Rattle On Start Up

grose67 · June 25, 2009

I have a 98 GMC Sierra with 5.7 engine. The truck has 14100 miles on it. I notice when I start the truck, it sounds like every bolt in the engine is rattling for about 1 or 2 seconds. Thr truck holds good oil pressure with 40 lbs idle and 60lbs driving. The engine is strong and runs great. Any thoughts?

superjim · June 27, 2009

You said that it has 14100 (fourteen thousand) miles.

Did you mean 141000 miles? (one hundred forty one thousand)

Either way...is the rattling noise happening after the truck is actually running, or is it happening during the actual starting process...ie...while you are still holding the key in the START position?

Is the rattling noise on EVERY START...or does it happen only after the truck has set for a few hours?

alwcurlz · June 27, 2009

I have a 98 GMC Sierra with 5.7 engine. The truck has 14100 miles on it. I notice when I start the truck, it sounds like every bolt in the engine is rattling for about 1 or 2 seconds. Thr truck holds good oil pressure with 40 lbs idle and 60lbs driving. The engine is strong and runs great. Any thoughts?

I'm guessing 141,000 miles right?

If this sound goes away after a short time, maybe 20-30 seconds and runs quiet, it's likely the infamous "piston slap" which is common on thousands of 4.8, 5.3, and 6.0 Vortec engines. Not sure about the 5.7 but, that's one thought about it.

Some other thoughts I have about your engine. What grade of oil are you using? Too heavy or too thin weight can cause irregular valve pressure. Possibly a weak knock sensors? How long have you owned this truck? When did this engine rattling sound start?

grose67 · June 27, 2009

I have a 98 GMC Sierra with 5.7 engine. The truck has 14100 miles on it. I notice when I start the truck, it sounds like every bolt in the engine is rattling for about 1 or 2 seconds. Thr truck holds good oil pressure with 40 lbs idle and 60lbs driving. The engine is strong and runs great. Any thoughts?

I'm guessing 141,000 miles right?

If this sound goes away after a short time, maybe 20-30 seconds and runs quiet, it's likely the infamous "piston slap" which is common on thousands of 4.8, 5.3, and 6.0 Vortec engines. Not sure about the 5.7 but, that's one thought about it.

Some other thoughts I have about your engine. What grade of oil are you using? Too heavy or too thin weight can cause irregular valve pressure. Possibly a weak knock sensors? How long have you owned this truck? When did this engine rattling sound start?

141000 miles. Rattle goes away after motor has run 2-5 seconds. Doesnt always do it, only after sitting all night or a few hours. Running 5W30 oil. I have only had the truck a few months . It has done since I have owned it.

pistonslap · October 4, 2009

Only 2-5 seconds? Does it do it when the motor is warm?? I have piston slap in my 2000 chev 5.3 silverado.When the motor is cold or has sit over night,the noises go like this.About 3 seconds of no noise at start up.Then the knocking starts and get louder gradually.Then depending how could it is it usually quits after about 30 seconds.