Dear Doctor: My 2007 Nissan Pathfinder has over 100,000 miles. I've noticed the SUV struggling to switch gears at 45 mph. I called to make an appointment at my local transmission shop, but they won't service it because of "all the talk about issues with this car" and suggested I go to the dealer for service. It is then that I learned that this Nissan is experiencing transmission issues due to radiator leaks. What can I do? -- Kathryn
Dear Kathryn: There is no question some Nissan SUVs have had radiator transmission cooler failure. When this happens antifreeze from the radiator enters the transmission ñ and the transmission will self destruct. You have a couple of options. The first is to replace the radiator. Second is to bypass the transmission cooler in the radiator and mount an external transmission cooler. I would also change the transmission fluid using the correct fluid. I have bypassed many radiator coolers. As a safety measure check the radiator coolant and transmission fluid. If either fluid looks like a milk shake then there is a problem. I have seen many transmissions survive this problem with a complete fluid flush.
Dear Doctor: I'm looking for something with high resale value, safety, reliability, performance, great gas mileage. I'm considering the Nissan Versa, Hyundai Accent, Mazda2 or the Kia Rio. Which of these four cars would you recommend? -- Brad
Dear Brad: I like the Nissan Versa and the Mazda2. This is not to imply there's anything wrong with the other 2 vehicles. The seats in the Versa were very supportive and it seems to be a good value for the money. The ultimate choice will be yours, of course. You can rent either car from a rental car company for a day or week to make sure you buy the right vehicle for you.
Dear Doctor: I recently had a brake job done on my 2010 Mazda5 at the local dealer. It was suggested that I also have the brake lines flushed and cleaned. This was the car's first brake job in three years with 66,000 miles. While I thought I was paying for a simple brake line bleed the cost was much more than I was originally lead to believe. I feel that I was guided into having an unnecessary service done at an additional cost of $150. What is your opinion? -- Don
Dear Don: We do brake jobs every week and I cannot remember the last time we flushed out a brake system, though there is no harm to performing this service as it will change the fluid and get out any impurities. The big question on up-sell services would be: is it needed? Does the owners manual say to perform the service? Next time ask if the service is a manufacturer recommendation.
Dear Doctor: I own a 1995 Ford F-150 with 142,000 miles. After just starting the engine and selecting the Drive gear the truck hesitates badly when I turn on the air conditioner. The problem doesn't happen when I turn the heat on. I replaced the cap, rotor, wires and plugs. Any ideas where I need to look? -- Ken
Dear Ken: The first step is to check the A/C compressor, making sure there is no abnormal drag when the clutch is engaged. Secondly, your 1995 truck may have an ALDL under-dash port connector. If so, then the technician will need to plug in a scan tool to check for all input information and sensor values. The tune-up parts you installed would have no effect on your problem. The truck could even have a lazy idle air control motor that's not compensating for the normal A/C drag.
Dear Doctor: I recently drove to Florida and returned North in March. While I was getting about 30 mpg in the southern states when I filled up in Pennsylvania my gas mileage immediately dropped to about 25-26 mpg and I also noted a slight decrease in power. Perhaps drivers that don't venture out of state do not realize this. What is being added to the fuel? Is it damaging to the engine and what purpose does it serve if it only makes you burn more fuel? -- CJ
Dear CJ: The cold weather fuel blend makes for easier starting in the North. Filling stations will convert to a summer blend when the weather heats up. The cold weather fuel blend ignites faster and emits lower emissions, which equals cleaner burning. The cleaner burning is not limited to just the emissions, we're also talking about valves, pistons, throttle body, EGR system and anything to do with the internal engine parts. All this comes at the cost of burning a bit more fuel per mile driven. -- Junior Damato, Motor Matters
Junior Damato is an ASE-certified Master Technician. Email questions to email@example.com. Mail questions to: Auto Doctor, 3 Court Circle, Lakeville, MA 02347