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OBD 4.8 Chevy lifter knock question. (edit)

Desert Whaler

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My Pops has a 2002 Short Bed Reg Cab Chevy with a 4.8, it just turned 100K miles, & he loves the truck.
Since day 1 it's had the famous valve-train 'tick' that goes away in about 30 seconds after a cold start.
That 'tick' has since turned into a 'knock' . . . it's only done it twice, last time was at the boat ramp friday and took a few 'minutes' to go away this time.
The drive home was 100% fine, no ticking or knocking.
He's made an appointment to take it in to his mechanic and I know it's not gonna be cheap. i'm guessing they're gonna discover a bad lifter.
Anyone have any experience with something similar ? Pops isn't made out of cash, so I just wanted to make sure I explored it a little before he takes it in.
His mechanic is good and thorough, and does things the right way . . . that's why he's not cheap.
Thanks in advance.
( Edit- he thought it was 5.3 motor but I looked it up and it's a 4.8 )
 
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jones performance

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its probalby a turned lifter and a flat cam, common issue in the ls paltform as the plastic lifter trays wear out.
 

Desert Whaler

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Buy a take out and swap it.

What's the oil pressure on startup? Could be caused by a bad Oring on the pickup. Known problem with a truck that age.
Just below 40 PSI at start up, and rises consistently with more throttle.
I haven't noticed any drop in PSI since he's owned it. He's really good about oil changes and tune-ups.
 

Flying_Lavey

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Also, these lifters are notorious for getting dirt/debris build-up in them. It could be that with a reduction in oil pressure while on an incline resulting in the knock? Or, like LOF mentioned, the oil pick-up O-ring. The incline was such that it caused the pump to starve more so than normal causing the knock.
 

Flying_Lavey

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$4k will buy you an entire, nicely-built crate engine from Brian Tooley Racing with a Stage 1 or Stage 2 camshaft…


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Unfortunately the OP's dad's truck is a 2002 so this engine would require a LOT of modification to work. However, Jeg's has LM7 short blocks ('99 to '07 5.3l) that are cranked up to 460hp for $3,700
 

ltbaney1

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i had the same thing in my '06 with a 5.3. i was all set to swap the lifters, until i figured out you have to pull the heads to do the job. drove it another year with no issue other than the nock and then traded it in when the tranny said no more.
 

Desert Whaler

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i had the same thing in my '06 with a 5.3. i was all set to swap the lifters, until i figured out you have to pull the heads to do the job. drove it another year with no issue other than the nock and then traded it in when the tranny said no more.
Thanks . . . I'm hoping it's not that . . . . I know it's a common deal on these motors. Since it has such low mileage for the age of the truck, I'm keeping my fingers crossed for a cheaper fix like LOF mentioned with the oil pick-up o-ring. I'm tempted to do a full sea foam engine flush on it, but with my luck the motor will grenade during the process and I'll never hear the end of it from the old guy. LOL.
 

LargeOrangeFont

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Thanks . . . I'm hoping it's not that . . . . I know it's a common deal on these motors. Since it has such low mileage for the age of the truck, I'm keeping my fingers crossed for a cheaper fix like LOF mentioned with the oil pick-up o-ring. I'm tempted to do a full sea foam engine flush on it, but with my luck the motor will grenade during the process and I'll never hear the end of it from the old guy. LOL.
40 on cold startup sounds a little lowish. you know what the hot oil pressure is at idle?
 

ltbaney1

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Thanks . . . I'm hoping it's not that . . . . I know it's a common deal on these motors. Since it has such low mileage for the age of the truck, I'm keeping my fingers crossed for a cheaper fix like LOF mentioned with the oil pick-up o-ring. I'm tempted to do a full sea foam engine flush on it, but with my luck the motor will grenade during the process and I'll never hear the end of it from the old guy. LOL.
hopefully you guys get lucky. let us know how it works out for you.
 

SBMech

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40 on cold start is really low. Get a mechanical gauge on there and watch it warm up. The gauge is NOT accurate and specifically built not to be.

If it's below 20 PSI at idle warm, the pan needs to come off and at least the pan/pickup 0-ring done, they split.

Specs warm are 6PSI min, personally if I see below 20PSI warm I am looking for problems.
 

Desert Whaler

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40 on cold start is really low. Get a mechanical gauge on there and watch it warm up. The gauge is NOT accurate and specifically built not to be.

If it's below 20 PSI at idle warm, the pan needs to come off and at least the pan/pickup 0-ring done, they split.

Specs warm are 6PSI min, personally if I see below 20PSI warm I am looking for problems.
Thank you for the feedback . . . when I get over there I'll start it up and report back.
 

SBMech

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If you want to learn something scary, buy three or 4 different brands of oil filters, then swap them after your truck warms up, there is usually a notable difference in pressure between them.

Considering the gauge is 20% or so inaccurate , any difference is sizable~!
 

Desert Whaler

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If you want to learn something scary, buy three or 4 different brands of oil filters, then swap them after your truck warms up, there is usually a notable difference in pressure between them.

Considering the gauge is 20% or so inaccurate , any difference is sizable~!
Copy that . . . I read somewhere that one of the filters (can't remember the brand) had an anti-drain-back valve that 'seemed' to help the problem of low oil at start up on these particular motors. They weren't claiming it was a cure of fix, but more of an 'aid'.
 

LargeOrangeFont

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40 on cold start is really low. Get a mechanical gauge on there and watch it warm up. The gauge is NOT accurate and specifically built not to be.

If it's below 20 PSI at idle warm, the pan needs to come off and at least the pan/pickup 0-ring done, they split.

Specs warm are 6PSI min, personally if I see below 20PSI warm I am looking for problems.
Agree fully with this assessment.
 

monkeyswrench

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Doesn't a factory 4.8 from 02 have the shorter skirt pistons still? Those were kind of the notorious piston rattle deals weren't they.
 

Desert Whaler

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Doesn't a factory 4.8 from 02 have the shorter skirt pistons still? Those were kind of the notorious piston rattle deals weren't they.
I'm not sure about the piston type on that motor.
It's always had a pretty good 'rattle' or 'tick' at cold start-up that normally goes away in under a minute. So I always thought that it just took a little time for oil to get up there and quiet things down.
 

Bigbore500r

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There’s a big difference between lifter tick, piston slap, and rod knock. Which one is it?

If it has a noisy lifter that shuts up after 30 seconds, it will probably run like that for a looooooong time. The early motors did this frequently till they redesigned the lifters and eventually all the motors ended up running the “LS7” lifter design which superceeded the older truck designs in everything.

If it has the infamous “piston slap” on cold start that goes away after a bit - it will also continue to do this and run for a loooong time lol.

If it has a rod knock...that’s a problem.
 
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Desert Whaler

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There’s a big difference between lifter tick, piston slap, and rod knock. Which one is it?
I'm not sure . . . I'm only mildly mechanically inclined on the basics . . . it sounded 'to me' that it went from being something like rocker arms ticking in the upper area that would go away a few seconds after cold start, to a 'knock' that lasted a few minutes before going away . . . but again I'm certainly no tech guy. It doesn't sound 'to me' to be piston slap.
 

Desert Whaler

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It goes in thursday . . .I'll report back. Thanks for all the great feedback ! 🙏 🙏 🙏
 

Desert Whaler

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Well . . . it hasn't made that sound since, and of course we couldn't get it to repeat the sound when I took it in. Guy at the shop says 'Run it and bring it back if/ when it becomes something we can replicate'. He didn't wanna tear into the engine to chase ghosts. So I dumped 6 ounces of Sea Foam in the crankcase, and put a double dose of Lucas Upper Cylinder lubricant when I topped-off his fuel tank. It's due for an oil change in about 300 miles, I'll do a de-carb just before that and see how things go.
Oil pressure seems like it's always been, around 40 psi at start up /idle . . . runs up to about 60 psi on normal acceleration.
Thanks for the advice here . . . If anything changes I'll update.
 

LargeOrangeFont

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Well . . . it hasn't made that sound since, and of course we couldn't get it to repeat the sound when I took it in. Guy at the shop says 'Run it and bring it back if/ when it becomes something we can replicate'. He didn't wanna tear into the engine to chase ghosts. So I dumped 6 ounces of Sea Foam in the crankcase, and put a double dose of Lucas Upper Cylinder lubricant when I topped-off his fuel tank. It's due for an oil change in about 300 miles, I'll do a de-carb just before that and see how things go.
Oil pressure seems like it's always been, around 40 psi at start up /idle . . . runs up to about 60 psi on normal acceleration.
Thanks for the advice here . . . If anything changes I'll update.
Change the oil pickup O ring and run it. Sounds like it’s nothing terminal.
 
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