Knocking sound when starting...loudest when engine is cold

**jlbpa** · 02-08-2009, 11:14 AM

2001 k1500 5.3 with 104,000 miles. Started several months ago when engine was started but would get quiet after 10 or 20 seconds. Now it knocks longer and louder but does eventually get quiet. Sounds louder than a lifter. I'm wondering if a piston. I bought the truck about 4 or 5 years when it had 56 thousand on it. Truck looked new when I bought it and did not notice and problems with engine. Since then it has gotten fresh oil every 3000-4000 thousand. Most of my miles are highway. And from the look of the truck I'd guess most of the previous owners mileage where highway.

I'm bummed!!

**ibmoses** · 02-08-2009, 11:50 AM

What oil are you using?

Sounds like piston slap.

Bert

**dwill3015** · 02-08-2009, 12:41 PM

Welcome to the site! Check out THIS SITE for more info on piston slap.

**hunter541** · 02-08-2009, 12:51 PM

this is commen in colder weather on silverado's i never seen these blow up what gm was doing was removing all the spark plugs and putting in top engine cleaner [nasty stuff ] leave in over night,crank it over with no plugs reinstall plugs.it takes some time to get started because it washes the cylinders down,it will smoke like crazy and then change oil to mobil 1 they clame that it carbon build up hope this helps

**jlbpa** · 02-08-2009, 01:41 PM

I have used pennzoil or castrol.

I'll contact the local gm dealer and tell them I think I have excessive piston slap and see if they come up with the carbon buildup remover solution.

**plumber_rob** · 02-08-2009, 02:06 PM

My 2000 Silverado has the knocking sound when I first start it up in the morning. It has a 108k on it and the knock doesn't last too long. I was told that the early 5.3's were build very loose on the clearances. After reading the site that Darcy posted above it must be true.

**jlsparky7** · 02-10-2009, 09:18 PM

Try some seafoam. Stuff works great for cleaning out carbon build up.

**zachh1020** · 02-10-2009, 09:59 PM

Classic case of the Infamous Chevy Piston Slap. Plaguing Chevrolet owners across the nation.

**JMoney02** · 02-12-2009, 11:31 AM

Darcy, where do you come up with these sites, man your amazing with some of these......It even has been back in the late '70's, but just not as noticable.....

Jeff

**Dr_Zero** · 02-12-2009, 01:00 PM

Originally Posted by jlsparky7

Try some seafoam. Stuff works great for cleaning out carbon build up.

Would definitely try Seafoaming the intake it might take a couple of runs but it really does help. I put in the intake and the tank but dont like the idea of the oil.
http://www.seafoamsales.com/motorTuneUpTechGas.htm