Lately, I have had to add coolant (about 10-15 oz's) to my 1993 Volvo 940 every 100 miles or so. There is absolutely no noticeable signs of any external leaks. The car runs fine with no white or blue smoke in the exhaust.(White smoke would be telltale of a blown head gasket.) The only symptoms of note were that when I turned on the heater, I noted a bad smell coming out of the vents. Maybe the heater core is leaking and when the coolant vaporizes, it is being blown into the cabin. I thought that this may the problem however, I have since turned off the heater and the depletion of coolant has continued.

Any thoughts will be appreciated!

Thanks,

OnlyVolvo