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Engine Knock

seadoons

Do you have it and when?  

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Gregg1LE Enthusiast

Gregg1LE

Posted
Posted

I had ticking sounds at startup with my 2000 Z28 5.7L LS1, but nothing with my '07 Silverado with the 4.8L. I'm hoping things have improved :withstupid: since then.

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mlkyllo New Member

mlkyllo

Posted
Posted

My '03 Z71 Silerado has what sounds like a timing knock at startup (timing to far advanced)...it only has 39000 miles on it.

The gas mileage also sucks running between 13-14 mpg on the highway empty, but gets 12 mpg towing a loaded car trailer.

The tailpipe is also black with soot, so it is pumping the fuel into it, but supposedly it is running fine after being checked...guess I don't buy it. :)

rwick3142 Enthusiast

rwick3142

Posted
Posted

My 2001 Yukon XL knocked like crazy at cold start up. I added sealant to the radiator and it took care of the problem. Before that I had 3 different GM dealers tell me I had to replace the motor, she ran for another 50,000 before I (my wife) trader her in. Their is a webpage called Piston slap.com that goes further into "pistonslap"

  • 2 weeks later...
Westlotorn Enthusiast

Westlotorn

Posted
Posted

To clarify the question about engine knock please note what engine you have.

 

The 5.7L 350 Chevrolets are known to knock on start up. # 1 Main Bearing is getting loose.

You hear a deep knock that hits only a few times and quickly gets softer then leaves as oil is pumped into the main bearing.

Usually above 80,000 miles. No need to panic unless it gets worse. Will run many thousands of miles after first hearing it.

Will be louder the longer the vehicle is parked and maybe not there at all on a short term restart. If it does not get worse I would not worry about fixing it till you have a reason to open up the engine for something else. I put new main bearings in my 1995 Suburban to eliminate this noise at 155,000 miles. Lot of work and you risk causing other issues when you open an old engine and don't do a complete overhaul.

A friend bought this from me and it is still quiet and strong at 190,000.

 

The newer family, 4.8L, 5.3L and 6.0L suffer piston slap on start up. Not all but some do it.

Should only hear this on cold start. The block must be cold. Pistons will rattle till temperature on the piston makes it grow a little and then they are quiet. This one can start when the truck is brand new and do it till you retire the rig.

This noise should go away in 10-15 seconds. If it is longer or does it in all conditions it may be another issue.

Piston slap is worse in cold weather and better in warm weather. It won't shorten the life of your engine.

GM is running short skirt pistons in these engines, just like racers have always done. ( last 20 years anyhow ).

It is hard to run a quiet short skirt piston in a working engine but GM has done it quite well.

They help with Power and Mileage, negative is noise on start up.

Some of you may remember this noise from building high power engines with Forged Pistons in the 60s through the 90's.

The Forged pistons used to need more clearance and made noise on start up.

Have not seen any bearing failures on this family of engines unless they are not maintained.

My 2001 Denali 6.0L had the noise from new till sold with 89,000 miles, I hated the noise. My 2002 Tahoe 5.3L does not have it yet at 80,000 miles, luck of the draw.

  • 3 weeks later...
Robbg12 New Member

Robbg12

Posted
Posted

I have a 2003 Chevy Silverado 1500 with a 5.3L. I bought the truck used about a year ago and now the truck has 46,000 miles on it. A few weeks ago i noticed a tick coming from the engine, you can here the tick in the truck and u can really hear the tick when you are under the truck. The tick is not as loud when i first start it up in the morning, but after the engine warms up the tick becomes louder. I have also found that while i am driving on the freeway the tick gets very loud when i take my foot off the gas and coast, and i can not really hear it as loud while i am accelerating. I use Valvoline 5w30, and am not really a hard driver. Ive tried different cleaners and stuff and nothing is working. Do u have any idea what it could be or anything that i could try to get rid of the tick?

redvett Senior Enthusiast

redvett

Posted
Posted

No knock at 2000, 01,03 & 04 mileage ranges between 240000 on the 2000 to 35000 on my 04 all are 1.2 T EXT 4x4 used in my electrical business.

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unit731 Senior Enthusiast

unit731

Posted
Posted

1990 Chevrolet 1500 regular cab long bed 4.3 manual transmission Scottsdale. 136,000 miles.

 

Truck has had knock at start up since day one.

blueflavor Enthusiast

blueflavor

Posted
Posted

Yep i have a 2000 z71 and it clickity clacks on every cold startup. Was told its piston slap and stops when motor gets warm due to the expand and contrast stuff

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