Help with noises

[kyleag89]

Posted this on JF with no good respones..

 

Ok so my 4.0 is a 93-94ish and its making a tapping noise like it is a collapsed lifter. I took the valve cover off and inspected the push rods to see if anything is out of the ordinary but found nothing. This motor has 93K on it and the valves ard entire inside of the motor are clean. Oil pressure is 45 at idle when warm and it drives great.

 

This is no ordinary 4.0 tapping noise as it is very loud and constant. It does quiet down when its at 220 degrees but never goes away. Anyone have a suggestions on what it could be, I am stumped?

 

I used a pair of long nose pliers and carefully pulled out the lifters and inspected them. I then put them back in exactly how they came out. I rolled all the pushrods to see if they were bent. Torqued the rockers back down to 22lbs. So I can now rule out the head for any noises.

 

If it were rod bearings wouldn't it make it run horrible? The oils pressure is great and so is performance.

[Pete M]

have you tried a mechanics stethoscope to narrow down the source of the noise? or the poor mans versions, a long screwdriver or a length of tube?

[kyleag89]

Yes I have used a piece of hose, but it is still hard to pinpoint. It sounded like it was coming from the valves, thats why I took the head off and inspected.

 

Could it possibly be from the oil pump? I did have to swap my old distributor into the new motor, maybe I installed it wrong and made the oil pump make the noise??

[Pete M]

try a long screwdriver. :thumbsup:

[88pioneer]

cracked exhaust manifold :dunno:

[kyleag89]

I'm so stumped I am just going to drive it.. I guess I will find out whats making the noise when it breaks.

[JACKED88]

Is it a tick or a knock? Big difference in determining what it might be. You claim it runs fine but have you done a compression test?

[kyleag89]

It sounds more like a tick and not a knock. I haven't done a compression check on it, but I have a good guage so I will try that, what should I be looking for? I'm guessing obviously a difference between cylinders but also whether it holds the PSI?