Bad knock out of nowhere! Please help

[Basshead21]

A lifter sounds like a rod knock. I would bet on that if your oil pressure is good.

I really appreciate your help thank you. What are those like to change?

 

[wjburken]

I really appreciate your help thank you. What are those like to change?

If it is a lifter and you caught it in time such that it didn't damage your cam, you are looking at removing the intake manifold and the head on the side that you think the bad lifter is located and then replacing the lifter. If you guess wrong and took off the wrong head, you will have to remove both heads. At that point, you may as well just replace all the lifters. If the cam is damaged, which is a possibility, then you need to go much deeper.

 

[pwtr02ss]

I really appreciate your help thank you. What are those like to change?

Well, I haven't performed that operation just yet but I'm sure I will have to at some point in the because my avalanche has a lifter tick and about 2 months ago, I'm cruising up the interstate, two hour drive to catch a 5:30 am flight. Suddenly I heard what sounds like the blower motor rattling. Turns out it engine noise. I pull over about an hour from the airport and inspect things while my wife runs in the store to grab some breakfast. My plan was to drive it on until it quit (I figured it was gfailed lifter but it did sound almost exactly like a rod knock, on the rear section of the passenger side). Fortunately after about 5 min at idle, the noise went away. I limped it to the parking lot at the airport, never getting above 70 mph. Our return flight didn't land until 1:15 am on a Saturday morning so I was hoping it would get us back home.

After doing something thinking on my week long vacation, I decided that the o-ring on the oil pump must be bad for sure and the reason for the noise was a starved lifter. After letting it idle, it got the proper oil flow back and lifter noise went away. That being said, the way to test the o-ring is to pour 2 additional quarts of oil (if its full on the dipstick). That gets the oil level above the o-ring. I stopped on my way home and did that and ran 80-85 mph the whole way home without any noise. I've since driven it over 1k miles like that and haven't experience that sound again, just the same lifter tick I've had for the last couple years (and smacking at start up). My thinking is I'll just run it with 8 quarts of oil until something fails and I'll fix it then. For those who say to knot run it with extra oil, we ran our work truck like that over 200k miles (with the two additional quarts of oil because the o-ring was bad).

As far as replacements, I think you just pull the intake and heads off, replace the lifters and reassemble. Probably a bastard of a job but doable. I'm crossing my fingers that I don't have to find out for a long time.

 

[Basshead21]

If it is a lifter and you caught it in time such that it didn't damage your cam, you are looking at removing the intake manifold and the head on the side that you think the bad lifter is located and then replacing the lifter. If you guess wrong and took off the wrong head, you will have to remove both heads. At that point, you may as well just replace all the lifters. If the cam is damaged, which is a possibility, then you need to go much deeper.

Thank you again.

 

[wjburken]

Thank you again.

No problem. I had a lifter fail on my '07 Yukon XL with a 6.2 and had to replace the cam and lifters. I would bet if you asked, there would be a good number of folks on here that have dealt with a bad lifter.

 

[thompsoj22]

Well, I haven't performed that operation just yet but I'm sure I will have to at some point in the because my avalanche has a lifter tick and about 2 months ago, I'm cruising up the interstate, two hour drive to catch a 5:30 am flight. Suddenly I heard what sounds like the blower motor rattling. Turns out it engine noise. I pull over about an hour from the airport and inspect things while my wife runs in the store to grab some breakfast. My plan was to drive it on until it quit (I figured it was gfailed lifter but it did sound almost exactly like a rod knock, on the rear section of the passenger side). Fortunately after about 5 min at idle, the noise went away. I limped it to the parking lot at the airport, never getting above 70 mph. Our return flight didn't land until 1:15 am on a Saturday morning so I was hoping it would get us back home.

After doing something thinking on my week long vacation, I decided that the o-ring on the oil pump must be bad for sure and the reason for the noise was a starved lifter. After letting it idle, it got the proper oil flow back and lifter noise went away. That being said, the way to test the o-ring is to pour 2 additional quarts of oil (if its full on the dipstick). That gets the oil level above the o-ring. I stopped on my way home and did that and ran 80-85 mph the whole way home without any noise. I've since driven it over 1k miles like that and haven't experience that sound again, just the same lifter tick I've had for the last couple years (and smacking at start up). My thinking is I'll just run it with 8 quarts of oil until something fails and I'll fix it then. For those who say to knot run it with extra oil, we ran our work truck like that over 200k miles (with the two additional quarts of oil because the o-ring was bad).

As far as replacements, I think you just pull the intake and heads off, replace the lifters and reassemble. Probably a bastard of a job but doable. I'm crossing my fingers that I don't have to find out for a long time.

It's a good thing the LS is a windage motor, if the crank dips into an oil bath you will have foamed oil. Im amazed you can get away with 8 qt's as a norm but if it works it works! after you drive it at freeway speeds sometime pull the dipstick and see if it is clear oil or full of bubbles on the stick.

 

[wjburken]

It's a good thing the LS is a windage motor, if the crank dips into an oil bath you will have foamed oil. Im amazed you can get away with 8 qt's as a norm but if it works it works! after you drive it at freeway speeds sometime pull the dipstick and see if it is clear oil or full of bubbles on the stick.

Filling with 8qts is a temporary condition to get the oil level above the o-ring to see if that’s the cause of low oil pressure. I don’t believe he meant to keep it filled with 8qts.

 

[Basshead21]

Ok still bad knock and on my way home from work 2nd gear was sluggish.

 

[swathdiver]

Filling with 8qts is a temporary condition to get the oil level above the o-ring to see if that’s the cause of low oil pressure. I don’t believe he meant to keep it filled with 8qts.

He did. To my eyes, this is the first account we have of someone driving around for an extended period of time with 8 quarts and did not report any damage in doing so. Good to know!

Ok still bad knock and on my way home from work 2nd gear was sluggish.

Oil Pressure was still good?

 

[Basshead21]

He did. To my eyes, this is the first account we have of someone driving around for an extended period of time with 8 quarts and did not report any damage in doing so. Good to know!



Oil Pressure was still good?

It’s a little above 30 until you start driving then it goes up.