Engine Tapping as if NO OIL

I have a 1999 Silverado with a 5.3l V8 that I have babied since I owned it. I bought it used (1 year) and noticed early on that there was a VERY BRIEF tapping on engine start-up which disappeared after only a second or two. This was more prevalent in the cold New England winter months.

Lately however the problem has become much scarier as the tap-tap-tap noise (indicative of low or no oil pressure) persists while driving out of my driveway and as much as 100-200 feet up the street at normal acceleration. It's getting LOUDER too. I always use 5W-30 year round and use quality oil. The oil levels are fine, always clean, no leaks. For the sake of disclosing everything, I feel I do have an oil sender problem. Sometimes I look down and see the guage pegged max high. If I drop it in neutral it returns to the middle of the guage about 40 psi. (By the way, does anyone know WHERE the sender is on that engine? I can't find it for the life of me) . Engine has 49,000 miles.

Thanks, Paul

Sounds like "piston slap".. My 02 6.0 just started doing it and it has 18k on the clock. To me its a valve train problem with oil pressure, cause I can park it certain ways and it won't do it as bad. There is a service paper out for a split "o" ring on the oil pump pick-up. The dealer has to test the truck to see if this is the problem.. How do they do this?.. but When I called the service guy started laughung when a was telling him my problem and said "yup its most likely piston slap and it normal for these motors to do it and GM is doing nothing about it... Great my first new truck in 17 years and I bought a slapper.. I'm not very happy

I have 2000 Chevy 6.0 and it has occasional piston slap. I will have the compression checked just before the warranty go's off

That cold engine tap is not a Chevy exclusive problem. To solve the problem for little or no cost clean the mass air flow sensor with electrical contact cleaner. It is located in the clean air duct between the air filter and the throttle body. Don't touch or wipe the metal wires(bars), just spray liberally, let dry and replace. It should solve your problem and save you big bucks

It Is A Chevy Problem. I Have A 2000 Z71, And In The 325/5.3 Motors Chevy Had A Bright Idea To Have Less Rotating Mass And Make The Piston Skirt Shorter And Keep The Same Diameter Piston Which Causes Piston Slap. And Also The Extra Carbon On Top Of The Piston Doesn't Help Much Either

My 2000 Z71 did the same thing. A Ford owner that had the same problem found the solution I suggested on a web site called fordsucks.com. It worked for his Ford and my Silverado.

gordonfan has a good idea to try- it's cheap and can't hurt.

What happens if you were to run straight 30w in the crankcase. Though not advisable in your area (or mine in Indiana) throughout the winter, it's ok to run in warmer weather. You might even try 10-30 with your next change just for kicks.

Several European cars I've worked on have also done this on warmup. Not enough oil where it needs to be on the top side, then after things pump for a second things are fine. Most of these cars require 15-40 oil. If that's not used in them, they will rattle a little more until warm.

Your gauge dancing around sounds odd so you'd be wise to look at that as well. That could mean the pump is bad, the gauge is bad or if you have luck like mine- both are bad.

I'm not sure about the "piston slap" thing. With the reccomended oil and a motor that has low miles, it seems unlikely it could happen unless the truck has seen lots of abuse. But I could be wrong?

You mentioned it getting louder and for a longer durration- that would get me into a good mechanic ASAP if the fixes posted on here don't help.

I have a 2001 Chevy Silverado and was told that this was called Cold Engine Knocks. Chevy said it was from carbon build up on the pistons. They cleaned it with Top Engine Cleaner. The knocks came back in less then 3000 miles. My Brother ( a mechanic) told me to NEVER let Chevy use that again on my truck because it will short the life of my vehicle.. You would think that Chevy would know this.

Just curious...is it a single or multiple knock? Sounds like a lifter going bad, especially if it's getting louder, longer.