Mechanical Noise That I Can’t Find.

[enjr44]

91' Ranger, 4L, Auto Trans, 4X4 - -

I have a mechanical noise that I can’t find. It sort of sounds like tappet banging away; but, it is not. It is a heavier noise than a tappet would make; but, not as heavy, as say, a main bearing. It occurs when the vehicle is cold and only happens after the truck has been sitting for hours.

The noise does not begin immediately upon start up. It takes about 2 or 3 minutes to start. The noise starts up, stops, starts again, stops again and gradually gets quieter. It keeps repeating is cycle until it is gone, completely gone. Sort of like something is not getting lubricated and then it is, and then not lubed again. Or as something it gets warmer it has less area to move around in. Each time noise starts it lasts for a shorter time period.

I have used a dowel to try finding it. Not in the heads, not from the bottom of the engine (oil pan or block). Not from the torque converter area. Not in the transmission. You just get the normal whirring noises for all of those areas.

It is a lot louder under the truck. And it sounds like it is coming from the right side of the truck around where first catalytic converter is located. I cannot pick it up with the dowel though.

Any ideas on what this could be???

Thanks, Ed

 

[enjr44]

Any one??

 

[adsm08]

Take the belt off and start it up. If it's stone cold your should be able to run it for 5 minutes before you have a problem with it getting hot. If your noise never shows up it is probably in the belt drive. I've had a few belt noises that made me think something in the engine was coming apart.

 

[enjr44]

Take the belt off and start it up. If it's stone cold your should be able to run it for 5 minutes before you have a problem with it getting hot. If your noise never shows up it is probably in the belt drive. I've had a few belt noises that made me think something in the engine was coming apart.

Pulled the belt this morning. Man it is quiet under the hood with the belt off.

Anyway, still has the tapping. It still takes about a 30 or 45 seconds for the noise to start. Still comes and goes. Still changes freq with engine speed; but, engine speed does not affect loudness or the starting and stopping of the of the noise. Just the frequency!!!

The noise gets progressively quieter with time. Still quits completely after say 10 minutes if you don't drive it. It also stops completely if you start it, let is sit for my normal 60 seconds and then drive it normal for a mile.

With the drive belt off the noise sounds like it is could be coming from the top of the engine. But, I can't hear it in the block, heads or valve covers. It sure as heck does not sound heavy enough to be a rod or main bearing.

Could an injector be this loud? Could a piston pin do this (but, it is not a double click)? Would a piston pin knock come and go? I can't think of anything that would wait 30-45 seconds to start knocking on a cold engine.

I still would like to find this and fix it (at least figure out what it is). I just do not think it is a rod or main. Any rod or main or piston problems I have ever had did not go away by warming up the engine.

Ed

 

[FritzTKatt]

Check your oil.

 

[adsm08]

Could be foot-balled push rods.

Oiling to the top of the push rods on the 4.0 isn't great, and they wear and can make a loud tick. Not sure if it could come and go and be intermittent like that, but I suppose it's possible if it's just starting.


Injectors can get loud too.

I've also seen the evap purge valve make a noise like what you describe, but the only time I saw that was on a 2010 6.2L.

 

[enjr44]

Could be foot-balled push rods.

Oiling to the top of the push rods on the 4.0 isn't great, and they wear and can make a loud tick. Not sure if it could come and go and be intermittent like that, but I suppose it's possible if it's just starting.

I can't discount anything, that is for sure. It sure is baffling me.

What is most baffling is that when cold it takes 30-45 seconds to start. What in the heck could be inside an engine that would not start making noise immediately upon cold start up? When warm it never makes any noise at all when started and driven.

Ed

 

[enjr44]

Check your oil.

Dumped 5.1 quarts in there last Thursday when I changed the oil and fliter. The noise was there before that.

 

[Road Angels]

Whats the mileage? timing chain noise at front of engine, piston slap if high miles

 

[martin]

It sounds like a sticky lifter. A stethyscope might be a good investment at this stage of the game, they're a bit more sensative than a stick in the ear.