I'm trying to get as much research for this as I possibly can before taking action. Any info you guys could provide would be greatly appreciated!
My Situation:
Sometimes when I go to start my truck, I will turn the engine over and when it fires up there are a series of 4 knocks and then it goes away. Each and every time it does it, it's four knocks. It usually happens after the engine has been sitting for the night. I took my truck to a mechanic concerning this "knock". He said it sounded like front/rear main bearings or possibly the crank shaft, but he could not tell which area it came from. What puzzled him is that it only "knocked" four times and then went away. After that, everything sounded perfect. Absolutely NO ENGINE NOISE WHAT SO EVER. He commented that the truck ran remarkably well.
Info I recieved from another forum:
this is most likely a problem with the crankshaft main bearings. general motors had a bulletin on this when these engines were new and the fix was to measure the main bearings and install oversized bearings on the mains. they also note that this will not affect the longevity of the engine. bottom line is leave it alone.
Do you guys concur with this response?
Thank you for your input!
Phil