Oil in Coolant

Here's what the end header looked like after I cleaned it up. You can see some scale deposits from the coolant, but nothing crazy.





And of course, the mess in the rad and expansion tank:

The end of the bundle looks ok, but there is some rust, which is a bit concerning. Three of the tubes were blocked. One of them was so tight with some crusty white stuff that I had to clear it with a drill bit (by hand). So at this point, I'm thinking to set up some kind of pressure test after putting the new seals in.

Well guys, what do you think?

Forgot to mention that I did drain some of the oil and no coolant came out with it. The truck was sitting cold for several days, so I'm pretty sure I would have seen something if coolant got in.

Here 2-3 yr ago I posted/started a thread "Oil Cooler rebuild BooBoo" where I had messed up rebuilding my oilcooler. Got many good ideas responses.
I also posted info & pics on how to build a test plate to test your oilcooler... post # 8 thru end of thread.
Russ- @typ4 @genscripter and several those guys had lots good info as well as tips.

Ditto on test the cooler. That corrosion around the o-ring could have done it. But heavy corrosion in a tube perhaps created a leak. These oil coolers are more than not the cause of oil in the coolant or visa versa.

When my oil cooler o-rings leaked coolant into my oil it was minimal. Oddly the coolant came out last during two oil changes. Like a teaspoon or two but it was the last thing to come out of the oil pan. It also did not mix with the oil either. Just sat in the oil pan separated. So you may want to drain all the oil.

Upside if it is your oil cooler, far easier than head gaskets. If not your oil cooler? You found two o-rings getting ready to fail and your oil cooler will now go several more years without issue.

Lets also get some members who have done head gaskets to chime in on symptoms and if oil in the coolant is common for a 6.9 head gasket leak. If they did have oil in the coolant was there also air from the compression stroke or exhaust stroke visible in the cooling system? (Bubbles, coolant pumping out, air coming out of the expansion tank, diesel exhaust residue, etc.)

Thinking out loud it would have to be a gasket failure at the perfect spot for the oil to push to the cooling jacket. These trucks do not have high oil pressure so at the head it would only be probably 10-20psi. Also with the coolant at 7-13psi with the engine hot I would expect coolant to flow into the oil when you turned off the motor and it sat. Unless the compression +/-400 psi or exhaust pressure was what was pushing the oil into the cooling system.

There is no pressure oil at the head deck.

wire brush the rust off the bundle sand the oring area, it should be fine.
Used many way worse.

As suggested, I cleaned up the areas where the O-rings are seated. There was a fair amount of crusty buildup on the oil/coolant seal, so maybe that's what the problem was. The black shaded areas are trace amounts of corrosion, but they are smooth. Most of the buildup was removed with the edge of a box-cutter blade, then the areas were sanded smooth by hand.




Rust on the end of the cooler bundle also cleaned up:

This next post comes with a disclaimer. I sometimes like to use permatex #3 aircraft gasket sealer. I'm not saying that this is best practice on a cooler reseal, but here's why I used it.

1. It has excellent oil resistance
2. It never fully cures, so there's no worry about chunks coming off into the oil or coolant (RTV is prone to this)
3. It offers some corrosion resistance as well. I've used this in the past on exterior bolts and it seems to prevent them from rusting. The idea here is to seal and smaller traces of corrosion on the O-ring areas.
5. It also worked as a lubricant for the seals while I pressed the assembly together.

The stuff is liquid (not a paste) and applies easily with the supplied brush. I only used a very thin layer.







I used the same sealer to stick the header gasket on. I did NOT apply any sealer to the other side, since they already apply some kind of sealant from the factory and didn't want to mess with that.

Here's photos of the correct OEM gaskets. The orange sealer on here had to be scraped off the flanges on the side of the engine block. So whatever the stuff is, it works well.





So just to recap, here's what I had to do for access to the cooler:

1. Unbolt power steering pump and set aside
2. Remove Steering shaft
3. Unbolt driver's side engine mount and lift that side by about 1".

Driveshaft and the front wheel stayed on. Also didn't have to mess with the brake lines, the brake proportioning valve bracket does hang up a bit. Overall, it took me about 3 hours to remove and another 3 hours to put back together (not including coolant).

My plan now is to separate as much of the oil as reasonably possible from the coolant, and then run the truck for a little while so the rest can get pumped into the recovery tank. Then comes the flush and coolant change.

All back together and running but not yet sure if the problem is solved.

I separated as much of the oil as I could from the coolant and put it back in. The rad is still full of oil, so I'm hoping the oil will work it's way out over the next several driving cycles so I can recover it from the expansion tank. Once I'm satisfied that the cooler is not leaking, I can look at flushing and changing the coolant. We're heading into winter at the moment, so using straight water isn't really an option.

Cascade dish washing detergent. Several times. The oil gets in places very tricky to clean.
Aviation seal is much better than RTV for the orings.
RTV cures, then shears if it moves, then you have a leak.

I've used liquid laundry detergent before. It seemed to work fine. It just takes a while to get all of the oil out.

Well, oil is getting pumped into the recovery tank. Still plenty of black oil under the rad cab but we'll have to see if the rad coolant clears up over the next few days. Engine oil still appears black, and not milky.

As I mentioned in (I think) post#9, I had to do 6 flushes with soap to finally get all traces of the oil out of the system.
Fill her up, drive the heck out of her to get her hot. Come home and drain the Radiator and the Brass Block plugs.

When she cools down fill her up and go again.
I forget , think these things hold something like 8 gallons of liquid. Not all of it will drain out on each drain cycle.

Don`t expect the old gunky oil to magically appear in the Over Flow Bottle and be done with it.

I also replaced the rubber hoses with new one`s when I was done.

Goat.