piston slap

100R1 · June 10, 2003

If one is looking at a used truck 2001 - 2003 with the 5.3 or 4.8 how can you tell if there is a piston slap problem?

does it happen only when the engine is cold and first started up and does it disappear as the engine warms up?

What does piston slap sound like?

valve tap, rod knock, Diesel idle sound?

what should I look (listen) for and when?

Shaners · June 11, 2003

You'll hear a knock on a cold start, and it will go away in about 30 seconds or so...

jhm · June 11, 2003

Here is what my 4.8l does: It has no cold start knock, but close the windows, turn off the radio and accelerate moderately hard and you hear the rattling high frequency noise. Dealer told me this is also piston slap.

Huntaholic · June 11, 2003

Here is what my 4.8l does: It has no cold start knock, but close the windows, turn off the radio and accelerate moderately hard and you hear the rattling high frequency noise. Dealer told me this is also piston slap.

could be, but that sounds more like spark knock, or predetonation to me.

jhm · June 12, 2003

Yea, I thought it was preignition too. Even the dealer thought so. After testing the entire engine on the analyzer and replacing both knock sensors, decarbonizing the engine and putting it on the analyzer again, the noise is still there. They called GM for help and were told it was a sign of piston slap. They then told the dealer it was normal and I had to live with it. This is when I got real pis**d and they ended up giving me a 6yr/100k extended warranty on the entire engine, every single part on it, which is also transferrable.

Huntaholic · June 12, 2003

Yea, I thought it was preignition too. Even the dealer thought so. After testing the entire engine on the analyzer and replacing both knock sensors, decarbonizing the engine and putting it on the analyzer again, the noise is still there. They called GM for help and were told it was a sign of piston slap. They then told the dealer it was normal and I had to live with it. This is when I got real pis**d and they ended up giving me a 6yr/100k extended warranty on the entire engine, every single part on it, which is also transferrable.

That sounds fair, drive it like you stole it then!!

DaveD · June 13, 2003

I have the same problem. But at 30,000 miles it lasts a lot longer (5 minutes) and I can still hear it a little after a 20 minute drive to work. That's when its 75 degrees outside too.

Read that extended warranty carefully it is really for 3 more years (my date is 3 years beyond the date of the letter) or 100,000 miles whatever comes first. Mine's good till may 2003

I would be very careful buying a used vehicle that might have this problem. I'd like to sell mine or trade it but the problem is too well known and I wouldn't stick a private individual with it although I could probably figure out how to mask the problem for short drives.

Be darn sure the engine is ice cold on anyone you look at. If you can touch the engine, or radiator fluid and its the same as the outside ir temperature I'd tell the owner I'll be back when its cold first thing in the morning and don't start it at all till I get here.

jhm · June 13, 2003

All extended warranties start at the expiration of the original warranty. Even the ones you can buy such as the ones advertised on Edmunds. On those, even though you pay for it now, you cant use it until the original expires. In the mean time the clock on the one you just purchased is also ticking! The one GM "gave" me expires in Jan 2007 or 100k, whichever comes first. This whole piston slap thing really sucks and the really stupid thing is they shortened the piston skirts to reduce mass and thereby get more mpg. I only get 15mpg mostly on short trips, I hate to think what the gas mileage would be if they used conventional length piston skirts!

dukbludvl · June 13, 2003

I saw the post here on possible spark knock and wonder if you all can help me. I recently (at 45K miles) changed my spark plugs to champion copper plus and almost immediately I noticed a consistent ticking sound (best heard when you are at a stop and the windows open or if you're outside the truck listeining to it idle). Could this be spark knock? Could it be the result of something I did with the spark plug install?

Please advise me and let me know if a new set of plugs can fix it or what I need to do. The truck purred like a kitten even at idle before I installed the new plugs.

Thanks! Oh yeah, 00 Yukon 2wd 5.3L with 51K miles now.