Long story short we had a catastrophic coolant failure at Bristol Forest Rally, running about half a stage with no coolant at all (thanks to a radiator impaled on the PS pump). This of course blew the HG and probably cracked the head as well. Fast forward, a new/machined head is installed, new HG, everything runs fine, temps are good, not evidence of anything amiss, but I'm getting oily residue in the coolant reservoir (maybe a mm or two floating on top of the coolant). No coolant in the oil, btw.
I assume this is just oil that got into the system while it was totally empty of coolant ....so stuff just left in the block passages since the head and radiator are new.
So the question: I don't expect just flushing the system with water will get much oil out, though I guess it will slowly collect at the top fo the reservoir perpetually. Is there any kind of detergent/coolant flush stuff that anyone recommends to clean out the system? I don't want to get the new radiator or water pump to get gunked up if there's more than a little oil in there. I've seen the liquimoly radiator flush mentioned as a good option.
Btw, engine is a BMW M50.
The oil WILL make its way to the top and out. I had to deal with an STI where the person who installed a rotated turbo setup got the oil and coolant return lines backwards and it pumped all of the oil into the coolant and vice versa. It took a while but all of the oil made it into the overflow container. (Also, a GT35R on an STI, even at low boost, is a lot of fun)
I found some bulletin a while back where a manufacturer actually called out a product name for removing oily residues from coolant and cleaning the passages, it may have been Cascade (the dishwasher stuff). I still have half a bottle in the Batcave, will dig it up tomorrow if you'd like.
I have no personal experience with this, but have you considered Water Wetter? IIRC it's basically a non-foaming detergent designed for cooling systems.
Run it on the hose. Drain. Run it on the hose. Drain. Etc. Should get the bulk majority out I would think. Does the car have the self bleeding system or the crappy reservior mounted to the fan shroud?
I worked with an ex-Mercedes technician a while back, and he always kept a bottle of Mercedes brand citric acid powder around just for this reason. You fill the cooling system with water, add the citric acid powder and run the engine for a prescribed amount of time. It'll clean all of the oil residue out of the system.
I'm sure you can find something similar on Amazon or the local auto parts store.
In for this because my bmw made a similar oil/coolant snafu recently.
I had an '86 Celica GT-S that used more oil than gas, so I kept a gallon jug of oil in the trunk.
One night I went to add coolant and instead of the coolant jug, I got the oil jug. I knew once the minute it starting pouring I had messed up. What a nightmare that was, could never fix it
I sold the car.
