How To
John Paul, AAA Northeast’s Car Doctor, hears from a reader worried they may have waited a bit too long to have their car’s transmission fluid checked.
Q. A few years ago I bought a 2006 Mazda3 with 50,000 miles. It now has 66,000 miles. I had never checked the transmission fluid and recently had it checked. It was black. The garage drained it twice and refilled it. They said to come back in 10,000 miles and they would do a flush. There is plenty of talk online about the pros and cons of flushing transmission fluid. I wanted to get your opinion on this. Is the flush the way to go with a new filter or should I do a drain and refill with a new filter?
A. If the transmission is shifting correctly I would just do one more drain and refill. As odd as it sounds, the old seasoned fluid with some of the friction material held in suspension can help with shift quality. Now if there was a code, shifting issue, or contamination due to a leaking transmission oil cooler or an odd vibration, yes, flush the fluid and hope for the best.
Q. My daughter brought her 2019 Subaru Crosstrek to the dealership for an oil change and for a tire pressure light check. They came back with about $1,600 worth of work. I’m not questioning the integrity of the dealer but I was wondering if the pricing seemed okay or if she could get it done more cheaply somewhere else. She doesn’t have a regular mechanic as she’s always taken it to the place where she bought it. One of her TPMS sensors threw a code (twice) in the left rear tire, and they recommend replacing all four sensors for $890. Also the control arm bushings are cracking and wearing. They need to be done in the near future at a cost of $725. What do you think?
A. This issue with the control arm bushings is pretty common. In fact Subaru states that surface cracks are normal and don’t have any effect on ride or handling. Yes, in the future someday they will need replacing, but functionally they are fine. Regarding the tire pressure sensors, they are correct. If one or two are bad, the other two are not far behind. Depending on the labor rate, the price is pretty typical. At my virtual garage, where I use $165 per hour labor rate, with factory sensors the total would be $701. An independent shop or quality tire store could likely be less expensive, since they would be using aftermarket pressure sensors.
Q. I was a certified mechanic many years ago. I bring my vehicles in for service either to the dealer or a local mechanic. At my truck’s last oil change my mechanic noticed the anti-freeze reservoir was a little low on my 2018 GMC Denali 1500 pickup. He asked if I checked and I admitted I hadn’t. It has 75,000 miles on it. The temperature gauge reads fine and I see no leaks or puddles under the truck. I just added another inch or two to the reservoir. Can the antifreeze evaporate or is there something that is going on?
A. Could there be a leak? Maybe, but antifreeze is half water, and water evaporates even in a closed system. At this point, I would do just what you did, top it off and check it periodically. If you start adding coolant more often, have the system pressure checked. The common leaks are the plastic connection to the heater core and plastic radiator tank. On some of these engines, the cylinder head is porous and can leak at the outer head bolt boss on the cylinder head. You can usually see it and smell it. If you are not smelling coolant, probably just maintenance (or lack of it).
Q. I have a 2015 Kia Optima, which has currently 60,000 miles. The car has been maintained and is in like-new condition. I have been concerned about the procedure on cleaning the valves. What are your thoughts on the process, and should I have the dealer handle it?
A. The combustion chamber (valves, pistons) can be cleaned with chemicals using a special tool that adds a concentrated cleaning solution to the engine. In more extreme carbon issues, the engine is partially disassembled and cleaned with a sandblaster like device that uses walnut shells. The walnut shells clean the carbon without damaging the engine. At this point if the engine is running well, I would use TopTier fuel and periodically use a quality fuel additive that cleans fuel injectors and the combustion chamber.
Q. Next month I will have owned my 2025 V6-powered RAM pickup truck for a full year. The check engine light comes on from time to time. The dealer tells me Chrysler has yet to figure this out in a small percentage of like vehicles. Any thoughts on this?
A. There have been some issues with code generated for random engine misfires. I suspect that this is an issue that will eventually be fixed with a software update, rather than mechanical repairs. The bulletin that I read stated engineering is looking into the issue. I would keep working with the dealer to find a solution. Also, keep a log when the light comes on, noting fuel level, engine temperature, and speeds driven. This logbook may help with finding a solution.
John Paul is AAA Northeast’s Car Doctor. He has over 40 years of experience in the automotive business and is an ASE-certified master technician. E-mail your Car Doctor question to [email protected]. Listen to the Car Doctor podcast at johnfpaul.podbean.com.
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