Hi, probably yet another topic on oil and coolant sludge but I can't find an answer to my issue.

2 weeks the r53 started to smell strange and smoke was coming from under the hood. There was a milky mix steaming out of the coolant reservoir.
After searching around, I found (on this forum) that there could be an issue with the heater exchange. So on good luck I just ordered a new one (including gaskets) and started to dismantle the part and cleaning up the engine.

The old part was blocked and dirty so that could be a sign that it is the heat exchanger. I flushed the radiator with a hose, tried to flush as much I could. Installed the new parts, added the coolant with a 'sludge cleaner'.
Run the engine for 15 minutes, flushed the coolant again and added new coolant again.

Now comes the issue: Although the temperature keeps ok, there is no sludge in the oil and there is not to much pressure or something, it keeps on creating a very small layer of sludge on top of the coolant in the coolant reservoir.
I can get it out but after a few miles there is a small layer again. (i have drive it now for a few days)

Should I fear the head gasket (leaking between oil and coolant). Or could this be residue sludge in the coolant hoses/radiateur, interior heater?
I'm curious on your thoughts.

Although it is a 2004 car with 240000 miles on it, we like the car, it looks perfect and we want to keep driving it

 

How long has it been since swapping out the heat exchange? It's probably is just a little residual sludge working its way out. If it's still doing it after another 1000 miles, I would look further into it. Just keep up with your fluids for the time being

 

I think I only drove it 50 miles now in total after the exchange. I will keep an eye on the fluid.