Originally posted by e21jbk@Jan 7 2005, 04:21 PM
Hi there, I have once encounter quite the similar problem with coolant low and hissing sound on my E36,It took me quite a while to find out. In my case the thermostat housing was having the fine crack at the mounting position. The mech. must have over tightened or the the material (Plastic) give in.
I changed the thermostat housing,water pump and metal propeller as a precaution measure. after 2 weeks found the coolant low warning sign and keep topping up water to find the leak. At the end the Thermostat Housing was the culprit. Cost me RM98. for the housing.
You might want to check it out. Good Luck.