A few months ago I purchased a 1990 735il and have had cooling problems with it ever since. It started with intermittent leaking at the seam where the lower radiator hose meets the thermostat housing. Eventually, the lower radiator hose blew out. I replaced it, but as soon as I started the car it immediately overheated. My next step was to change the thermostat. (Note: When I removed the old thermostat it was obvious that the person who had installed it had snipped off the inner portion of the thermostat. I don't know why someone would do this, but I figured it must have some significance). When that was done I thought I had solved the problem. The car drove perfectly on a 50 mile drive after replacing the thermostat. A few days later I was sitting at idle and the car began overheating again. I shut it down, let it cool off and drove home without issue. It now seems to run fine and the temp gauge stays at 12:00 as long as I keep driving, but when at idle it seems to overheat.
It should also be noted that there seems to be some oil getting into the coolant system. I am making plans to replace the head gasket at this point, but only seems to be a one way problem as there is no evidence that coolant is getting into the oil. While every response is appreciated, I am not much of a car guy, so if you could keep your advice in layman’s terms that would be great.
Thanks.