Q: I had my 2012 Impala LTZ in the shop for a noise. The rear struts were replaced along with front rotors and pads. The brake job was supposed to take care of the noise up front. I can still hear the noise up front occasionally. I hear it only when it sits for a while in the parking lot and when I start it, put it in drive and move away slowly turning the wheel to the left. It sounds like a scraping noise and it only lasts for about two seconds. I don't hear it when I turn the wheel to the right or when I'm driving and turning corners. The dealer said the noise in front was from rust on the inboard side of rotors. I have about 41,000 miles on the car. What do you think it could be?
A: Since the front pads and rotors are new it's unlikely the noise is being generated by rust on the inboard surface of the rotors. That said, GM suggests "burnishing" or bedding the new pads by making a half-dozen or so firm brake applications from 45 mph to about 10 mph with some cooling time between applications. GM has developed a new process in the manufacture of brake rotors that hardens the surface to reduce corrosion, wear and thickness variations.
The noise could also come from a stuck brake caliper piston or slider. Perhaps as you initially turn to the left the very slight flexing of the stub axle or hub might cause an initial contact between the pad and rotor.
Another possibility is the loss of pre-load on the front hub/bearing assemblies. Have the front hub nuts re-torqued to 162 ft. lbs. to see if the noise stops. If it does, have new hub nuts installed.
Q: I have a 2007 DTS Cadillac purchased in 2011 with 81,000 miles on it. It has started leaking oil from the oil pan. I took the car back to the dealership but they told me no oil was leaking. I brought the car to my son-in-law, who is an oil change technician, and he said the oil pan was leaking oil. Is there a recall on the DTS from 2001-2007 for this? Please advise.
A: No recall, but my ALLDATA automotive database did locate GM service bulletin #03-06-01-027A dated May 2008 that addresses the issue of lower end oil leaks. It describes a new procedure for re-sealing the oil pan using a specific RTV sealant. It's a very involved — read "expensive" — repair requiring removal of the engine and transmission.
The bulletin indicates this would be covered by warranty during the original warranty period. Although it never hurts to ask, it would not appear that warranty coverage would apply on this eight-year old vehicle.
Personally, I wouldn't do anything until the leak is severe enough to require you to check the oil level every few days to prevent running low on oil. Old cardboard placed under the car in the garage will catch most of the dripping oil.
Motoring note: From Frank, no last name: "I am writing concerning your response to a question concerning a 2002 Buick Century with no gear position or mileage display. This is a very common problem in Buicks from 1996 to 2002. I have personally repaired these issues in both my wife's and son's Centurys. The problem is poor soldering of the four 150-ohm resistors in the instrument cluster. Just remove the dash, remove the instrument cluster, then remove the cluster cover. The resistors are mounted above each other in a parallel column. Solder the new ones in and put it back together. Total cost of $1.29 at Radio Shack for the resistors.
The perfect example of the automotive KISS principle — a willingness to try the simple things first. Thanks for taking the time to share this, Frank, we all appreciate it.