Clunking Sound in Steering Column is Shaft Failure

March 12, 2011/Steve Tackett

MOTOR MATTERS ASK THE AUTO DOCTOR BY JUNIOR DAMATO

Dear Doctor: I own a 2003 GMC Sierra 1500 pickup and now have a clunking sound in the steering column. A mechanic said the sound is where the column goes into the gearbox. There was a recall, but I never got notification. I understand that even some of the vehicles repaired under the recall still have the problem. Do you have the solution? Robert
Dear Robert: An ongoing problem on this model-year truck has been the lower steering shaft failure. GM had a grease repacking kit for a while and now an updated lower steering shaft. I have replaced a number of these steering shafts over the years. As for any recalls, check the dealer service department with your VIN number. I can say that your vehicle will feel like new once the shaft is replaced.
Dear Doctor: My 2000 Mercury Grand Marquis was in a flash flood and a wave of water passed over the hood. After riding a short distance (2 blocks) my engine started to knock. I was 10 blocks from home, so I drove home and put the car in the driveway. My mechanic came over and towed the car to his shop. After checking it out, he found a piston was bent and he replaced it. Even since, the car runs as though the engine is missing when it’s idling at traffic lights. If I put the engine in neutral the roughness stops. Hope you can help. I love the car! Ray
Dear Ray: The roughness at idle speed indicates the engine is not firing completely on all cylinders. A weak cylinder vacuum leak or other worn component can cause a rough idle. Have the technician perform a cylinder balance test. Using a professional scan tool (in mode 6), the technician should be able to look deep into the computer for information. A weak sealing valve will also cause a rough idle.
Dear Doctor: My 2003 Ford Explorer has an intermittent thumping noise coming from the suspension or drive chain. It is perplexing because it only happens when the vehicle is warm. During the recent subfreezing temperatures, I could drive all day without hearing the loud thumping. Once the temperature is above 40 degrees F, it thumps. The dealer replaced the rear hubs, but that didn’t resolve the problem. I was also told it was road noise that I was hearing. It is clearly not road noise. Do you have any ideas that I might suggest to my mechanic? Jonathan
Dear Jonathan: If I were servicing your truck I would first want to know whether thump happens when your foot is on the brake, gas or just coasting.

2000 Mercury Grand Marquis

Does the thump sound get slower or faster with speed? Take the vehicle to an independent shop or to a technician who can take the time find the source of the problem.
Dear Doctor: I am the original owner of a 2002 Chevy Monte Carlo SS with just 48,000 miles. The car runs fine at low speeds, but when hitting the passing gear, the engine misses and almost chokes out. When in neutral and revving the engine to 4,000 rpm, the same thing happens. I got trouble code “low air flow,” so I changed the air filter, fuel filter, and cleaned the MAF sensor. Any other suggestions? Mike
Dear Mike: The technician will need to hook up a fuel pressure tester and scan tool and monitor both while on the road test. A common failure with this car is a partly blocked catalytic converter. The technician will remove the oxygen sensor in front of the catalytic converter and measure the backpressure. Any backpressure reading above 1.5 pounds when the engine is raced to 3,000 rpm is too much and usually indicates a restricted exhaust. Do not use a cheap aftermarket replacement catalytic converter. Use either a factory GM replacement or direct fit Walker brand.
Dear Doctor: I am interested in the new 2011 Chevrolet Cruze with the automatic transmission. I know this is the first model-year of the Cruze, and GM does not have a good track record on building small cars. What are your thoughts on the new Cruze? Matt
Dear Matt: I spent a week in a new Chevy Cruze with the 1.4-liter, 4-cylinder engine and 6-speed automatic. Our test car’s base price was $18,000 and the as-tested price was $21,455 with optional equipment. The engine and transmission provided smooth and ample power at all speeds. Gas miles are a big plus at 26 mpg city, 37 mpg highway. Interior quality was beyond my expeditions. I have no problem recommending the new 2011 Cruze as a good vehicle to take out for a test-drive. — Junior Damato, Motor Matters

Junior Damato is an ASE-certified Master Technician.

E-mail questions to info@motormatters.biz

Copyright, AutoWriters Associates, Inc., 2011