Engine Knock

Sniper · November 30, 2007

2000 sierra 5.3 with 140,000 knocks on startup when the engine is cold.after warms up no knocky.

Wow! You actually counted the knocks? Just kidding. I read that and couldn't resist...

mizzoueng · January 21, 2008

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.

Its been really cold here lately, i noticed a knock at startup but it went away. This is the answer I was looking for.

2000DV4.8 · January 27, 2008

I've got piston slap on cold starts in my 2000 4.8L. 166,000 miles, and still running strong, so I guess it's not too big of a deal.

GasHog369 · February 3, 2008

mine knocked a little on startup , but ever since i switched to royal purple it has disappeared.

04z71steve · February 3, 2008

mine knocked a little on startup , but ever since i switched to royal purple it has disappeared.

i'm switching to royal purple soon! i'll let u know if i see the same change!

99xjsport06 · February 3, 2008

2004 Silverado 4x4

5.3L V8

Used to knock last winter every cold start up...no matter if it sat over night, or sat for 4 hours. Knocking lasted approx. 5-15 minutes depending on how long it had sat. Oil consumption at the time was approx 1-1.5 quarts per 3K.

As of this winter, no more knocking. Oil consumption has increased however to 3-3.5 quarts per 3k.

Mileage on engine at the moment is 112K, all highway.

Still blows out a fair amount of oil on a cold start up if parked facing up hill.

troopythetrooper · February 5, 2008

I just purchased a 2002 Chevrolet Suburban 8.1 66k miles. What ever oil was in it originally it made NO noises at all. I then switched to Rotella 5w40 synthetic and it had bad Piston Slap and a little Rod knock when 25 degrees or below.

Switched to dino 5w30 and AC delco filter no rod knock but still does the piston slap thing when it sits for a few hours/not as bad. It also does it very lightly as it comes down from idle.

I wish I knew what exactely what was in it. Besides all this its seems to be a great truck, I think I still liked my 93 with the Tonawanda 454 better. Oh well.

hookd · February 17, 2008

1999 5.3 137,000 miles knockes on cold starts after that its good to go.

strafingmoose · February 19, 2008

2003 C1500 4.8, 60k miles, no knocks at all.

punmax · February 20, 2008

Can somebody explain to me what you feel when you get knock/pinging? My engine when at idle will vibrate a lot... I will mention in it next oil change.

d3athsong · February 20, 2008

Can somebody explain to me what you feel when you get knock/pinging? My engine when at idle will vibrate a lot... I will mention in it next oil change.

Youll hear it if its knocking or pinging

dk1125 · April 2, 2008

I had a 2000 sierra with 6.0 and 162,000 miles Sounded like a diesael on start up, mostly when it was cold outside. But it ran great only repair done to the engine was I relaced knock sensors 1&2 as per the emc code i was getting. I traded it off in dec.07 for an 08 sierra, the only reason for getting rid of it was I needed the ext. cab for the family. BEST VEHICLE I EVER HAD!!! P.S. I realy miss that truck