Expert: Van - 12/15/2005

Question
I have a Chev 2003 Suburban.  It has a noise on the left side of the engine (looking from the front).  It sounds somewhat like a belt slipping or it could possibly be a spark knock.  I am not sure what it is.   It seems to do it worse in cold weather and it does not do it all the time.  I did notice that the oil pressure gauge is slightly below 40 at idle.  I have a Chev 2002 PU and at idle the oil pressure is higher.  Any suggestions.  Thanks for your help  

Answer
Hi Todd,
First, remove the serpentine belt, and then start the truck without it, to see if it is something belt driven. A bent pulley, or a bad tensioner can knock like that.
If it is still there, reinstall the belt, and then get either a mechanics stethescope, or a long screwdriver, and hold it against your ear, and with the engine running, prod around and see if you can narrow it down.
If it is toward the rear of the engine, it could be the torque converter bolts loose on the flex plate.
If you think it is down inside the engine, I would remove the inspection cover for the flywheel, and with the serp belt removed, pry the crankshaft toward the front, and then toward the rear, to see if there is excess play. It shouldn't move more than just a fraction of an inch. If it does, the thrust bearing may be worn out, but I have seen soft crankshaft journals wear, and allow the shaft to move, where it bumps the main bearing journals.

But that would be more of a "thunk", or a knock.
Your pinging may be from the a/c compressor clutch or bearing, or an idler pulley.

Van