cold & warm engine start knock

[rchjr]

hello i have a 03 monty with the 3.4 i have been noticeing a loud knock when i start it when it is cold or about 2to 3 hours after i shut it off even when the engine is still warm it only last for about 30 seconds or so. i've checked and i am not loosing oil . coolent it still in proper range check it every day not sure what this could be i have heard about the famous intake gaskets. but i dont seem to be loosing fluids sounds like it is comeing form near cylender 6 . any help or suggestoins would be greatly apreciated

[bobss396]

It might be a piston slap. The piston is out of round until it warms up a bit and the noise goes away. Rod noises do not go away. If you know a mechanic, have him look the problem up on All Data or Mitchell, if he uses one of their systems.

Bob

[Rally Sport]

Yeah sounds like piston slap.. do you run synthetic oil in the engine? If you do, go back to regular oil.

[rchjr]

yes i am using synthetic . i had a tecnition look at it he seems to think it is oil drain back from the filter so i will cange the oil with regular insted of sythetic and try a better oil filter with a anti drainback vale and go from there thanks for you help

[bobss396]

That might be the answer. Synthetic oil's viscosity reamains the same throughout the range of temperature. Regular oil just might coat things for a matter of seconds until the piston skirt gets itself adjusted.

But do look for service bulletins on the piston slap issue, Mitchell or All Data are good places to look if you know someone that owns a shop and has either service.

I had a 350 in a Chevy truck that had a cold piston slap in it. I just kept on top of the oil changes and drove it all over the place for a few years until I sold it.

Bob