Slight knocking when cold
 

It's been fairly cold up here lately, 20-30 degrees.
My 92 has a knock for a while at startup until it gets up to normal water temp and normal oil temp. More pronounced while under load.
Oil pressure is normal and not fluctuating, about 70 psi.
Sounds like only one cylinder, not like the cold piston slap in my 5.3 Suburban.
Once everything is warmed up, the knock goes away. Gets quieter as the temps come up.
Car has 18,900 miles on it.
So, is this normal, or should I be checking rod bearings?

Re: Slight knocking when cold
 

There is a knock or noise of chain slap at start, in cold weather idling I have heard piston slap. Can ou get a video with the noise you are hearing?

Re: Slight knocking when cold
 

I'll try to get a sound bite this weekend, but with just a cell phone for video, I'm not sure it will be too helpful.....


I have no idea what LT5 chain slap sounds like.

Re: Slight knocking when cold
 

You only should hear it for about a minute or less on a cold start. Knock could be piston slap or the dual mass flywheel too

Re: Slight knocking when cold
 

This noise lasts a lot longer than a minute or two. More like 5 to 10 minutes.


I'll be pulling the pan either this weekend or next to replace the leaking gasket. I'll see if anything wiggles excessively while I'm in there....

Re: Slight knocking when cold
 

It may very well be the dual mass flywheel if the engine is running rougher at that temperature. Those temperatures can affect the coils, wires and injectors if they are marginal to begin with. This results in the engine running rough and imbalanced which in turn causes the dual mass flywheel to knock. That’s where I would look first. Bearing problems on LT5’s are very rare especially with those low miles. These engines are known to exhibit piston slap when cold however that should go away within a minute or two depending on the temperature. No reason to be too concerned at this point.
H
:cheers:

Re: Slight knocking when cold
 

You should try tightening the bolts on the oil pan a friend did and stop the oil leak on his Z

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Re: Slight knocking when cold
 

Bolts were tightened once already, still leaks. Also going to check the Oil Pressure Regulating Valve Cover Plate.