So here is the backstory on this truck. It was on ebay and did not sell, the seller then informed me that diesel was noticed in the coolant tank and the truck will be getting fixed, before it is for sale again. So an agreement was made up that the truck was to be fixed, then it was mine. The original owner took the truck to a reputable shop in Texas where all 8 injector cups were replaced.

On the drive home TO KANSAS I noticed that the tank was completely filled and pushing fluid out of the top. It quickly became clear that this was diesel again.

So anyway there is the backstory, now moving on to what I have done and fixed, and what is still happening.

I have been using a method to test which bank of the motor presumably has the injector cup issue. I remove both fuel return lines from the fuel filter housing, and zip tie them together sticking up and fill them with diesel. I then drain all the coolant, and pressurize the cooling system. The first time I did this I got the cooling system to 7 psi and within seconds saw visible bubbles coming from the passenger side bank return hose.

At this point the tear down of the passenger side began. All four injectors came out and the cooling system was pressurized again with all four cups visible. Of course the back cup was bubbling and spewing and clearly the culprit.

The old cup was pulled and obviously installed wrong and damaged in the process. I then cleaned the living hell out of all surfaces that contact the cup. A new cup was slathered up with loctite 691 (or whatever the number is) and carefully driven into place. The injector was installed and torqued within minutes to help seat the cup.

Time constraints did not allow for injector removal and a second pressure test to confirm that all was well. The night of the cup installation the motor was buttoned up and I then waited 24 hours before staring it up.

A mix of simple green and water was put through the motor for 30 miles or so, then the entire system was flushed for a long time with a garden hose. It was then refilled with new coolant.

So here's the deal. It is still putting diesel in the coolant, drive 30 miles and let it sit and you can see roughly a 1/16 of an inch of RED .....in the overflow tank. Drive more and it makes more.

So I went back to my original method of draining the coolant and pressure testing the cooling system, then looking for bubbles out of the fuel return hoses. Last night I had the system at 20PSI and stared and the hoses intently for 15 minutes while drinking bush light. There was not a damn thing out of the hoses.

Here is my question. What am I missing? Is there another way for coolant and diesel to mix? cracked head? All opinions are welcome.