Infamous Piston Slap Question is my problem really Piston Slap?

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by bobbyg35, Aug 8, 2011.

  1. bobbyg35

    bobbyg35 New Member

    My truck is a 2002 Chevy Silverado LS 1500 4x4, and around 60,000 miles or so I started to hear a knocking/slapping sound coming from the engine during idle. I know about Chevy piston slap because my 2001 Silverado had the bad knocking sound when I started my truck.

    This time it sounds different, not so much as a loud knock or slap, more like the lifter is not working properly. Has anyone ran into this problem on their truck? If so did you get any results from the GM dealership or from your own repairs?
  2. davedyno

    davedyno Member

    You will find endless info and sound clips on the net about this problem. I feel GM is right about the motor won't blow up, it's just sounds that like a rod knocking or severe lifter noise. On a real cold morning it sounds like the rod is ready to let go. It's hard to say what a GM dealer would say now, they might now hear the noise if your paying for the repairs. In the winter on those very cold mornings I would start the truck up to warm up and several of my neighbors would just stop and stare. On the plus side the 4.8 was a hard working motor for 9 years and never let me down, never used more then a half a quart of oil between changes.
    2011 Silverado Ext 4X4 5.3 Z71
    Leer Hard Body Tonneau lid
  3. billnorman

    billnorman Rockstar 100 Posts

    A chronic issue especially with the earlier smallblocks. If, just if the problem is caused by dirt or sludge I have found what worked for me on my spouse's (Dodge) passenger car. It sounded like an anvil chorus when cold. I waited till I was about to change oil, and added a can of Seafoam to the hot engine. I let it idle for about 15 minutes, then changed the oil and filter. It did quiet down before I drained the oil, and has never made any more obnoxious noises in the 20,000 miles since. Try it at your own risk, but it worked for me.
  4. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    We found that when we used Wix or NAPA Gold (Wix) oil filters we didn't get any engine knock, slap etc.. , don't know why this worked. We wondered if they flow more oil at start-up? When we tried a NAPA Silver (cheaper brand) filter we got the knotck and slap.

    ---------- Post added at 12:13 PM ---------- Previous post was at 12:07 PM ----------

    I've owned my truck since new and after breaking the engine-in, I have run Wix filters and Mobil 1 synthtetic oils. It is now pushing 89,000 miles and has never had any piston slapping or knocks.
  5. davedyno

    davedyno Member

    I agree NAPA GOLD AND WIX (Same Filter ) are the best and Mobil 1 synthetic oil did help with the noise. But you know in the long run I made out OK again. Nine years is a long time for a car or truck and these dealer's have a lot a young people working for them now in sales and the shop, it's very hard to hear the noise with a warm motor on a hot day. Why I say "again" the first time I had major problem with GM was 1971 with a Chevy VEGA after having the car for about a year it was using 2 quarts of oil a week and I was told then I could go to a another dealer. Well I did and traded it in on a dark raining cold night in January 1972. So when you are told you can go to another dealer think positive it just may work out. That was 40 years ago.

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