Kit is an option for glass damage

Question: Do you have any experience with windshield repair kits? These kits claim to repair small chips and cracks. Do these kits work and does the repair last over time?

-- E.M.

Answer: The kits are intended to repair fairly small damaged areas, either cracks or depressions that are called bull’s-eyes. If you have lived in Southern California any length of time, chances are you have dealt with a broken or damaged windshield more than once.

The problem is debris. We know from the Columbia space shuttle accident that even pieces of lightweight foam can cause damage. And debris is frequent on the messy freeways that cross Southern California.

The region is one of the largest gravel mining centers in the country and every day you can see single and double trailers hauling gravel, sometimes spilling their loads out of the top or through leaky gates at the bottom. Small rocks and other garbage that get kicked up on the freeway can slam into your windshield at 70 miles per hour.

Typically, damage occurs to one layer of the glass. All autos use safety glass that consists of two layers of tempered glass that surround a layer of butyl or other plastic. The system is designed to hold the glass together or fracture into cubes during accidents, reducing the risk of injuries.

Because most automobile insurers will waive a policyholder’s comprehensive deductible to repair a windshield, there isn’t much reason to do a repair yourself. A repair does not eliminate damage, but rather is intended to prevent it from getting worse.

Permatex is a major supplier of retail repair kits under the name of Bullseye. The kit contains a liquid bonding agent and a device that looks like a syringe. The liquid is applied to the crack or bull’s-eye depression and then the syringe is used to create a vacuum to cure the liquid.

Rene Patterson, a technician at Permatex, said the system works by penetrating through the exterior layer of the safety glass and bonding with the butyl layer inside. The product is not designed to fill the depression on the outside of the glass and will neither improve nor worsen visibility, Patterson said.

Shops generally will repair damage up to the size of a quarter, though some shops will repair cracks up to the size of a dollar bill. But by the time a car is 5 years old, the windshield already may be so pitted that it degrades visibility and a crack is a good opportunity to replace it.

Replacing a windshield typically can cost $250 and the vast majority of windshields cost less than $500. Comprehensive insurance will cover damage to windshields, but depending on your deductible, it may not make any sense to file a claim.

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Q: I have a 2000 Toyota Avalon. I make short city commutes with occasional freeway driving. I drive about 10,000 miles per year. When I took the car in for the 30,000-mile service, the service consultant wanted to do a transmission flush. I told him that if he could show me in the service manual where the manufacturer recommended this, I would have it done. Does this need to be done or were they just trying to provide an unnecessary service?

-- D.J.F.

A: The short answer is that more frequent transmission fluid changes make just as much sense as extra attention to motor oil.

Though manufacturers often recommend infrequent oil and transmission fluid change, such advice can lull car owners into a sense of complacency. A 30,000-mile interval for changing transmission fluid makes a lot of sense, given that an overhaul will cost more than $2,000.

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Q: My neighbors own three vehicles and they insist on revving the engines at start-up by pushing the pedal to the metal for several minutes. Often, they turn off the engines and restart them again minutes later. What is your opinion?

-- S.M.

A: Manufacturers and most car experts say that engines need very little time to warm up, perhaps as little as 10 seconds. Modern oil has very low viscosity even when cold and begins to flow in the engine almost instantly.

The idea of revving at high speed is idiotic and will probably damage the engine more than it will help. So maybe you can put this answer under their windshield wipers and let them know.