Slight knock?

[tybcr783]

Hey y’all, 2000 Chevy c2500 5.7/4L80-E
166,000 miles. Slight knocking noise on startup, disappears after little bit, see attached vid.

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[scott2093]

Kinda short video...
Is yours the year where people talk about the oil pickup o-ring/seal that can cause issues?
Maybe someone can chime in that knows.....

 

[Schurkey]

No O-rings on the suction side of the oil system of a 5.7L. The O-rings are on the LS-series engines.

Knocking on startup of a 5.7 is often
1. Faulty oil filter anti-drainback valve. Need an oil filter that has an anti-drainback valve, or one that has a WORKING anti-drainback valve. Some filters "have" an anti-drainback valve, but they're poorly made from inferior materials, and they don't actually seal.
2. Hydraulic lifters that bleed-down excessively.
3. Piston slap. GM says it's harmless. In mild cases, they're right.

 

[someotherguy]

If it does it only on cold starts, doesn't do it on warm re-starts.. let's not forget the possibility of the good ol' cracked flexplate.

Richard

 

[scott2093]

If it does it only on cold starts, doesn't do it on warm re-starts.. let's not forget the possibility of the good ol' cracked flexplate.

Richard

Are you saying that lifter bleed down or anti-drainback valve not working are only applicable to cold startup?
What would cause random tapping at startup, even warm, that goes away?

 

[0xDEADBEEF]

If I had to guess, I would guess #3 in Schurkey's list. The 260k 5.7 in my Tahoe does it to and it won't die!

 

[someotherguy]

Are you saying that lifter bleed down or anti-drainback valve not working are only applicable to cold startup?
What would cause random tapping at startup, even warm, that goes away?

Well, I wasn't addressing those situations - what I'm offering is another possible source for the knock. It's not exactly common, but not rare, either. If the symptoms match what I described it's worth looking into.

Richard

 

[Scooterwrench]

Sounded like an old,loose motor to me. ADV's will help get the oil up quicker but it's still an old motor with lots of run time. Go to a heavier oil. You're down here in my neck-o-the woods and it's about to start getting hot so I would recommend 20w-50 high zinc. How's your oil pressure?

 

[tybcr783]

Sounded like an old,loose motor to me. ADV's will help get the oil up quicker but it's still an old motor with lots of run time. Go to a heavier oil. You're down here in my neck-o-the woods and it's about to start getting hot so I would recommend 20w-50 high zinc. How's your oil pressure?

My oil pressure on startup is great, usually like 60, but it fluctuates driving I’m probably at 38-41, whenever I’m stopped or idling it’s 20. I’m running factory setup 5w-30 Mobil one high mileage with a mobile one filter

 

[tybcr783]

No O-rings on the suction side of the oil system of a 5.7L. The O-rings are on the LS-series engines.

Knocking on startup of a 5.7 is often
1. Faulty oil filter anti-drainback valve. Need an oil filter that has an anti-drainback valve, or one that has a WORKING anti-drainback valve. Some filters "have" an anti-drainback valve, but they're poorly made from inferior materials, and they don't actually seal.
2. Hydraulic lifters that bleed-down excessively.
3. Piston slap. GM says it's harmless. In mild cases, they're right.

1. I run a mobile 1 filter, do you know how decent those are ?
2. I’m not sure what you mean by bleed excessively
3. Saw that a couple times on the forum and it’s probably this case, there’s hasn’t been a negative effect on mpg or the oil loss. She does leak or burn a small bit of oil, usually have to put half a quart before every oil change at 5,000 miles