4.8 Knocking

[mcrider]

I need your input: 2005 w/ 4.8 liter, oil and filter changes every 2500 to 3000 miles since new, quality 5-30 oil and ac-delco filters, never hot rodded or abused, extremely well taken care of. At 72000 miles, it developed a knock at normal operating temp, OK when cold. I can hear it under 2 conditions..... very light acceleration or starting up after sitting for 5 to 10 minutes. Oil psi gauge normal, even changed the filter to a Napa Gold, no change. It sounds like it's coming from the lower end but ???? This should not be happening considering the care it's had............any thoughts? Thanks

[Nytemare]

I need your input: 2005 w/ 4.8 liter, oil and filter changes every 2500 to 3000 miles since new, quality 5-30 oil and ac-delco filters, never hot rodded or abused, extremely well taken care of. At 72000 miles, it developed a knock at normal operating temp, OK when cold. I can hear it under 2 conditions..... very light acceleration or starting up after sitting for 5 to 10 minutes. Oil psi gauge normal, even changed the filter to a Napa Gold, no change. It sounds like it's coming from the lower end but ???? This should not be happening considering the care it's had............any thoughts? Thanks

Sounds like a rod man...or a wrist pin

2 choices here...inspect it or drive it till it goes

 

Inspecting it will cost you a pan gasket and a couple hours.

If it is a rod bearing...you can do a bottom end for about 500 bucks.

 

Pan gasket- 35 bucks

rod bearings- 25 bucks

main bearings- 90 bucks

front and rear main seal- 30 bucks

spinning the crank...you are looking at about 200...could be less.

This is all provided you know how to do this sort of thing...if not, have a shop inspect it...if its toast, get a new engine...they come with a 3 year 100K warranty

 

Sometimes bearings go for reasons beyond changing your oil regularly.

[mcrider]

I need your input: 2005 w/ 4.8 liter, oil and filter changes every 2500 to 3000 miles since new, quality 5-30 oil and ac-delco filters, never hot rodded or abused, extremely well taken care of. At 72000 miles, it developed a knock at normal operating temp, OK when cold. I can hear it under 2 conditions..... very light acceleration or starting up after sitting for 5 to 10 minutes. Oil psi gauge normal, even changed the filter to a Napa Gold, no change. It sounds like it's coming from the lower end but ???? This should not be happening considering the care it's had............any thoughts? Thanks

Sounds like a rod man...or a wrist pin

2 choices here...inspect it or drive it till it goes

 

Inspecting it will cost you a pan gasket and a couple hours.

If it is a rod bearing...you can do a bottom end for about 500 bucks.

 

Pan gasket- 35 bucks

rod bearings- 25 bucks

main bearings- 90 bucks

front and rear main seal- 30 bucks

spinning the crank...you are looking at about 200...could be less.

This is all provided you know how to do this sort of thing...if not, have a shop inspect it...if its toast, get a new engine...they come with a 3 year 100K warranty

 

Sometimes bearings go for reasons beyond changing your oil regularly.

 

 

[Zembonez]

Before you fall on the sword here... are you SURE it is a knock? These engines are know for going several hundred thousand miles without issue.

 

What you describe sounds like a wrist pin making noise... but it's hard to know here as I am sure you are aware. I'd have it listened to by a good engine builder (not a dealership mechanic). Good engine builders are many times better at diagnosing noises made by engines than the typical "fix it all" tech,

[mcrider]

Before you fall on the sword here... are you SURE it is a knock? These engines are know for going several hundred thousand miles without issue.

 

What you describe sounds like a wrist pin making noise... but it's hard to know here as I am sure you are aware. I'd have it listened to by a good engine builder (not a dealership mechanic). Good engine builders are many times better at diagnosing noises made by engines than the typical "fix it all" tech,

 

It sounds similar to the well known cold start piston slap in earlier Vortec engines except a little deeper in tone. Strange.......mine only does it when at operating temp

[Nytemare]

Yeah its always so hard to tell...most people think a knock is a knock...

 

But if it does it like he's saying it has to be one of the two....wrist pin...not much you can do but a total rebuild.

I could tell if I heard it...but it would likely have to be in person...cant really tell over shitty computer speakers.

 

Like I said...cheapest way to tell...and fix things if its a rod is to pull the pan...your out the cost of a pan gasket that way. But if you know someone in the area..an old guy preferably...they'll tell you whats making the noise.

[Zembonez]

My post was not insinuating that there aren't any good dealer techs... not at all. I was just saying that an engine builder has a tuned ear for this sort of thing. I know some damn good dealer mechanics... just wanted to clear that up.

[Nytemare]

My post was not insinuating that there aren't any good dealer techs... not at all. I was just saying that an engine builder has a tuned ear for this sort of thing. I know some damn good dealer mechanics... just wanted to clear that up.

Covering your ass Jim?

You are right....engine builders are best for things like this....especially the old guys.

Oh and so you know...I'm not a dealer tech at all man...I'm a navy weapons tech that fixes cars on the side.

[Zembonez]

My post was not insinuating that there aren't any good dealer techs... not at all. I was just saying that an engine builder has a tuned ear for this sort of thing. I know some damn good dealer mechanics... just wanted to clear that up.

Covering your ass Jim?

You are right....engine builders are best for things like this....especially the old guys.

Oh and so you know...I'm not a dealer tech at all man...I'm a navy weapons tech that fixes cars on the side.

 

A little maybe. Just looked at my original post and it didn't look to flattering. Good engine builders just rock!

[Nytemare]

My post was not insinuating that there aren't any good dealer techs... not at all. I was just saying that an engine builder has a tuned ear for this sort of thing. I know some damn good dealer mechanics... just wanted to clear that up.

Covering your ass Jim?

You are right....engine builders are best for things like this....especially the old guys.

Oh and so you know...I'm not a dealer tech at all man...I'm a navy weapons tech that fixes cars on the side.

 

A little maybe. Just looked at my original post and it didn't look to flattering. Good engine builders just rock!

 

Yeah...I guess it "COULD" have been taken that way.

And your right good engine builders are awesome...also hard to find sometimes...all the really good ones are either too busy...or gave up their craft long ago.

[alwcurlz]

I need your input: 2005 w/ 4.8 liter, oil and filter changes every 2500 to 3000 miles since new, quality 5-30 oil and ac-delco filters, never hot rodded or abused, extremely well taken care of. At 72000 miles, it developed a knock at normal operating temp, OK when cold. I can hear it under 2 conditions..... very light acceleration or starting up after sitting for 5 to 10 minutes. Oil psi gauge normal, even changed the filter to a Napa Gold, no change. It sounds like it's coming from the lower end but ???? This should not be happening considering the care it's had............any thoughts? Thanks

 

Should get it plugged into a scanner to find out the health of the sensors in the system. May be a sensor that is failing or maybe carbon covered giving a false feedback to the PCM causing an unwanted retard/advance in the timing. Could also be due to the fuel you put in it recently?

[mcrider]

I need your input: 2005 w/ 4.8 liter, oil and filter changes every 2500 to 3000 miles since new, quality 5-30 oil and ac-delco filters, never hot rodded or abused, extremely well taken care of. At 72000 miles, it developed a knock at normal operating temp, OK when cold. I can hear it under 2 conditions..... very light acceleration or starting up after sitting for 5 to 10 minutes. Oil psi gauge normal, even changed the filter to a Napa Gold, no change. It sounds like it's coming from the lower end but ???? This should not be happening considering the care it's had............any thoughts? Thanks

 

Should get it plugged into a scanner to find out the health of the sensors in the system. May be a sensor that is failing or maybe carbon covered giving a false feedback to the PCM causing an unwanted retard/advance in the timing. Could also be due to the fuel you put in it recently?

 

 

Maybe, but wouldn't I get a check engine alert for that?.........I did a search on this forum, lots of posts in regards to knocking, some do, some don't, no reports of engines grenading yet. In the meantime, the problem is easily aleviated by adjustment of the radio volume knob! Not ready to trade yet, still love it.