Fairfield-Echo

Q I purchased a used 2001 Chevrolet Malibu with a six cylinder 3.1-liter engine. It has 40,000 miles and has been well-maintained. When the engine is cold it sounds like the lifers make noise. When the engine warms up it runs fine with little noise. It has been making this noise for quite some time. My local dealer tells me to not be concerned. Is this common with this particular engine? B.C., Soldotna, Alaska

A This is a common complaint. The noise is called piston slap. It's caused by excessive clearance between the cylinders and pistons. Once the pistons warm and expand, the noise subsides. General Motors received many complaints about the sound. To cure the noise, engineers developed a replacement piston with a polymer coating. At first, the new design pistons were placed in cylinders five and six. This cured the sound for those two cylinders but the remaining cylinders developed the sound. As a result, dealerships were notified by General Motors to replace the pistons in the remaining cylinders with polymer coated pistons. This work was performed when a customer complained about the noise during the warranty period.

You can ask your dealer about this. There is a technical service bulletin that addresses the cause and correction procedure. The reference number is 01-06-01-005 dated Jan. 16, 2001. Also you can hit the National Highway Traffic Safety Administration Web site at www.nhtsa.gov to read a condensed version of the technical service bulletin.

Check the water pump

Q My 1994 Chevrolet Caprice Classic with 79,000 miles leaks antifreeze. It's a slow leak. It never leaks when it's running, but when the car is parked over night, I find a little puddle on the ground in the morning.

The leak stopped during the winter. Now that it is warming up the puddle has returned.

Two different shop mechanics have examined the car. One guy told me that he believes that the water pump is leaking but he's not sure. He says to wait until the leak becomes worse before replacing the pump. I'm planning a trip to Florida from Minnesota. Do you have any suggestions? G.G., e-mail

A The leak could be from the water pump. Sometimes the shaft seal on the pump only leaks when the engine is off. With the car placed up on a hoist a close examination of the water pump likely will reveal a trail of dried coolant from the water pump weep hole and probably a few drops of coolant. If examination verifies a leak, replacing the pump is the cure.

Since you are taking a long trip ask a technician to check all of the cooling system hoses. They should be supple and not brittle. Replace cooling system hoses that are brittle, cracked, leaking, too soft or bulging.

Also, make sure that a fresh supply of coolant is in the system. It should protect against freezing to around 40 below zero, even though you are traveling to Florida.

It's imperative to have proper antifreeze protection to prevent the engine from overheating. The air conditioning system can cause weak antifreeze to freeze.

If it freezes, the engine coolant will not flow to cool the engine. This causes a dangerous overheating condition that could severely damage the engine.

Check history before purchase

Q I'm considering the purchase of a new 2007 or 2008 Chrysler minivan, but I don't understand a few things. J.D. Powers reports that the minivan is great, but Consumer Reports gives them their lowest reliability rating. Also, I see thousands of them on the road. What have I missed? G.B., e-mail

A You haven't missed anything. The Chrysler minivan is a popular vehicle. It serves a wide variety of uses for all types of lifestyles from commercial use to hauling a soccer team. In one day it can make a morning run for garden mulch and in the evening it can travel downtown for a fancy night on the town. This is one reason you see so many on the road.

J.D. Powers provides an initial quality rating based on new customer impressions. Consumer Reports surveys their base long after the purchase. As a result you encounter two different survey results. Owners love their new vehicles and more than likely have not had any trouble with them. Motorists who have owned a vehicle for a couple of years are more likely to have had some kind of repair performed so the vehicle gets a poor rating.

No one can predict what your experience will be with a new minivan so base your purchase decision on the vehicle's history and your needs.

Oil filter has limitations

Q In a recent column you addressed the importance of oil changes and how dirt and grit wear an engine. You didn't mention the oil filter. Doesn't the oil suspend dirt and grit which is carried to the oil filter? Why aren't there more additives in oil? P.B., Osceola, Wis.

A You bet that oil suspends grit and grime. One of the most important jobs of oil is to clean the inside of the engine. It also carries the contamination to the oil filter. The oil filter does indeed remove most of the dirt and grime. Eventually the oil filter becomes full similar to a garbage becomes full. Once this occurs, grit and grime is not filtered and is circulated back into the engine. Also, the filter doesn't remove everything. It doesn't have the ability to remove fluid contamination and small bits of abrasive material.

As for more additives in the oil, there is a complex chemical structure that has to be balanced in order for oil to do all of its jobs. Adding more chemicals upsets the balance. Oil is supposed to lubricate, clean, cool and seal parts in the engine. This is a huge task that is constantly changing therefore the chemical balance has to be as perfect as man can make it.

Phil Arendt is an automotive columnist, consultant and

ASE-certified master technician. E-mail him on the Web at

www.drgizmo.ws.