Q: I have a 2006 Nissan Frontier, straight stick V-6 with 65,000 miles. The pickup is used as our second vehicle, driving mostly around town. I need a new clutch, the second one in 15,000 miles. No oil leak was detected by my mechanic. Is the reason that a new dealer-installed clutch went out within 15,000 miles because I parked daily on a steep hill, with a bad emergency brake? I park my pickup in my driveway which has about an 8- to 10-degree slope. I pull the truck up the slope, put on the emergency brake and put the transmission in reverse. The emergency brake alone did not stop the truck from backing down the driveway. I had the emergency brake system repaired about a month before the clutch went out. What do you think? Is parking on a hill with a bad emergency brake bad for the clutch?
A: I can't imagine the clutch slipping as the truck backed down the driveway. With the transmission in reverse I would think the clutch would stay engaged and turn the crankshaft as the vehicle moved backward. 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 now experiencing. If the clutch is now slipping under normal acceleration, the problem is usually wear on the disc engagement surfaces. If the clutch now shudders as you engage it, the issue is usually 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 engine. In the past six months the low oil pressure light comes on at a cold start or even after it 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 is the author of "How to Repair Your Car" and "How to Repair Your Truck and SUV," published by Motorbooks.