Question: I have a 2006 Nissan Frontier with a V-6 engine and 65,000 miles on its odometer. We use it as our second vehicle, mostly for driving around town.
The clutch, a replacement installed by my dealer less than 15,000 miles ago, already needs to be replaced, and I'm wondering why. Could it be because I park every day on my steeply graded driveway and keep the truck in place with a bad emergency brake?
Answer: I can't imagine the clutch slipping as the truck backed down the driveway. The clutch's pressure plate has more than enough pressure and engagement with the clutch disc and flywheel to handle and hold the engine's torque as you accelerate, so I really don't believe it would slip under the pressure and weight of the vehicle parked on a slope.
You didn't mention the clutch symptoms you are experiencing. If the clutch is slipping under normal acceleration, the problem is probably wear on the disc engagement surfaces. If the clutch shudders as you engage it, the issue is probably damaged or broken pressure plate springs or broken buffer spring in the clutch disc hub. I'd want to see the clutch components when they are replaced to determine what caused the problem - wear, broken pressure plate spring, damaged disc, or something else.
Q: I have a 2006 GMC Envoy Denali with 201,000 miles on the 5.3-liter engine. In the past six months, the low oil pressure light comes on at a cold start or even after the truck has been sitting a while. Once pressure goes up, the light goes off. A GM dealer said that they have not seen a case of a bad oil pump, so they suggested I replace the oil pressure switch on the back of the engine. I did this, but the problem still is there. Any ideas?
A: That's a lot of miles, for sure. Do you hear any engine noise or clatter on a cold start? Usually, if there's low oil pressure or poor oil flow at startup, you'll hear valve clatter or possibly a dull knock from engine bearings.
It's a bit unusual for oil pressure to be low on a cold start since its viscosity is at its highest when cold. But poor oil flow at startup would lead to low oil pressure symptoms. My first thought is that oil sludge is restricting oil flow through the oil pump screen at startup, delaying the buildup of oil pressure. My second thought is a leak between the oil pickup tube and the oil pump body, bleeding off oil pressure.
Check that the correct oil filter is fitted to the engine. Also, there is an oil pressure relief or bypass valve in the oil filter adapter. The wrong filter or a damaged or missing bypass valve could create these symptoms.
Q: My daughter just bought a 2009 VW Eos. The owner's manual and two mechanics say it must use premium gasoline. Why is that required with a four-cylinder engine?
A: It's not the number of cylinders, it's the fact that this engine is turbocharged. The higher heat and pressure in the combustion chambers mandates high-octane fuel that is more resistant to pre-ignition "pinging" or detonation.
We have a Passat equipped with the same engine and find no issues with using middle-octane fuel. That's what I would suggest for your daughter's car.
Paul Brand, author of "How to Repair Your Car," is an automotive troubleshooter, driving instructor and former race-car driver.