TNRAT

I hear a clicking, almost knocking noise coming from the front of the engine. Only does this when the car is first started and the engine is cold.....once the engine warms up the noise goes away.....did a search but did not find any "clicking issues" that matched mine.....

ajg1915

Well I would begin by popping open the hood and starting the car up and trying to isolate the noise.

A general noise like you described could be anything. It could be a belt, pulley, loose rocker, etc ...

Whatever it is, it goes away when the engine warms up meaning that the clearance is tightening up and making the noise go away.

I would also check the DIC for codes.

TNRAT

No codes set.....Best I can tell by ear is the noise is coming from maybe one of the pulleys...the crank pulley looks like it has a slight wobble....dont know if that is normal for a bowtie?.....

ajg1915

Crank pulley is not suppose to wobble. It's a sign that the balancer is starting to seperate or the front bolt is coming loose

You have front tensioner on both the AC and serpentine belts.

I would pull off both belts and start the car. If you hear no noise then you isolated it to the front drive componets.

Start with the AC and if no noise, look at the belt and check the grooves to see that they are not damaged and then check the other pulleys for free play or wobble.

Re-install the belt and figure out which items is causing the problem.

jmckeer8199

piston slap till the alum block warms up to better fit the pistons????

helga203

possible water pump????

ricknyc23

I vote for piston slap. I have that too. Nothing to worry about...

TN Vette

My 99 doesn't do it, but only has 43,000 miles.
My 2000 Silverado 5.3 started this at around 50,000 miles and does it mostly in cold weather on the 1st start of the day. It makes the noise for about 2 minutes at idle, then it disappears. The truck now has 124,xxx miles and doesn't burn oil. =)

Paul 75 L82

It's a common problem with Lexus.

TNRAT

My car has 41,000 on it....so if it is piston slap it wont affect modding or a hard evening at the track?......would a different weight oil stop the slap?..

kp1

In my experience piston slap cannot be diminished by using different oil or different weight oil.

TN Vette

If it is piston slap, the only way to get rid of it is replace the pistons with a different set that has the correct size or coating on them.
But to be honest, it isn't worth the money.

My truck has had piston slap for over 5 years and I have tried additives, 0-30w Mobil 1 and really no change.

The only thing I have noticed is that right after an oil change with fresh Mobil 1, it doesn't seem to do it the first couple of cold starts for some reason.

If you aren't burning oil and it is piston slap, I would not worry about it.

It only happens when it is cold and as long as you don't drive the car hard when it is cold, you should be fine. Always run the 5-30w synthetic in the car too, changing weights could cause engine damage, especially in cold weather.

dgrant3830

The ticking isn't coming from the valve cover areas? If it is, then its more likely lifters bleeding down when cold but unless you have a ton of miles, its rather unlikely.

Z06X

Piston slap...wtf. Forged pistons yes, hyperuetectic pistons...no. A forged piston requires more piston to wall clearance due to the nature of expansion in that material to obtain proper piston to wall clearances at operating temp. Hypereutectic pistons have a high silicone content and don't expand in the same manner, but also can't sustain high heat like a forged piston can, plus forged is stronger...hence why big power motors go forged. Aluminum "block" has nothing to do with piston to wall clearances becuase your bores aren't aluminum.

If you have piston slap in a stock motor you got problems due to wear. A motor can have piston slap and run somewhat fine, but I highly doubt a lower mileage LSx motor is gonna have blown out piston-wall clearances or bellmouthed cylinders. Piston slap is a misdiagnosis. I'd look more to a lifter needing replaced or something in the pulleys. Lifters will tick until they "pump up" upon startup sometimes or they'll just tick endlessly...and sometimes heavier weight oil quiets them down. Heavier weight oil than needed costs you horsepower though...it's a fact.

Pewter Scooter

I never hear it coming from my C5, but I've got a 1997 Z-28 with an LT1 that has done it since it was new. I always thought it was rattling lifters. As soon at the temp guage starts rising, the clattering stops.

200,000 miles on it now, with no problems. I just never romp on it until it's nice and warm.

TN Vette

The following is a quote from this link: http://en.wikipedia.org/wiki/GM_LS_engine

"Problems:

In the early production run of the LS-series engine, some engines encountered abnormal amounts of 'piston slap' - a problem caused by too much clearance between the cylinder bore and the piston.[11] 'Piston slap' sometimes sounds more like a knock or the sound of a diesel engine running. It is typically worse when the engine is cold and lessens as the engine reaches operating temperature. The noise of 'piston slap' often is louder when listening for it below the oil pan.

"

I have a 2000 Silverado with a 5.3L engine that I bought new that now has 124,xxx miiles and it started the piston slap at ~50,xxx miles. It never burns/uses oil in its 5000 mile oil changes with Mobil 1 but in cold weather sounds like a diesel engine for about 2 minutes while idling.

Though it may not be the OP's actual issue, it sounds a lot like it.










For anyone wanting more information on GM's Piston Slap:

http://www.pistonslap.com/index.html

tlc0706

I also have an older Z-71 (5.3) w/186,XXX miles that makes the diesel noises on cold start-up. Changed oil about a month ago to Mob 1 10W30....haven't heard the noise since........Will it return? Probably! But, for now I can start without scaring little children and women.....

TN Vette

I've noticed that since I started using Mobil 1 5w-30 and 0w-30 that for the first few times I drive it after changing the oil that it stops the noise for a little while. Then, it starts the noise again a few cold starts later.

TNRAT

The oil change deal may be the reason I didnt hear this when I was trying out the car....the dealer had just changed the oil.. I have put about 800 miles on the car since I started driving it and the dip stick still shows right on the full mark.......makes you wonder what is going on with the oil itself that it would stop slapping when fresh and not after only a short time...

joe Villarreal

its piston slap engine oil us at the bottom of oil pan at start up till oil flows through engine this noise is normal you might want to add lucas synthetic oil staibilizer to quiet this a little.