Bob Weber

Q: I bought a used 2008 Chevy Trailblazer several years ago. It is the right distance above the ground, and I really like it. When I drive for 30 or 40 minutes the voltage on the dash would go down. It still started normally, so I didn’t worry about it. Then, one day, it didn’t start. The tow truck driver jumped it and I went to get it fixed. They said I needed a new battery and alternator, so I had them replace both. After short drives, it seemed OK. The next long drive, the voltage went down again. I plugged it my digital voltmeter. After start, the voltage would go up to 15 volts, then gradually decrease, until it went down to 12.2 volts. I went back to the shop, and they replaced the alternator. Same story. Another alternator, same story. A different brand alternator, same story. The gauge on the dash shows the same thing, just not as precise. Is there something in this model that could cause this?

J.W., Evanston, Ill.

A: What you are seeing is perfectly normal. A fully charged battery will show 12.2 volts. Any drain on the battery, such as using the starter, lowers the state of charge — the voltage. It is the alternator’s job to get the voltage back up and it does this at a rate of 14.7 volts. That is close to your 15-volt reading. I would question the skill of a shop that replaces parts without a thorough diagnosis.

Q: Just outside Chicago, there is a sign that reads, “Engine braking prohibited.” On the east side of road are homes. The west side is industrial. Any idea what this sign means?

V.J., Palos Hills, Ill.

A: It warns truckers not to use jake brakes (engine compression release braking) or downshifts in the area. It is designed to protect the residents on the east side of the road from unnecessary exhaust noise.

Q: I have a 2013 Dodge Durango V-6, purchased new, with 44,000 miles. The last couple times I took it to my mechanic for an oil change, he pointed out coolant residue up and down the side of the radiator. He told me that I will soon need a new radiator, at a cost of $1,000. Interestingly, I see no sign of coolant leakage on my garage floor. To further check, I waited a few weeks and then checked my coolant level by removing the radiator cap one morning, before starting the engine. The cold coolant level was at the top of the radiator. When the engine is fully warm, the temp gauge reads below the halfway mark. I don’t believe I need a new radiator but am starting to think I need a new mechanic after all these years. What do you think? Thank you.

N.K., Minneapolis

A: If the leak travels along something hot, the coolant evaporates but like a garden slug, leaves a trail. That may be why there is no dampness on your floor. You may eventually need a radiator. But before you plunk down a grand on a new one, try some cooling system stop leak. Having used it, I can vouch for Bar’s Leaks brand. It was once used in the condenser of the 1958 Nautilus nuclear submarine.

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