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knock at startup

Jakegday

Jakegday

New member
hello. whenever i go to start my car you hear what sounds like the rods knock for a little less then a second. this does not happen if ive started my car within the last hour or 2. if i let it sit a few hours it will do it just a little bit, but if i let it sit overnight it does it the worst. at its worse it is still less then a full second.

is this normal for these engines? is there anything i could do to fix/improve this?
 


Mine makes a little extra noise when it's really cold out (below freezing) on cold starts. Goes away quickly. It's probably piston slap, which is the piston being slightly smaller than usual due to the cold (contraction) and it makes a little chatter between the cylinder walls until it warms up to fill the space again. GM says it's normal on all their engines.

Some engines are worse than others. The 60* V6s (3100, 3400, 3500, 3900) will have piston slap year round on cold starts.
 
Could be your oil also. With it being cold out, the oil will be thicker and could take just a little longer to pump htrough. Never really heard it happening unless the oil pump is going out, but just a idea. If the oil is to thick for the temps may cause it too.
 


i get that too, mine sounds like the Traction Control "can" rattle when i start it up, runs perfect other wise, sometimes it does it some times it dont,
 
Hey i got a 02 gp GT and i have somewhat of the same problem when it is cold out. When i start it up it makes a really aggressive knock then it turns into something that sounds almost like a manifold leak. Anyone ever experienced this before with the 3.8?
 
This may seem like it's off the wall, but what oil filter are you using? A bad anti-drainback valve will let the oil drain/siphon back into the oil pan, taking a second for the system to refill after you start the car.
 


This is normal. The oil has not hit the lifters and it is just clicking for a minute. nothing to worry about. I have had alot of customer complaints at work and gm says it is normal. cylinder number 2 exhaust lifter is the one that is clicking. just let it be.
 
Also if it is cold outside the bypass valve on the oil filter goes by and fills them up faster. This also may be a reason
 
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