Loud Knocking noise when trying to start truck!!!!

[Justin Steele]

i have a loud knocking noise when trying to start truck happens from time to time i think it is the flexplate but i am not sure.. i hear no rattling or anything when it is running need some answers quick. 2000 chevorlet s-10 v6/4.3!!!!

Topic

[Mason]

Piston slap maybe?

[Justin Steele]

i dont think its that its only on start up

[619DioFan]

Remove the lower cover so you can access the torque convertor. grab the convertor and try to turn it by hand. have someone watch the lower crank pulley . if you can turn the convertor either way slightly and get no movement from the lower crank pulley then you have a prob with the flex plate. they crack around the bolt holes were it mounts to the back of the crank shaft. as you twist the convertor you may here a cracking sound from that area as well. this sometimes sounds like a rod bearing going out.

[EricTheCarGuy]

It could be a lot of things if I’m honest. I cover many of them in this article.

http://www.ericthecarguy.com/faq/diagnosing-noises-in-your-car

Good luck and keep us posted.

[Ryan Wofford]

Maybe loose starter bolts?

[Lorrin Barth]

Missing tooth on the ring gear? If this is the case, one day when the engine stops just right, when you go to start it, only the starter will spin.

[Ingvar]

[quote=”Steelflex21″ post=128578]i dont think its that its only on start up[/quote]

That’s exactly when piston slap occurs. Cold start ups. Goes away in about 15-40 seconds. Google GM engine piston slap, have fun. Hundreds of pages.
Otherwise, sticky lifters. pour can of Seafom through oil for about a week worth of driving, drain, pour some cheapest oil in your weight in, drive on it for about 20 miles, drain and refill with good oil.
Be happy.

[Author]

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