Discourage Mildew to Rid Car of Musty Odor

Question: I have owned a 1988 Mercury Sable LS since 1988. Beginning about two years ago, when the car had 13,000 miles on it, I have smelled a strange musty odor coming from the ventilation system.

The smell appears whether I have the control on vent, air conditioning or heat.

It persists for a few minutes and then goes away. I returned the car to the dealer four times and used a deodorizer, but that only masked the problem briefly.

On my last visit, the service manager said it cannot be fixed. What’s your advice?

--Dr. W. M. F.

Answer: As a medical doctor, you must be familiar with fungus, a lower form of plant life that thrives in dark, damp places. Mushrooms are one example of fungus. Athlete’s foot is another fungus.

Mildew is a type of fungus that produces musty odors and can ideally grow in the evaporator core of your car’s air-conditioning system. The evaporator core looks like a small radiator, except that it contains refrigerated coolant and is inside your dashboard.

After you operate your air conditioner, the core becomes quite cold and gathers condensation, much as a cold beverage glass forms condensation on its surface.

When you shut off your car, this condensation has no where to go. Pretty soon, mildew begins to thrive and poses quite a problem for allergy sufferers.

Some cars have greater problems, owing to the surface treatment used on the evaporator core. I have heard of many home remedies to the problem, but none is foolproof.

The simplest solution is for you to simply run the air blower with uncooled outside air for a while before you turn off the engine. This should help dry the evaporator core and reduce the mildew growth.

Another solution I have heard of but never tested is to find the ventilation port intake, typically near the windshield, and spray Lysol disinfectant into the intake while the air conditioning system is operating. That should kill the fungus.

Obviously, if you are allergic to Lysol, you won’t want to do this.

If the only problem is the odor, I suggest you just live with it. It probably isn’t hurting you, and replacing the evaporator core probably isn’t worth the huge expense.

In a past column, I reported on a new engine-cleaning system, called Sludge Free, which is offered at many quick oil change garages.

The Sludge Free treatment involves pumping a cleaning solution through your engine when the oil is changed, washing away soft engine sludge from oil passages and the bottom of the oil pan.

The machine forces the solvent through the engine at 42 pounds per square inch pressure, heated to 110 degrees. The service costs $39.95.

Is a Sludge Free treatment good value? Ted Titmas, Sludge Free president, asked that I have the treatment performed on my own car and report my findings.

The Sludge Free machine was hooked up to my car one morning in late December. I can honestly report that the oil has run cleaner since the treatment. My mileage has not changed and my car runs no differently than before the treatment.

Separately, Titmas submitted reports from a testing laboratory that showed a series of test cars had improved oil pressure and lower carbon monoxide emissions in their engines after a Sludge Free treatment.

Oil experts say a Sludge Free system might have benefits for car owners who have not regularly changed their oil and whose engines may be particularly dirty. But new oils are also better than ever at combatting sludge, they say.