I have an occasional knock in my engine.
If I drive my 01 coupe, say, 8 hours or more of steady driving in a single
day, then park the car for the night. The next morning when I start the car
the engine has a loud knock for 3 to 4 minutes.
If you have heard an engine with a rod knocking it is almost this bad.
Has anyone heard of this before? :eek:

 

I am no Expert, but i believe this is "Normal" for all LS1 Platform engines.

I had a 99 5.3l in my truck and it did it at every cold startup. I complained enough to GM and they gave me a 100k warranty on my engine. I recently sold the truck with 80k (to get my c5) and the engine was still running like new.

I noticed on my 00 that it does the same thing - so i am not concerned. (that and i have a 70k warranty on it)

 

Sounds like "piston slap"... GM says it is normal and is caused by the "barrel shape" of our LS1 pistons. I say GM quality stinks. :mad Anyway, I was told to drive it easy until it is up to temperature and the engine will hold up just fine.





[Modified by chuck1026, 1:03 PM 3/30/2003]

 

:iagree: That is excatly what it is.

 

I had a '92 vette who's engine, when cold, made the strangest noise between 2500 and 3000 rpms. You couldn't hear individual "knocks"; it was more like a "rough" sound. Anyhow, I thought it wasn't right. Then, I test drove a few more LT1's, and then my dad's LT4, and they were all the same. I figured it was normal.

Then I got a C5 with the clean-sheet redesigned LS1 engine, and guess what? Same exact noise.

 

Wow, I’m so glad you brought this up as I have been hearing the same thing when I go up my steep driveway after a cold start.
I wasn’t too worried about it as I have an 85,000 mile warranty on it, but I was curious about what was going on.

Thanks,
Gordon. :steering:

 

Sounds like piston slap. See your dealer.

 

I agree on both, slap and see dealer. The following is a GM bulletin related to "engine noise" Had pistons and rings done in son's 00 coupe with 13k on it.
"
Document ID # 215373
2000 Chevrolet/Geo Corvette

Engine Noise Diagnosis
Symptom Cause
There are four steps to diagnosing engine noise. You must determine the following:
 The type of noise For example, is the noise a light rattle/tapping or a low rumble/knocking?
 The exact operating condition under which the noise exists Note factors such as the ambient temperature, the amount of engine warm-up time, the engine temperature, engine RPMs, and other specifics.
 At what rate the noise occurs, and at what location in the engine Remember, engine noises are generally synchronized to either engine speed (crankshaft, flywheel, connecting rods, balancer, or pistons and related components) or one-half engine speed (valve train noise such as rocker arms, valve lifters, and timing chain). Try to determine the rate at which the noise is occurring.
 Compare the engine sounds to other engines and make sure you are not trying to correct a normal condition.
Noise on Start-Up but Only Lasts a Few Seconds  Improper oil viscosity. Install the recommended oil viscosity for the expected temperatures.
 Incorrect oil filter without the anti-drainback feature
 Worn or dirty valve lifters
 Excessive piston to bore clearance
 Excessive piston pin to piston clearance
 Excessive crankshaft bearing clearance
Knocks Cold and Continues for 1 to 2 Minutes  Loose or broken crankshaft balancer or accessory drive components
 Excessive piston to bore clearance A cold piston knock which disappears in 1.5 minutes should be considered acceptable.
 A cold engine knock usually disappears when the specific cylinders secondary ignition circuit is grounded out.
Intermittent Noise on Idle, Disappearing When Engine Speed is Increased  Improper oil viscosity. Install the recommended oil viscosity for the expected temperatures.
 Lower than specified oil pressure Install an oil pressure gauge and measure the engine oil pressure.
 Dirty or worn valve lifter
Valve Train Noise (Rattle/Tapping) The following conditions may cause valve train noise:
 Lower than specified oil pressure
 Worn or faulty oil pump
 Loose oil pump-to-engine block bolts
 Loose valve rocker arm attachments
 Worn valve rocker arm bearings
 Worn valve rocker arm and/or pushrod
 Broken valve spring
 Sticking valves
 Worn, dirty, or faulty valve lifters
 Worn camshaft lifter lobes
 Worn valve guides or valve stems
 Bent, broken, or damaged timing chain sprocket teeth
Knocks at Idle Hot (Rumble/Knocking) The following conditions may cause a knocking noise:
 Malfunctioning accessory drive system components
 Loose or broken crankshaft balancer
 Loose prop shaft hub or clamp (Corvette only)
 Detonation or spark knock Check for proper operation of the cooling, knock, and ignition control components. Refer to diagnostic information in Engine Controls.
 Excessive connecting rod bearing clearance
 Excessive piston pin to bore clearance
 Bent connecting rod
 Excessive crankshaft main or thrust bearing clearance
 Loose torque converter bolts
 Cracked or damaged flywheel
 Exhaust leak at the manifold
Exhaust System Noise and/or Leakage Exhaust system noise and/or leakage may be caused by the following conditions:
 Improperly installed or misaligned exhaust system components
 A cracked or broken exhaust manifold
 Damaged or worn gaskets and/or seals
 Burned or rusted out exhaust system components
 A broken or loose exhaust clamp and/or bracket


I have it as a Word document, I will email to you.




[Modified by Stilcrazee, 10:06 PM 3/30/2003]

 

Thanks for the information guys.
I took the car to the dealer today.