My BMW Loses Tire Pressure In the Cold
Q. Last winter, the tire pressure in my 2012 535xi BMW would decrease in the cold weather and the pressure light would come on and I would put air in the tire. This happened several times and is of course from the compression of the air. I took it to the dealer and they found nothing wrong. This year I replaced caps on the valves and it has not been a problem. Can valves leak and the cap be the fix?
A. Cold weather does have an effect on air pressure. The typical passenger car tire will lose about one pound of pressure for each 10 degree drop in air temperature. Regarding the valve stem cap, you are correct it is actually the cap that seals the air in the tire. The Schrader valve in the valve stem allow for easy inflation. Perhaps a combination of better sealing valve caps and better tire maintenance is keeping the tire pressure light off.
Q. Please tell me how it is possible to own a diesel powered car here in the northeast United States. I have tried this and I have found that all was well even with temperatures in single digits as long as the car was in the garage. However, if it was in the parking lot while I was at work, and the temperature dropped below 10 degrees, the car would not start. It seems to me that diesel vehicles are not suited to our climate.
A. I have road tested diesel cars in the worst of New England weather (no garage) and so far not had any problems. The biggest issue with diesel engines is fuel. There are two tests used on diesel fuel to measure its ability to flow in cold temperatures. Although generally diesel fuel is matched to temperature, not all stations sell the same fuel and this is where there can be a problem. If I owned a diesel powered vehicle I would certainly use an additive to minimize the chance of diesel fuel gelling.
Q. I have a 2007 Toyota Tacoma pickup truck that I purchased last November. The tire air pressure sensor light on the dashboard lit up, so, I put added air to all five tires and the light on the dashboard did not go out. I took the truck to a local tire store and they were able to turn the light off. All was fine until I hit a bump and the light on the dash came back on and has been on since. Are these tire pressure sensors necessary? With the light being on, does it affect anything? Can they be removed without affecting the computer? Is there a tool for adjustment? Are they expensive to replace?
A. The tire pressure (TPMS) sensors are required on most vehicles after 2007. Disabling the sensors or removing them is not advised. NHTSA issue a statement which essentially says disabling the TPMS system is illegal. The problem that I see, like your car the average life of the sensors is about seven years and 150,000 miles. The cost of new sensors can run as low at $23 to well over $100.
Q. I had a 2006 Toyota RAV4 that needed a new steering box or steering shaft replaced at about 65,000 mile. This $700 problem was fixed under an extended warranty. That RAV4 was totaled and I subsequently purchased a 2006 RAV4 with 68,000 miles on it. At about 75,000 miles I now have the same issue as I did with the old car. I took it to a Toyota dealership the quote to fix it was in the $700 range. My question is, has there been a recall or reported problem with this? I find it too coincidental that the same vehicles have the same problems.
A. There is a Toyota technical service bulletin about a fix for a clunk pop or knock-type noise when turning the steering wheel. The repair is replacement of the steering intermediate shaft. Although a common problem the fix is only covered by the three year/36,000 mile warranty.
Q. I have a 2012 Chevy 2500 extended van that I use for my business that I purchased new. Oil changes for the first 2 years are included at no cost. When I brought the truck in for an oil change at 3200 miles they told me that I didn’t need oil change because the oil percent gauge read 38%. I was told that it needed to be at 20% before they could honor the “free oil change included for 2 years’’. I always change my vehicle’s oil between 3000 and 4000 miles minimum as I was always told. Now I find myself driving more than 5000 miles before the percent gauge reaches 20% life. Confusing matters further the service tech adds 3000 miles to the oil change sticker which is placed on the windshield as a reminder. I am not comfortable waiting for 5000 miles before changing the oil. In your opinion, what is the correct procedure?
A. Here is what General Motors states: to help conserve oil while maintaining engine protection, many GM vehicles are equipped with the GM Oil Life System. This system can provide oil change intervals that exceed the traditional 3,000 mile (4,830 km) recommendation. The Dexos oil specification, with its requirements for improved oil robustness, compliments the GM Oil Life System by supporting extended oil change intervals over the lifetime of a vehicle. If all GM customers with GM Oil Life System equipped vehicles would use the system as intended, GM estimates that more than 100 million gallons of oil could be saved annually. Depending how you truck is driven (dusty roads, extreme temperatures and carrying heavy loads, I would follow the severe maintenance schedule which recommends oil changes every 3750 miles. This way if you got busy and went over that mileage there wouldn’t be any issues.
To comment, please create a screen name in your profile
To comment, please verify your email address
Conversation
This discussion has ended. Please join elsewhere on Boston.com