Is it possible to loose lifter preload while driving?

[6SENSE]

Some of you may remember (I have posted threads in this forum as well as the Hotair section) about the knocking sound that I developed when driving on the highway. Well, as the thread reads, "is it possible to loose lifter preload while driving?".

I have pretty much run out of answers. I have tried every test I could think of and have been in the motor to inspect and make changes of what I thought were the possible solutions. I finally brought it by two certified mechanics today to get second opinions. Both thought that the sound was coming from the front of the engine. Both instructed me to take off belts and see if the noise was still present. In fact one probed the sound to be louder at the water pump. I took off the belts and the sound was still there. I dont think the water pump could make any abnormal noise without spinning, right?
One of them did keep saying that it sounded like upper valve train, although it was a peculiar sound. He mentioned maybe a lifter preload issue, which leads me to my initial question. But if the preload was fine for the past 1000 or so miles since it was last apart, how/ why would it suddenly start knocking.

P.S. Dont know if this has something to do with it or not, but I have noticed for sometime that at times after I shut the car off, there is some weird knock sound that ittermitently goes for a small period of time
Also, let me know if more background is needed. Believe me, I thought I knew these cars, and this car, pretty well, and have tried just about everything .

 

[Steve Wood]

worn cam lobes will lose pre-load. Cam sensor can make noise. Stretched timing chain can make noise, and some cams/lifters can be noisy.

 

[Nick Micale]

You can lose lifter pre-load if there is not sufficient oil pressure in the galley. What does the oil pressure gauge read normally, and is it different when the noise starts?

 

[The Radius Kid]

The oil pressure thing may be right.
I remember a buddy of mine coming off the highway and losing pressure with a N/A Buick 6.
Turns out there was wear in the pump.
You might want to look at that.

 

[6SENSE]

Thanks for responses.

worn cam lobes will lose pre-load. Cam sensor can make noise. Stretched timing chain can make noise, and some cams/lifters can be noisy.

swapped cam sensors last night....no difference. Took out 7,000 mile GM chain and sprockets 2 days ago and installed new Rollmaster Dbl Roller....no difference. Cam is Speedpro 204/214 w/ Sealed power lifters. Tried swapping lifters....no difference. This is a knock that rises with rpm and gets rather loud (doesnt sound like bottom end though), and is definately louder than just noisy lifters/cam. Not so loud at idle though. Kind of sounds like the light tapping sound of a crank sensor improperly adjusted (@ idle). Sometimes you can barely hear it at idle.

You can lose lifter pre-load if there is not sufficient oil pressure in the galley. What does the oil pressure gauge read normally, and is it different when the noise starts?

OIL PRESSURE NEVER SUFFERED. Pressure cold is around 40 psi and 20-25 psi hot @ idle. This is the same before and after the sound came into play.

The oil pressure thing may be right.
I remember a buddy of mine coming off the highway and losing pressure with a N/A Buick 6.
Turns out there was wear in the pump.
You might want to look at that.

As stated above, pressure is great. Pump only had about 16,000 miles on it. I went ahead and stuffed some new gears in 2 days ago, since I had them laying around....no difference.

Told you, this sound is weird.....and driving me crazy . Let me think what else Ive done. took off each plug wire to take load off each cylinder....no difference. took off pan and cut open filter, didnt find much in the way of metal shavings or see anything abnormal. Checked torque convertor bolts. Checked for cracked rocker arm/shaft. Didnt roll them on a glass, but pushrods looked good (they were new, 1000 miles ago).

 

[Nick Micale]

Next simlpe thing to do is check the thrust bearing for wear, see how much the crank will move fore and aft.

 

[6SENSE]

Originally posted by Nick Micale
Next simlpe thing to do is check the thrust bearing for wear, see how much the crank will move fore and aft.

What is best procedure for checking this?

 

[Nick Micale]

Get a pry bar or large screwdriver and wedge the crank back by the flywheel and forward at the balancer. Make sureyou do NOT pry on, or contact, the ring on the back of the balancer

 

[steve hughes]

Didn't you say it sometimes makes noise AFTER the engine is shut off? If so maybe torque convertor. Unbolt the convertor from the flywheel, push it back the start it . See if the noise is gone.

 

[6SENSE]

1st off, thanks for the replies guys.
I pryed on the harmonic balancer a bit and it did not move at all. I didnt get under and take the flywheel cover back off though to pry the other direction yet.

Originally posted by steve hughes
Didn't you say it sometimes makes noise AFTER the engine is shut off? If so maybe torque convertor. Unbolt the convertor from the flywheel, push it back the start it . See if the noise is gone.

YES. It has done that for a long time. It was an off and on type of thing that I just stopped really paying attention to, although I wondered what the heck it was. Yesterday when it did it I definately noticed because it reminded me of the same type of sound that Im trying to chase down, just not as loud and frequent of course (because the engine wasnt running). I will try that Steve. Have you run into something like this before? Anyone?

 

[steve hughes]

I personally haven't had a convertor do that but have heard of it happening. The few times i have killed a convertor there was no doubt it was broke. That's the only thing left that could still turn for a second or two after the motor stops.

 

[6SENSE]

MORE CLUES

Okay engine gurus, Ive got yet another clue (I hope).
I was optimistic about the torque convertor idea, but that isnt it. WITH THE CONVERTOR DISCONNECTED, THE NOISE IS MUCH LOUDER AT IDLE! When I hooked it back up, the sound was quieter as before (can barely hear, until you rev the engine).

Also..... that light tapping sound when the engine is off started up while I was just turning the engine by hand to get to the convertor bolts! Im starting to believe that it has something to do with the whole situation. I would stop turning and the sound would just keep going for a little while, and it isnt the convertor because it did it with the convertor disconnected. I used a stethescope and it seemed more apparent around the top of the motor. WEEEIRD!

I checked the front to back play of the crank (thrust bearing). It moved at the most, maybe a 1/16", if that. Im saying I felt it move, but it was barely anything. Is that normal? Probably doesnt move at all once the convertor is hooked up?

Any ideas guys? Next course of action??

 

[6SENSE]

Anyone?? (look above ^)

If the sound gets louder without the load of the convertor/tranny on the crank, would that suggest maybe main bearings? Im just guessing here (thinking that without the convertor/tranny somewhat working as an anchor, whatever is loose is flopping around more easily), I'd really like to here someone elses ideas, as Ive been out of ideas for awhile now.

 

[MyWE4]

have you looked at the flywheel??
just a thought...they do crack and sound like a knock

I hope I am not repeating anything...I did not have time to read the thread very well...

good luck on the search....

Chris

 

[steve hughes]

If you have 1/16" end play you got big problems.End play should be around.004" to .013". If it's as much as you say then the thrust bearing is gone. Worn thrust will make some strang noises. I still don't see what could be makeing the noise after the motor stops turning. Without the convertor bolted up the crank is freer to move back and forth. Good luck.

 

[6SENSE]

Can thrust bearings be checked while engine is in car? Or changed for that matter? Or does this mean just go ahead and pull it out?

Thanks

 

[Crazi]

Yep can be changed with the motor in but you are in for a fun time. I did mine with the motor in and while it wasn't impossible, it would be much easier outside the car.

Take your time and be clean about it and you should be fine. I am actually going to redo mine soon. No problems, just couldn't find the bearings I wanted in there at the time and needed to get it done so took what the parts guy had. Had some bad transitional knock so I played it safe.

Now I have the bearings I want so I am going to spend another long day under the car... FM7144M I think...

 

[KEVINS]

I second the Thrust bearing. Pull the pan off and yank the thrust cap off and see what it looks like. Inspect the crank thrust surface also..

Good Luck!!

 

[y-hate]

I`ve been having a mysterious knock in my car for 2years,only when in drive and i thought it was the lifters or cam.. so after changing the cam 3weeks ago, still same noise... so determined to fine it , first try the harmonic balancer was hitting my cranksensor (lucky it did not break for 2 years)but this might not be your problem, but some thing to check if the noise sounds like its at the bottom end......:

 

[6SENSE]

Thanks guys.

y-hate, I wish it was the crank sensor hitting. It does almost sound like that at times @ idle, but it definately isnt. As soon as you rev the motor its much too loud of a knock to be that. It sounds like topend though, its weird.

I have no experience with thrust bearings and do not know how they sound when bad. steve hughes, you say that a worn thrust bearing can make some strange noises. Well this is definately a strange one. Guess I'll be checking the thrust bearings.
Those of you who have had bad thrust bearings before: can you describe the sound it made? Anything like the one Im describing?