jcampbell99

My 99 has a knock. It only knocks when it is warmed up and only under load. I have pulled each spark plug wire and none made any difference. I have checked the torque converter bolts, they are tight. I am leaning towards a stuck lifter. Ok, here is my question, I hooked a mechanical oil pressure guage up to verify my dash guage. I have 24 psi at hot idle and about 50 under load. This to me seems quite good. If it were a rod bearing, would my pressure stay this high?

DFlintstone

I would tend to agree with you. Also a rod should quiet quite a bit with no fire. I had one.....I could hold the rpm at 1500 or so with (THE), wire off, then move the wire back to give spark and the knock was back.

You might take a good look at the crank pulley, they can knock when loose. Just the other day a guy probably had a broken crank between the first main and first rod bearing.

I believe he just split when he found what it was, so I'm not sure what it really was. Nice, Eh?

jcampbell99

It is weird because it sounds just like a rod but does not knock at all when cold. And when it warms up, and the knock starts, the valve noise is louder and uneven. I want to replace the cam but I just want to be 100% sure that will fix the problem since this is my DD and I don't have another car to use.

Zack92MJ

This is a stupid question, but how can you tell the difference between a knock and a tick? By volume?

jcampbell99

I always thought of a knock as a deep repetitive sudden impact while a tick was a higher pitch tap. When I worked on old v8s, this was easy to determine. But with these 4.0s with the cam so deep in the block, I am thinking a flat lobe or a stuck lifter can sound like a knock. At least that is what I am hoping.

Zack92MJ

Yeah me too

jcampbell99

I am really hoping that someone with more experience on the sounds these things make can tell me if a stick lifter can indeed sound like a rod knock. Just to let me know I am on the right track.

hawaiian808

make a video with your phone and post her up on youtube and then we may be able to help
rr give me a minute and ill do something for yah

jcampbell99

Here is a video of it.

When I am driving it, it sound like a lifter. You can't here it when it is idling, only under initial load when you first start off. Driving through a drive through is embarrasing!

hawaiian808

apparently he has piston slap


face palm



witch one does it sound like?

hawaiian808

you beat me to it

jcampbell99

Sounds the most like the first one

jcampbell99

Except it does not do it when it is cold. It runs best when cold.

hawaiian808

mmm so its coming from the lower end , does it go away while driving down the road/highway? if its a stuck lifter than run some penzoil ultra clean 5w-30 or rotella and maybe an engine flush to see if you can get clean up

jcampbell99

Yeah, I did that. Tried the marvel mystery oil and even duralube. It did get quieter but is still there. I can't find a good YouTube video where the sound is as deep. That is what makes me nervous. I am hoping it is a flat lobe slapping a lifter, I just don't what that actually sounds like.