I had a huge oil cooler failure a couple weeks ago. Pushed almost all of the oil out of the radiator cap in a fairly short period of time. I installed new orings and gaskets and flushed the coolant (admittedly not nearly enough).

Ran it for for a couple hours between getting the coolant refilled and test driving and some other short drives. Seemed fine other than coolant looking terrible, but I had to take a trip and felt it would be ok.

Made it about 350 miles with a constant coolant level (stopped a few times for fuel and snacks), then it started pushing milkshake out of the bottle again.

I also just realized that the washer I found on the floor after the job was part of the bypass assembly. Obviously I need to rebuild the bypass or buy a new head, but trying to decide if I should order a new cooler also. I wouldn't think it would have made it 350 miles if the cooler itself was broken somewhere??

 

It's not likely the oil cooler itself, but it is likely things went wrong during the rebuild. The O-ring seals can get scraped on rough surfaces if the cooler lips aren't smoothed over, or the flat gaskets can get damaged while fighting the rebuilt cooler into place. I suffered both when I had a shop do the work - so I had to do it myself to get it right. I likely would have made the same mistakes, but I learned from his.

This is what I found when I dissected the failed oil cooler rebuild:

 

Rich is right. Damaging an o-ring or gasket is easy to do. It can happen with even the best prep techniques, but can happen even more easily if proper prep is not done on mating surfaces before re-assembly.

I try to never scrape mating surfaces with sharp edged tools like scrapers or screwdrivers because they can leave leak paths by leaving deep scratches or cuts in mating surfaces. I have used razor blade scrapers in a few extreme situations, but I try to avoid it if at all possible.

After getting all gasket or RTV residue off, I typically polish mating surfaces with 400 grit wet/dry paper followed by 0000 steel wool. If there are any burrs, the steel wool will catch on them and I then dress down the burrs until they are gone. My oil pans, manifold faces, intercooler boot surfaces, oil cooler heads and tubes, clamped hose connections, water pumps, oil filters, valve cover gasket contact surfaces, fuel bowl lid, thermostat housings, etc.... they all get that treatment when they are opened up, and I even sometimes will use an extremely thin film of the appropriately rated RTV on gasket faces to both hold them in place during assembly and provide a small degree of extra leak-proofing "insurance". It is also very important to lightly grease any o-rings before assembly.

The above prep techniques have almost never left me with a leaking joint after startup. The only (few) leakers I've experienced after the above cleaning and polishing technique have been when I accidentally let the o-ring or gasket slip out of place during assembly.

For your situation, once you have the oil cooler re-done, I would purge the cooling system thoroughly with water with the engine running by leaving the thermostat out of the system and use one of the old-fashioned flushing tees in the heater line with a water hose attached to it. With the stat out, engine running, and water hose turned on, you'll be able to thoroughly flush the engine and heater core to get that nasty milkshake out.

 

When flushing a coolant system to get the oil out, an old timer told me a few weeks ago that Cascade dishwashing detergent was a good detergent to use. It doesn't foam up, and cuts the grease. He was replacing a radiator in a Peterbilt that got oil in the cooling system.

 

Gotta love the "hillbilly mechanic's" with the cargo strap!

 

Thanks guys, great advice. I prepped all surfaces with Emory cloth followed by green scotchbrite, but went with trans fluid for oring lube due to limited time and nothing better nearby.

I also used a floor jack; I think a strap would have been better. I think I even had one nearby just didn't think of it.

i was also thinking that surely a little silicon would have been a good idea to hold the gaskets in place since they kept sliding out while I was trying to get the bolts in. I think I will use some this time.

I was planning to just stick a garden hose into the lower hose after removing it from the radiator. Also was going to use a little purple power or simple green.

Seems obvious now, but I didn't remove the stat last time so will be sure to do that the 2nd time.

Currently only pushing about a quart an hour into the overflow. I think it was pushing quarts per minute the last time. I was really surprised that the leak path wasn't obvious then so don't expect I will find it this time either.

 

When flushing the system with the thermostat out, do not forget to turn the heater on in the truck. I also remove the coolant return from the drivers side of the degas bottle and drain that into jugs/bucket for waste storage.