330

Just a question.

Yes, when operating, the oil pressure exceeds the pressure of the coolant system so any leak would force oil into the coolant. But what about on shut down? Oil pressure drops to zero, yet the coolant is still pressurized. Could not coolant migrate into the oil in that situation? At best, there would be oil in the coolant and coolant in the oil.

Its possible, but the 60 + PSI oil pressure pushing into the coolant will show up first and faster. You will see oil pushing out the 16 lb radiator cap.