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Discussion Starter #1
I have a 2000 Chevy Z71 truck with a 5.3 engine and a 10,000 lb towing package. I tow an enclosed trailer and my boat alot with this truck. It tows great but on a long grade it runs at 4000 RPMs in secong gear while pulling the load at part throttle so it sees frequent higher RPMs at times. It has 82,000 miles on it now and I notice it has a knock when it's cold and first cranked up in the morning. It sounds like a piston slap sort of but it goes away before you go 1/8 mile and it is the same in the extreme cold as it is in warmer weather. Seems to me if it was a piston it would take longer to warm up and stop in the winter. Anyone smart about these new motors and have any experience with them. Do they have a problem with pistons? It runs great and has been well maintained and the oil pressure is still the same as it's always been at 50 lbs or so but this knock bothers me. RM
 

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I have a 2000 Sierra with the 4.8 L. I have noticed the knock that you are talking about as well.I asked the dealer about this and they infomed me it has to do with the way the bttom ends are built in these engines.I believe it is the way the blocks main caps are held in place and this transmitts this knocking sound.I have listened to several of these trucks running,with both the 4.8 and 5.3 and they all do it.I ahve had the truck for five years.Has done it since day one.The truck has app. 60,000 miles
I tow a 26 foot 4500 lb travel trailer.I find that in "tow haul" mode I have to let off a little on the gas to get the truck to shift gears or the tranny will hold at the higher rpm.
Hope this helps.
 

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There was a thread on this exact same subject a little while ago. I can't remember if it's in this forum or the BS section. What's frustrating is people don't post in the right sections or use descriptive thread titles and that makes searching harder.

I'm surprised the 5.3 is available with a 10,000 lb towing package. I would think you'd want the diesel or the 6.0L if you need to tow that much.
I worked in a Chevy dealer in '78 (second oil embargo days). People would buy the 350 instead of the 454 for their duallys because of the gas prices and then try towing big horse trailers. We installed a lot of replacement engines.
 

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Discussion Starter #5
Thanks for the reply. Mine didn't make this noise til last fall sometime. My old 4.3 in my 1989 S15 has had a piston slap for the past 50,000 miles but I know that and it acts just like any SB with how it slaps. Start it cold and it will slap for a few minutes and gradually fade away. The new truck makes this noise til you go to the next driveway and it's gone no matter how cold it is. You won't hear it again til the next morning either. Thanks again. RM
 

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Discussion Starter #6
While my slow fingers typed others posted.....LOL. I see there seems to be a problem now. Thanks for the replies. Paul, the truck has a 10,000 package in it. Took some work to find one but she'll pull that and a little more up through the mountains with very little effort really. Been to Ohio and back 3 times with the trailed loaded to the max plus and never run under 55 MPH. It will run 70/75 with the a/c on and gets 10 to 11 MPG doing it. My little S15 with a 4.3 is rated to pull 7,000 lbs. If it had 2 wheel drive instead of 4 wheel drive it would have been rated at 7,500 lbs. Pulled about 6,000 lbs most W/E for 100,000 miles and she's still doing fine today with over 150,000 on her. I love my Chevys.......LOL. Thanks again. RM
 

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Here's that thread 96 Vortec noise It's a 5.7 but it's similar to what you describe.
 

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My 2000 Suburban 5.3 has done it for a few years now--124,000 mi. still works just fine. I just drive slow for a few blocks and it's gone.
 

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I have a 1999 GMC Sierra with a 5.3. It has 82,000 miles and just started doing the piston slap thing this past winter. From what I've read it is common and not suppose be anything to worry about(according to GM) but it sure doesn't sound good.
BP
 

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Knock, knock..who's there?

My 2001 Tahoe has 155,000 miles and still keeps on knocking...excuse me, I mean slapping. I heard all the same stories from my GM dealer and I have just come to live with it. It raps hard when cold and worse in the cold weather.. I just let it warm up a little and it goes away. It is like having a truck with 2 motors...when it starts it's a diesel, that turns into a gas job!!

Someday it will just go bang and then I will deal with it.

wilma:shh:
 

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Here are some soc's from GM on the noise. Ed
Document ID# 1206539
2001 Chevrolet Chevy K Silverado - 4WD


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Subject: Engine Knock or Lifter Noise (Replace O-Ring) #02-06-01-038 - (12/02/2002)



Models: 2001-2002 Chevrolet Camaro

2001-2003 Chevrolet Corvette

2001-2002 Pontiac Firebird

2002-2003 Cadillac Escalade, Escalade EXT

2000-2003 Chevrolet Suburban, Tahoe

2001-2003 Chevrolet Silverado

2002-2003 Chevrolet Avalanche

2000-2003 GMC Yukon, Yukon XL

2001-2003 GMC Sierra

with 4.8L, 5.3L, 5.7L or 6.0L V8 Engine (VINs V, T, Z, G, S, N, U -- RPOs LR4, LM7, L59, LS1, LS6, LQ9, LQ4)




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Condition
Some customers may comment on an engine tick noise. The distinguishing characteristic of this condition is that it likely will have been present since new, and is typically noticed within the first 161-322 km (100-200 mi). The noise may often be diagnosed as a collapsed lifter. Additionally, the noise may be present at cold start and appear to diminish and then return as the engine warms to operating temperature. This noise is different from other noises that may begin to occur at 3219-4828 km (2000-3000 mi).

Cause
The O-ring seal between the oil pump screen and the oil pump may be cut, causing aeration of the oil.

Correction
Inspect the O-ring seal and replace as necessary. Use the applicable part number listed below. Refer to the Engine Mechanical sub-section of the appropriate Service Manual.

Parts Information
Part Number
Description
Qty

12557752
Seal-O/Pmp (O-ring)

(F and Y Cars)
1

12563963
Seal-O/Pmp (O-ring)

(C/K Trucks)
1


Parts are currently available from GMSPO.

Warranty Information
 

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Document ID# 1271016
2001 Chevrolet Chevy K Silverado - 4WD


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Subject: Info - Engine Knock on Cold Start #01-06-01-028A - (03/18/2003)



Models: 1999-2002 Chevrolet and GMC C/K Pickup and Utility Models

2002 Cadillac Escalade (2WD)

with 4.8L, 5.3L or 6.0L Engine (VINs V, T, Z, U -- RPOs LR4, LM7, L59, LQ4)




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This bulletin is being revised to add an additional engine to the models section. Please discard Corporate Bulletin Number 01-06-01-028 (Section 06-Engine).


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Some of the above vehicles may exhibit an engine knock noise that begins in the first 19,000-24,000 km (12,000-15,000 mi) of use. The knock noise is most often noticed during initial start-up and typically disappears within the first 5-30 seconds (may last longer in extreme cold temperatures). The noise is usually more noticeable on the initial start-up when the temperature is below 10°C (50°F) and may be more pronounced on the first cold start following a long trip.

This noise may be caused by an interaction between carbon that has formed on the piston, the piston motion and the cylinder wall. GM Powertrain Engineering, and an analysis of engines with this condition, has confirmed that the noise is not detrimental to the performance, reliability or durability of the engine. THIS NOISE DOES NOT HAVE ANY EFFECT ON THE LONGEVITY OF ANY OF THE ENGINE COMPONENTS.

Important: At this time, attempts to repair this condition by replacing the engine assembly or pistons are not recommended.

Please share the information found in this bulletin with customers who inquire about this condition. In the event they have additional questions or concerns, please advise your Area Service Manager.
 

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Document ID# 1769091
2001 Chevrolet Chevy K Silverado - 4WD


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Subject: Generation III V8 Engine Piston Repairs - keywords crank crankshaft cylinder engine knock L59 LM4 LM7 LQ4 LQ9 LR4 LS1 LS6 noise pin piston repair rod tick #PIP3691C - (02/23/2006)



Models: 2002 Cadillac Escalade

1999-2005 Chevrolet Express, Silverado

1999-2005 GMC Savana, Sierra




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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
A dealer may be in process of making a mechanical piston or crankshaft repair. There are engine mechanical differences that may be encountered depending on the year of the vehicle. When repairing a Generation III 4.8 5.3 or 6.0 V8 engine it may have a pressed fit piston pin. If GMSPO does not have stock on the pressed fit piston pin, a repair can be made with a new full floating style piston.

Recommendation/Instructions:
Below is a description of V8 engines and piston repairs.

4.8 5.3 and 5.7 engines with RPO codes LR4, LM7, L59, LS1 and LM4.

Full floating piston pins went into 4.8, 5.3, and 5.7 engines with the start of production in the 2005 model year.

If a dealer is servicing a 4.8, 5.3, or 5.7 engine that has a pressed fit style piston pin, a full floating style piston and rod can be used as a repair. If more than two pressed pin pistons need to be replaced with full floating pistons, it can cause a engine imbalance concern. If more than two pressed fit pistons need to be replaced with full floating pistons, replace all 8 pistons and install a 2005 model year crankshaft. If the engine has less than 100,000 miles the old piston rings should be reused on the new pistons. Install the rings in their original positions, and in the original cylinder they were removed from. No cylinder honing should be done when the old rings are returned to their original positions. Old pistons rings are reused so oil consumption will not be induced during the repair.

6.0 RPO Code LQ4

Full floating piston pins went into 6.0 LQ4 engines with the start of production in the 2005 model year.

2002 and prior model year LQ4 engines had pressed fit piston pins, and a first design crankshaft. If a piston repair is being made on a 2002 or prior model year LQ4 engine, and full floating pistons are being installed, the crankshaft must be replaced. The full floating pistons will not work with a 2002 or earlier LQ4 crankshaft. Use a 2005 LQ9 crankshaft and replace all 8 pistons when completing this repair.

All 2003 and 2004 model year LQ4 engines had the updated crankshaft but had pressed fit piston pins. The pressed fit pistons are the same weight and mass as a full floating piston. Mixing pressed pin pistons with full floating pistons will not cause a engine imbalance. If the engine has less than 100,000 miles the old piston rings should be reused on the new pistons. Install the rings in their original positions, and in the original cylinder they were removed from. No cylinder honing should be done when the old rings are returned to their original positions. Old pistons rings are reused so oil consumption will not be induced during the repair.

6.0 RPO Code LQ9

All 6.0L LQ9 engines (from the start of production) came equipped with full floating piston pins. All piston repairs on LQ9 engines should be made with existing GMSPO replacement parts.

Note: Due to engine build dates, it is possible to have a late build 2004 engine with full floating piston pins. If the engine has full floating pistons, repair with current GMSPO floating pistons.

Note: SI procedures for the Engine Block Inspection / Piston, Connecting Rod, and Bearings Cleaning and Inspection, should be completed during repairs.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
 

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Yup, take your pick on the reasons. Mine is a lifter in the 2001 5.3. Same place, left front, goes away fairly quick. Running great.

One dealer told me it was the carbon build up. Then I asked what additive GM recommended to clean it up. He said they didn't recommend one. That sounded funny to me. Anyway with the long drives I go on through New Mexico, carbon build up doesn't have much of a chance.

One nice thing about the noise. The original owner was so upset, the regional rep gave the engine a 100,000 mile warranty. I have it in writing! If it blows at 99,999.99 miles, I get a new engine from GM. Hopefully I wont need it.
 

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Engine noise..

I was also told about the carbon build up contributing to the noise. One Chevy dealer told me they can clean the carbon out of it and the noise will go away for awhile. We also talked about the 100K warranty issue, but since I now have 150k plus it doesn't matter. I may look into the carbon cleaning process and see what gives...


wilma:shh:
 

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Well my 2000 5.3 has had the "slap/knock" since I bought it with 42k on it. Now showing 160k, mostly highway miles @ 70+mph. Never any engine problems before. Running Mobil 1 since 60k and kept it changed on time. Last weekend something went wrong and I got a lot of valve noise. I pulled the valve covers and I have a lot of slack (about .125) between the rocker arm and valve tip on 3 valves. The rockers looked and felt ok, and the valves are all the same height, so I'm thinking bad lifters. The cam lobes I can see look ok. Boy was I surprised when I pulled the valley cover and couldn't get at the lifters! I've never worked on a gen III before, but I now know I have to pull the heads to replace lifters.
Anybody ever run into anything like this? Any clues on checking the lifters? Do I have to replace the headbolts? I was planning on spending this money and time on the nova project, not the pickup....so not a happy camper.:(

Thanks,
Jeff
 

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I've had a few customers not hear the noise until later in the vehicles life so it's not always there from day one I guess. Some make noise and some don't. I guess it depends on how loose the pistons are setup. Carbon could be something to look into. You might want to try using some GM top engine cleaner. Directions are on the back. I like to get the engine hot run A bottle through then use another bottle and put it in a little heavier and shut the engine off while it still going in and let it soak for 15 minutes or so before starting it back up. When you fire it back up take her for a blast to blow out any loosened up stuff before it gets real hard again. Then change the oil of course.

The piston slap is in almost all the LSX engines due to the short piston skirts but I've yet to see it cause a real problem other than noise. I bought a 2005 GTO and it had it almost until the car was warmed up between 2000 and 2500 RPMs mostly but it was there almost from day one. Most people would not have heard it but it was there.

I didn't like it at all, just try and not let it get to you.
 

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Discussion Starter #19
It is old. I traded that truck in last summer and it had 105,000 miles on it then......LOL. RM
 
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