Q: A friend put new motor mounts in my car and changed the fluids. When I got my car back, it sort of growled when I pushed on the gas to start. That was about a month ago, and now it is not as bad. Can you tell me what is wrong? Is it a problem?

—Dorothy Beardslee

A: It sounds like you have a good friend — replacing motor mounts isn’t a very pleasant job to do. Replacing the mounts requires the engine and transmission to be lifted and shifted around a bit in the engine compartment, which may have flexed an attached pipe, hose, or heat shield slightly out of position. During operation, especially under load, an engine wiggles around, perhaps an inch or more in several possible directions. This may be allowing one of the above parts to come into contact with the body or chassis structure, creating an annoying but probably harmless rattle. It’s also possible one of the replacement engine mounts may be of inaccurate shape, allowing contact between the engine and chassis mount brackets as the engine twists in its mounts during acceleration.

Another possibility is during the fluid-changing process, the power-steering fluid somehow wasn’t fully refilled. Should the power-steering pump gulp a little air due to low fluid level, a loud buzzing sound occurs, typically as the steering wheel is turned.

Why might the growling noise lessen with time? My hunch is that a flexed or slightly bent hose, pipe or heat shield may be relaxing towards its original shape and has moved further away from whatever it’s rubbing against. Damage could occur to a part that’s rubbing, depending on what the item is and what it’s rubbing against. You wouldn’t want an aluminum air conditioning pipe or fuel line to be chafing against something, as it may eventually wear through. For this reason it would be best to have the car looked over by your friend or a professional technician, after demonstrating the noise you are hearing.

Q: What’s your take on power steering flushing? I was just told I should do this at 48,600 miles, and I’d never heard of it.

—Jason Renner

A: There’s no question every automotive system can benefit from periodic fluid renewal, but there needs to be a balance between what’s good to do and remaining financially solvent. Power-steering fluid renewal is in my opinion, of less importance that renewing engine coolant, brake fluid and transmission fluid at approximately this mileage. Preventing corrosion of expensive engine and antilock brake parts and protecting your transmission from the effects of oxidized fluid — they can run $2,000 to $8,000 for replacement — is a higher priority to me than the typically trouble-free power-steering system.

If you have already addressed these other fluid needs and plan to keep the car for a long time, go for it. Another option is to renew most of the fluid yourself. Using a turkey baster — one that remains in the garage thereafter — suction out as much fluid as possible from the power steering fluid reservoir. Refill with new fluid, and drive a mile or more with turns in both directions. Repeat this procedure four or five times at your convenience, and you’ve likely displaced 75 percent of the old fluid. I’m not convinced “flushing” does more than exchange 90 percent to 100 percent of the fluid.