Re: Engine Knock Right at Engine Start only!!

"Dunamis" <u43397@[EMAIL PROTECTED]
> wrote in message news:83af08b03e6ec@[EMAIL PROTECTED]
> 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
>

It is simply the hydraulic lifters pumping back up after leaking down 
overnight.  Engines have been doing this ever since hydraulic lifters were

invented.  There is nothing wrong, they are working like they are supposed

to.   See http://en.wikipedia.org/wiki/Hydraulic_lifters
 if you don't 
understand.

Randal