Oil-pressure warning can be tricky to diagnose
Question: My 2003 BMW 325Ci has 157,000 kilometres on it and generally drives perfectly. I have always taken good care of it. However, after about 10 minutes of stop-and-go traffic, the oil pressure light starts flickering.
I know the problem isn’t the oil level because I always check it every 1,000 kilometres and do timely filter changes. The warning light goes away the moment rpms are above 600.
I Googled the issue and found four possible root causes: bad sensor, engine pressure leak, bad oil pump or dirty idle control valve. What would you advise?
By the way, I always use 10w30 synthetic Mobil 1 oil. G.B.
Answer: Your oil pressure warning light likely illuminates when pressure drops to a reading of 8 pounds or less. I wasn’t able to find the exact figure. Under normal or hot conditions, idle oil pressure should be in the 10-15 pound range and should increase with engine speed.
Among the possible reasons your warning light might be illuminating during hot idle conditions are: thin or contaminated oil, low idle speed, an off-calibration oil pressure switch and low oil pressure due to excessive bearing clearance or a worn oil pump.
Let’s start with recently changed, contaminant-free oil and correct idle speed. BMW specs call for 650-750 rpm, so you seem to be idling a bit slow, possibly due to a dirty throttle or faulty idle control device. I’m thinking this is your only concern.
Actual oil pressure can be verified by removing the oil pressure sending unit and temporarily attaching a mechanical gauge. Removing the idle control device and cleaning it, along with the throttle bore, might just do the trick. There are several YouTube videos illustrating the procedure.
Q: My 2015 Ford Edge SEL is quite noisy. The noise comes from the cargo area and becomes softer or louder depending on the road surface. It’s particularly bad on interstate highways.
After a frustrating and noisy year of cruising, I beg you for advice on reducing this annoying sound. Do you know of a noisereducing undercoating? How about a sound-deadening material to put on the inside of the car?
H.W. A: Try cleaning the front and rear wheel wells and applying several coats of Rust-Oleum rubberized undercoating or a similar product. Be sure to wear eye protection.
Further coating of the Edge underside would also be helpful but this would be tough to do at home. Perhaps a quick-lube place could apply it for you for a modest fee. Another angle is to apply some Dynamat or similar material to the inside wheel wells and load floor area. This is a thin rubberized sheet material that really knocks down sound. Removing and reinstalling interior trim and carpeting would be needed. Both products are available at auto parts stores and on Amazon.
Also, some all-season tires are noisier than others. Try researching noise levels at TireRack.com when it’s time for replacements.
Q: I recently heard that batteries are the most frequently replaced component in cars that are three years old. Any idea what might be the cause here? Might this have anything to do with the proliferation of automatic startstop systems to save fuel? Or the “vampire” effect of trickle-powering electronics to preserve settings, etc.? Or are automakers just using cheaper batteries? J.G.
A: Carmakers would not benefit from installing crappy batteries. More likely, batteries are not getting adequately charged when driving. The vampire effect from infotainment and other power hogs contribute to key-off drains. This is particularly an issue when drivers leave their remote keyless entry fob in the car. Plus, telemetry during down time (electronic control module updates, maintenance data, etc.) taps power and is most harmful to already-undercharged batteries. A battery that is chronically undercharged will develop a condition called acid stratification where stronger acid settles to the bottom with weaker acid near the top. It shortens the battery’s life.