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LOUD cold start knock ... goes away in 20-30 seconds after startup

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by SurrealOne, May 9, 2013.

  1. Sir Koscoe

    Sir Koscoe New Member

    I too have this noise on my high mileage 4.8. Thanks for all of the great comments. I am skeptical about using additives, but I have heard good things about Seafoam. This may be in the works soon for me.
  2. RAV52202

    RAV52202 New Member

    I have a 2002 2500 with 166,000 miles on it. I added a can of sea foam to the fuel tank. I could notice the closer I got home the better the truck was running. about a 25 mile ride. I would recommend sea foam to people. At least as a fuel additive. I haven't decided if I would add it to my oil before I change it.
  3. koolbia

    koolbia New Member

    Yes, welcome to the club! My 155K mile 5.3L 2001 Tahoe has what I lovingly refer to as a "lifter knock." No harm just annoying. Dealer told me to run heavier weight oil but it made zero difference. No repair needed, know you aren't alone.
  4. PantheraUncia

    PantheraUncia Active Member 1000 Posts

    I go between Sea Foam and Techron, I actually like the Techron better and buy it when they have it buy one get one free.

    http://en.wikipedia.org/wiki/Techron
  5. stchman

    stchman New Member 1000 Posts

    When I had my 1998 Chevrolet W/T with the 4.3L engine, I would get a little knocking noise upon start up. This occurred when it was new.

    After talking with a few mechanics, it was not the oil pump as the oil pressure was fine. It turned out to be the oil filter. I was using an aftermarket oil filter, I think it was Deutsch or some kind of Champ filter.

    To make a long story short, I switched to an AC Delco oil filter and the ticking went away.

    Ever since then, I ONLY use OEM oil filters. Even when I had as Explorer, I used a Motorcraft oil filter. Seeing as the AC Delco oil filters are no more expensive than aftermarket oil filters, why not stick with OEM?

    For your truck the filter is an AC Delco PF-46, make sure and avoid the E-core PF-46E.

    I would also recommend using Mobil 1 5W-30.

    As far as knocking is "normal" for Vortec 5.3L engines, that's a load of manure.

    Dumping some snake oil into the gas tank is not going to cure any problem except maybe cleaning the fuel injectors.

    A buddy of mine has a 2004 similar to your truck with ~185K on it and he said he's never had an issue with the engine knocking, and trust me he's not easy on his truck by any stretch.
  6. SurrealOne

    SurrealOne Former Member ROTM Winner 1000 Posts

    Thanks, that's good info!
  7. j cat

    j cat Active Member 1000 Posts

    the engine knock when cold and under load the first few minutes of starting the vehicle , is for some normal. this is because GM screwed up on the piston size/bore size. some engines needed to be worked because it would not go away even when warm. the under sized pistons would heat up expand and the knock would stop on most ,,,, but not all. the dealership then told many THIS IS NORMAL !

    IF on starting the engine and at idle in park the engine knocks ,,, then that is not a good sign ...

    adding techron or marvel mystery oil to the fuel cleans the injectors and reduces carbon in the combustion chamber especially if the injectors are not working correctly . this is used to reduce the knock that GM says increases this noise problem.
  8. stchman

    stchman New Member 1000 Posts

    Thing is [MENTION=50075]SurrealOne[/MENTION] has a truck with over 100K miles, and this is just now showing up?
  9. RAV52202

    RAV52202 New Member

    So Were can I find this Techron?
  10. JimmyA

    JimmyA Member

    My 2010 started to have a Lifter knock! Under warranty and the Dealer replaced all lifters. No more dry starts for me! According to shop manager (a friend of mine), this is common with the 5.3's. If you are having a deeper knock, a rod bearing replacement may be required! No rebuild, easy to do. I do them @ work quiet often on Cat Diesel engines.

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