Tom's Corner Garage: Mechanic in a Can

This weekly feature for Edmunds Daily about car repair and maintenance is written by Tom Torbjornsen, the popular host of America's Car Show on satellite radio.

Dear Tom,
Is there a product on the market that can stop oil from leaking in an engine? My Lexus is leaking oil and I was quoted $1200 to fix it. I don't have the money and want to drive the car. Please help.
Linda from Little Rock

Unfortunately for Linda, no product stops oil leaks. The only way to stop an oil leak is to restore the sealing capacity of either the mating surface or the seal. Mating surfaces must be clean and have enough material to fit securely to a gasket or seal. Seals and gaskets must be flexible and pliable so that they can form a tight seal against the mating surface.

Linda is going to have to find a way to get it fixed, and brings up a hot topic. This one falls under the category I call "Mechanic in a Can." Some companies take advantage of the ignorance of consumers, and promise them instant cures for mechanical problems by simply adding their wonder elixirs. Be wary of products that claim to "Stops Engine Oil, Transmission Fluid, and Coolant Leaks," and here's some straight talk surrounding these snake oil compounds.

Engine Oil and Transmission Fluid Sealers
This category of chemicals, when added to engine or transmission oil, restores aged-hardened rubber seals that are leaking so that they are once again soft and supple. As the seals swell, they tighten against the mating surface and the leak stops. However, in short order the sealer chemical wears out, the seals return to their hardened state, and the leak is back. It is for this reason I do not recommend using these products. Have the component re-sealed or rebuilt. You can't restore rubber to seals, nor can you restore metal to sealing surfaces. Don't waste your money on such foolishness. Fix the problem or risk causing more damage (and that means more money out of your pocket in the long run).

Radiator Stop Leak
These chemicals are designed to course through the cooling system to the location of a leak. When the stop leak product finds an exit from the cooling system, it starts to close the leak by "building on itself" as it exits the system. However, problems arise when system pressure is restored, which in the case of aged and brittle radiators means another leak can spring up. In addition, "stop leak" tends to stop up other small orifices in the system such as heater cores, causing it to malfunction. Finally, I have seen so much stop leak used in an engine that it literally clogged up an entire bank of water jackets. These are passageways lining the cylinder walls through which engine coolant flows, transferring heat away from the engine. This stuff harms more cars than it fixes.

'Til next time...Keep Rollin'

Posted by

Paul Seredynski July 1, 2009, 11:00 AM

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