Elusive Coolant Loss
by Pete Lautares
Tidewater Chapter
If you're having to add about a pint of coolant to the reservoir every 2 to 4 weeks, as I was on my 533i, check the following. Ensure all hose clamps are tight and hoses are in good condition. If you have drips/puddles under the car, try to trace back to the source (sometimes a black-light helps the fluid stand out). If it's going out the tailpipe, that sweet smell of cash burning, you've got a blown head gasket. Stop reading and pull out your wallet. If not, read on. Look for telltale residue of dried coolant on the top and sides of the radiator around the auxiliary fan switches, the nipple for the overflow hose, and along the seams where the plastic sides and the aluminum radiator are crimped together. The seal/seam contains a gasket that will wear out and can be replaced for less than a new radiator but it is strictly a one time repair. If residue is found, clean it off and drive for a few days, then go back and see where it came from. In my case, I discovered a small hairline crack on top of the radiator. I used some epoxy stuff call J-B Weld to stop the leak. Whatever you use, be sure it works on plastic, some epoxy won't, and spread it 1/2" or more beyond the crack. I no longer have a leak and it sure beats the cost of a new radiator.
Comment from Chris Behier: A badly blown head gasket will show up as excessive steam out of the tailpipe. If it is the head gasket that is blown, do not continue driving the vehicle as the head can and will warp - increasing significantly the cost of the repair.