Rattling sound

[Pomorza]

Hello guys.

I did an oil change in my Z. Decided to give 20w50(VR1) weight oil a try as the temps here in Tucson are getting a bit warmer. Went to the local store bought six quarts of oil (one spare) and a Bosch oil filter. Put everything together added 5 quarts oil and away I went.

 

When I rev the car up now to about 4k and let the throttle go it will make this rather annoying rattling sound from the valve cover for a few seconds. Any ideas? Is the oil just too thick to lubricate the cam at idle. The pressure is sitting exactly where it needs to. I pulled the fill plug out and the cam is most definitely covered in oil. The sound was not present this morning when I drove to school or before I did said oil change.

 

So I thought it was the timing chain. Spent last week taking the car apart and replacing the cam gears chain, tensioner, spring, and guides. Well sadly replacing the timing chain did not fix said sound. I'm not saying it wasn't needed as the old chain was about an inch longer than the new one and the tensioner spring was roughly a third of the size of the new one, so it wasn't all a waste. Atop that the cam was off time and there was about an inch of sludge in the oil pan, so it was most definitely needed.

 

Anyhow the sound has now become more localized from when it first appeared. For what I can determine (and my mechanic I go to) the sound appears to be coming from the mid to rear section of the valve cover.

 

Before I go further this is what occurs. The sound only appears between 1 and 2K on the tachometer. Only does it on deceleration (not on acceleration) it doesn't really vary with pitch or frequency even if I go up to 5k and release the throttle, it seems to be rather constant and only occurs at said specified ranges. It also only occurs when the engine is hot. When it is bone cold it sounds prefect.

 

My mechanic suggested that maybe one of the rocker arms in the motor is wobbling or moving when decelerating (that is load being taken off). Any ideas guys? This is rather annoying.

 

 

Thanks

Jan

Edited March 23, 2010 by Pomorza

[Heathhh]

I suggest checking valve clearances and while your in there check the rocker assemblies as well then too. If your lucky it could just be those are the issue. Possibly something fell into the crankcase while you blinked? Or you could sea foam it and then do another oil change and see if that cures it Could be some sludge in the rocker assemblies.

[Pomorza]

I suggest checking valve clearances and while your in there check the rocker assemblies as well then too. If your lucky it could just be those are the issue. Possibly something fell into the crankcase while you blinked? Or you could sea foam it and then do another oil change and see if that cures it Could be some sludge in the rocker assemblies.

 

I seafoamed it Z before I replaced the timing chain as I did the oil pan gasket at the same time. I'm going to check the clearances as soon as I can. I did them already about two week before I did the timing chain with no luck.

 

Thanks for the ideas

Jan

[MONGO510]

If you find that one of the valves is very tight, then check the retainer for wear. When the retainer is failing it will be noisy and the clearance will be tight at the same time. The method for checking a bad retainer is to remove the lash pad and inspect the bottom of it. The only surface that should be shiny from wear is the center depressed section. If the outer ring section is shiny then you have a bad retainer and it and the keepers should be replaced.

 

Mongo