If you’ve ever considered putting a bag of rock salt in the trunk of your BMW 2002 during the winter, here’s a tip: don’t.

When they break, as they always do, those corrosive crystals scatter everywhere and in a year or two, you’ll notice a patch of gasoline forming on the garage floor. It’s gas tank leak time!

Even if you’ve not got a gas tank leak, I’d suggest you pull the tank the next time it’s near empty and check for rust along the seams. Following the steps in the Service and Repair Handbook, (mine’s a Clymer and it’s great).

1. Disconnect battery ground strap.
2. Remove tank drain plug.
3. Remove trunk floor panel and expose tank.
4. Disconnect the electrical leads on the sending unit.
5. Disconnect fuel hose from sending unit.
6. Detach hose clamp at bottom of filter neck and push rubber sleeve upward (also disconnect fuel return line and plug is on post-73 cars).
7. Unscrew fuel tank securing bolts and lift out the tank.

If you see any signs of rust or corrosion, steelwool them down to bare metal and spray on three to four coats of rustproof paint. The preventive care is well worth the effort, as BMW 2002 tanks cost $80-$100 to replace, and welding or soldering a leak is not without its drawbacks.

If you do have a repairable leak, shop around until you find a gas tank repair shop that fills the tank with inert gas, not water, before welding. The guy who fixed mine steam cleaned and submerged the tank and now, a month later, I’ve had to clean the fuel pump filter, replace fuel line filters twice, and pull and rebuild the carburetor. A clot of rust doesn’t do much for an idle jet. After all that, it looks like I’ll be able to keep up with the sludge accumulation by pulling and rinsing the tank once more and changing fuel line filters again.

Believe me, the half-hour it takes to remove and clean the tank is well worth the effort.

Author: Kevin J. Craw

Tech Ed. Note:

The rust, more likely than not, was scale in the tank. After the repair, rinse tank out with a gallon of gas and dump it.

Gas tank leaks are caused more often by the sponge rubber that the tank is mounted on. This rubber catches the water thrown up by the rear wheels and causes the tank to rust out. I’ve replaced many gas tanks on 3 year old cars where the owners never had rock salt in the trunk compartment. Possible cure? Remove the gas tank when it’s a year old, clean the rubber, and spray a good undercoating on the tank after wire brushing it and painting it with a zinc chromate-based primer