Coolant flushing has been done to death. I know because I've read a lot of the threads. So why, you might ask, am I starting a new thread? Good question.

I recently bought a 2003 R53. The seller indicated that it needed a new head gasket. The symptom was significant coolant in the oil. A compression test showed reasonable compression on all cylinders. Rather than dive into a head gasket replacement, I decided to investigate the oil filter housing and oil cooler. This is what I found (I'm getting to the flush question, I promise):


So clearly some oil was getting into the coolant as well, though the coolant didn't appear oily. While the picture above shows the worst of it, there is some residue throughout the system. As far as I can tell, the radiator is ok. The further away from the expansion tank, the cleaner everything is. Here is the t-fitting to which the lower expansion tank hose attaches:


This is the upper radiator hose (much cleaner but still some dried residue):


I want to do a flush similar to the one in the picture below. They ran several buckets of a detergent mixture through until the returning liquid was clear. It's from a thread on the forum detailing a similar but MUCH more severe version of the problem I have.
https://www.northamericanmotoring.co...acks-this.html


I have a new oil filter housing/oil cooler, thermostat housing, and thermostat ready to go in as well as the coolant hoses to the oil cooler. Ideally, I'd like to flush the system before installing them. That's not a problem for the thermostat and housing. In fact, I've removed the old thermostat but left the old housing. Will install the new ones after the flush. It's more of a problem for the oil filter housing. I can't put the old oil cooler back on the car because the internal passages are likely blocked, at least partially. But I'm concerned that putting the new oil filter housing and oil cooler on prior to doing the flush will contaminate the new oil cooler. I might be overthinking it. Any thoughts or suggestions?

 

When we had cross contaminated cooling system in cat machines we used the powder form Cascade dish washing powder. Mix it with water and fill the cooling system, run the machine for a little while, drain refill and do it again till the water comes out clear. Strong enough to clean the cooling system but gentle on aluminum parts. Flush the system with water and then fill with coolant.

 

Thanks for the reply. I was planning to use Cascade once or twice followed by several rounds with a LiquiMoly coolant flush product that has good reviews. My biggest question is whether to install the new oil filter housing and oil cooler before doing the flush. If not, I'm not sure how I'll be able to run the car to circulate the water/cleaner mixture. I assume that getting this hot will help with the flush.

 

I would install the new oil filter housing and then run it. I don't think it will hurt anything

 

I had a thought. I can install the new oil filter housing but not connect coolant hoses to the oil cooler. Instead, I can use a hose to tie together the two hard lines that lead to/from the oil cooler cutting the oil cooler out of the loop. This will circulate coolant throughout the system without risking contamination of the new oil cooler. The engine will only run at idle to flush the system so I don't think there's risk of the oil getting too hot.

 

I would say that would be a good choice.