Some 2011 Town & Country and Grand Caravan minivans may produce a knock or rattle from underneath the vehicle with the engine running. According to Chrysler, the noise typically affects vehicles with 3.6-liter engines built before Dec. 22, 2010, and is most likely due to loose crankshaft-to-flexplate retaining bolts.
To make an accurate diagnosis, remove the transaxle and measure the torque on the flexplate bolts with a torque wrench. If the bolts read 70 ft.-lbs, this information doesn't apply; reinstall the transaxle and continue troubleshooting until the noise issue is resolved. If the bolt torque is significantly less than 70 foot-pounds remove the flex plate and install a revised flex plate (part No. 04800696AA), a new spacer (part No. 04752465AA) and eight new retaining bolts (part No. 06503465). To complete the fix, tighten the bolts by hand, torque in a crisscross pattern to 70 foot-pounds, then reinstall the transaxle.
The owner of a 2002-04 SC 430 model may come into your store complaining that his engine is idling roughly or is vibrating when the car is in gear at a traffic light. According to Lexus, the problem usually lessens when the vehicle is moving and the engine is put under a load, and is most likely the result of a prematurely worn engine mount stabilizer and/or engine mount insulator.
Start your troubleshooting by putting the car on a lift and performing a good visual inspection of both mounts. If you see cracks or tears in the rubber, replace both the stabilizer and insulator with upgraded parts (part No. 12381-50140 for the stabilizer; part No.12361-50151 for the insulator). Note that vehicles built on or after VIN JTHFN4#Y#40056830 already have the upgraded parts installed.
Some 2005-08 Xterra, Pathfinder and Frontier trucks with VQ40 V6 engines built before March 5, 2008, may produce a chirp or squeal from the engine compartment. Nissan reports that the noise usually surfaces at the first startup in the morning, especially in cold or damp weather, or after extended run times of one hour or longer. Drive belt slippage is the likely cause.
Start the repair by checking the alignment of the power steering pump pulley in relation to the other pulleys, readjusting the pump bracket, if required. If the pump pulley alignment is okay, replacing the drive belt and belt tensioner with updated parts should eliminate the noise issue. Order part No. 11720-EA200 for the new drive belt; part No. 11955-EA20A for the new tensioner.
"Factory Fixes" is written by Jim DePalma, a 30-year veteran of the auto repair business who has served stints as a service manager, parts manager and ASE-certified technician. His column provides vehicle manufacturers' authentic factory technical service bulletins (TSBs) that have been condensed for easier reading. Mr. DePalma advises that techs always check with a dealer or repair information system for the latest revisions before starting to work on a vehicle. He can be reached via e-mail at [email protected]