1995 Chevy Silverado Quick Engine Knock at start up.

Tiny
DUNAMIS
  • MEMBER
  • 1995 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 203,000 MILES
This is an intermittent problem. 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". I explained to him that it sounded like a lifter to me. I started up the truck to see if it would actually knock for him and did. He got this puzzled look on his face. He said that it didn't sound like a lifter to him. He said it sounded like front/rear main bearings or possibly the crank shaft, but he could 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.
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Sunday, May 4th, 2008 AT 2:32 PM

4 Replies

Tiny
MASTERTECHTIM
  • MEMBER
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.
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Sunday, May 4th, 2008 AT 2:35 PM
Tiny
THE FACTORY MAN
  • MEMBER
IF I AM RECALLING THIS CORRECTLY, I think the TSB from GM brought into question the clearance of the front main bearing. I THINK part of the diagnosis was to remove the serpentine belt and if the noise then was less or went away that confirmed the main bearing issue. I can not access the bulletin right now but I think the fix was to install a.0005" larger bottom main bearing shell. I also think the bulletin stated that the noise would not affect the long term durability of the engine but was mainly a customer concern issue. If this is what you are dealing with I would leave it alone as MASTERTECH TIM says.
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Saturday, May 10th, 2008 AT 12:06 PM
Tiny
DUNAMIS
  • MEMBER
Someone told me to removed the serpentine belt and turn the engine over toy listen for the knock. The only problem with that is that my engine doesn't knock all the time.

I am eventually going to build an engine to put in my truck. I think I may buy one from a junk yard or something and put it I the garage to tiner with. The only thing I need to know is what spec's the engine has to be in order for it to fit in my truck.
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Saturday, May 10th, 2008 AT 12:17 PM
Tiny
THE FACTORY MAN
  • MEMBER
Remove the belt and start the engine and listen for a knock. I assume this happens on a cold start after the engine sits over night. Don't run the engine very long with the belt off. I'm not sure what you are asking about as far as specs for a replacement engine. Keep it simple and get the same engine from a wrecking yard.
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Saturday, May 10th, 2008 AT 12:29 PM

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