My 1991 780 coupe w/ 230bft engine has a white substance showing at the exhaust pipe just past the turbocharger. This appears to be coolant/water deposit due to its look. The engine runs well but for a rich cold start, even after replacing the F.I. temp sensor and cleaning throttle body and idle control valve. I have scoured the FAQ's on Turbo, but no mention of what I am experiencing. I lose enough coolant after about 500 miles to get a temp gauge overheat reading, not quite reaching the red zone. Turning the heater on helps temporarily until I am able to fill up the overflow tank, and the overheat problem is solved for the time being. No moisture/sludge visible in oil. No excessive exhaust moisture at tailpipe. Just the white deposit around the exhaust manifold to exhaust pipe fitting. Any help is appreciated in advance.
This is a way fun car to drive. P.S. - new radiator installed 30k ago, w/new pressure cap. No other obvious leaks of coolant.