Check to be sure all rocker-arm bolts are tight

Q I own a '99 Chevy Lumina with a 3.1-liter V6. This weekend I got a flashing check-engine light with a severe misfire. I took the vehicle to a shop, which told me I had two rocker arms blown right out of the head, and two more were working their way loose. The mechanic was able to get them back in, and the car is running fine now.

Why would this happen? This is the second time that this has happened to this vehicle, but not to the same rocker arm as the first time.

A The rocker arms that actuate the valves in this engine pivot on a special bolt that is threaded into the cylinder head. From your description, it sounds as if the bolts worked loose over time until several of them backed all the way out, causing the rocker arms to pop free of the pushrod and valve stem. My Alldata automotive database pulled up GM service bulletin 02-06-01-034 updating the tightening specifications for the rocker-arm bolts. The bolts should be tightened with a torque wrench to 124 inch-pounds, then tightened an additional 30 degrees of clockwise rotation. The valve lifters are hydraulic, so no adjustment beyond this tightening specification is necessary.

The most likely cause for the loose rocker arm bolts in your engine is either inadequate tightening originally, or an effort to adjust the rocker arms at some point in the engine's life. The only other possible explanation I can think of is some type of mechanical interference. The two possible causes for this would be a significant carbon buildup on the face of the valve or top of the piston, causing physical contact between the two, or wear, erosion and/or excess heat causing the valve seat to sink into the cylinder head. This could progressively remove the clearance between valve/rocker/pushrod/valve lifter, causing a mechanical binding action that might work the rocker bolt loose.

At this point, the problem has been repaired for the rocker arms that came loose. I'd suggest making sure that all 12 rocker bolts are properly tightened to the updated specs.

Q I have a 1997 Jeep Grand Cherokee with a V8 engine and 160,000 miles. It has an extended crank time when starting. A repair shop says I need a new fuel pump because it's wearing out and taking a long time to get gas from the tank to the engine. It's a $750 repair. The vehicle has had this "extended crank" problem at least two years. How long can the fuel pump last before it completely goes out?

A Until the absolutely most inconvenient moment for it to fail and leave you stranded -- isn't that always the case? Your Jeep's problem is more likely the check valve in the fuel pump assembly than the pump itself. This valve is designed to keep fuel from draining back into the tank, resulting in a loss of fuel pressure and extended crank time. Try turning the key to the "run" position for two seconds, then off. Repeat this priming action a half-dozen times before you actually engage the starter motor. If that helps the engine start faster, you've found the temporary fix. But ultimately, the entire fuel pump assembly in the fuel tank will need replacement.

A I'm assuming the axle "seal" leak is from the right front drive axle. This is typically the result of a split in the flexible rubber, bellows-style boot that seals and protects the outboard constant-velocity (CV) joint. Once the boot splits, the grease sprays out and dirt, grit and road debris get into the joint. This accelerates the wear in the joint, leading to a clicking sound as you initially accelerate and turn at the same time. When this noise starts, you still have some time before a complete failure, but eventually the CV and boot -- or the entire axle assembly -- will need replacement.

Because of the attractive price of remanufactured drive-axle assemblies -- with new CV joints and boots on both ends of the axle -- I prefer to replace the entire assembly rather than just the outboard CV and boot.