JD730

This is on my 2000 24valve
I've been trying to trace this noise/knock I've been hearing for a while now (its been getting worse). Its loud around 1800 to 2000 rpms when its under power and I can feel something in the floor like a cylinder imbalance. Not as loud when I'm coasting, but something doesn't sound right.

I took the intake hose off and started the truck, I don't know if you would call it a knock, but its a sharp barking sound, very loud when I bring the rpm's up and has the same sound when I let it come back to idle.

I checked the valve lash and everything looks good. I need to borrow a scan tool so I can do a cylinder cut out with the intake open. Maybe this weekend.
I'm looking for ideas as the what this could be.
Loose valve seat?
Bad valve?
etc.
Thanks

thumper 549

cyl drop might help, compresion test might help ,
dose it do it with clutch engaged? or more under coast? more under load?? need more input

JD730

Clutch engaged/disengaged doesn't make a difference.
Noise is louder under load, but still audable under coast.

thumper 549

after cyl. drop test-if nothing shows......drop your pan (pretty ez) and look for some little green tubes in the bottom of the pan...thats the next ezest thing to do. (If your sure its not harmonic ballancer, inj.,clutch).

plow

jd730 any luck with your knock problem?

JD730

I've narrowed it down, The knock seems to be from #6, confirmed by a second reliable mechanic.
Fortunately I have an extra truck to run around with, so I've let this one sit till I figure it out. I'll probably pull that injector later this week when I get some time at home.

apache

I had a similar issue with my 93 12 valve. It was running warm but not overheating,running empty pushin uphill. Sounded like a valve out of adj but wasent,changed the injector,that not it. loosen the injector line to #3 and it goes away, no oil pressure loss. Noise wasent comming from crank area but up top under heads. All I can figure it was a wrist pin gone bad or broken ring. I drove it like this for some time and finally got rid of it. Good luck locating it and I hope its nothing major. Keep us posted.

RAM2940

If you think you might have been towing heavy or pulling a steep grade it is possible that the EGTs ran high and burnt the number 6 piston. Ive read several differant posts about number 6 getting burnt.

RCW

The best solution is to perform a compression check. If that shows low compression, then drop the pan and inspect the underside of the offending piston. Look for evidence of black burned-on coke.

If the compression is good, then check your injector on the knocking cylinder for a burned tip.

JD730

A little update:
I removed #6 injector, looked normal, not burnt.
I switched it with another cylinder to see if the knock moved with it.
I could not compression test it, but I did put 100psi of air into the cylinder I had injectors out of. I couldn't find anything unusual this way.
I put it back together and started it up, no knock for about 15-30 seconds. Then it starts knocking like it usually does. Still from #5/#6 area.

Has anyone had a VP-44 do this too them? or does this sound like an internal problem in the engine?

J BODY

Anytime I hear "noise from 6" it usually ends up being $$$. I had a truck come in like that once, but his complaint was "underpowered". With the intake lid off there was an audible "bark" (woof-woof-woof) sound while it ran. He just bought the truck, so he took it back to where it was purchased, so I never heard the outcome. Don't recall a "knock" with it, but there was a different "shake" to the engine at idle. Seems to me someone else had that prob here and found a bent pushrod. Keep us updated.

turbox2

If the intake was opened and you are hearing a barking noise that would lead me to think very strongly that you have some type of intake valve problem. just my .02 worth.

thumper 549

the interesting part is "no knock" for the 1 st 15 sec??....You start with no oil P. and get more....so maybe its not bearing related.....could be piston slap??

jrs_dodge_diesel

A great way to pinpoint the location of your noise is with a stethoscope. They sell the automotive variety at sears ( click here for the ad).



Another way to do it is do waht Haulin in Dixie did. He took a medical stethoscope and glued a metal rod to the diaphram. Works the same way as the automotive version.

BTW I have the automotive version and it works great. It helped me trace a dead cylinder on my old truck. (F150) took me all of 10 minutes to find the dead cylinder.

JD730

If it was bearing related it should have shown up in my last oil sample. As for the no knock for about 15 sec, I had gotten alittle bit of oil and fuel in the cylinder when I had the injector out, that would have calmed any piston slap down for a little bit. So piston slap is deffinately possible, under power around 2000 rpms it sounds scary, like its going to come apart, and you can feel it in the truck. I'm thinking maybe a burnt piston, but their should be noticable huffing out of the breather or could it be barly noticable? I've seen DT466's that huff smoke rings out of the breather at idle, but sound great and ran like you would believe down the track.

What ever is wrong with it, I think when the dust settles I'll probably have a 2000 with a '91 12valve in it.