Engine tapping clicking noise that I am not hearing in the snow.

[Seawolf99]

I have a 99 2.5 liter wrangler. My engine makes a tapping/ slapping/ tick noise that is louder when your under the Jeep.
I have been chasing this noise for a long time. I was told it was the timing chain. And water pump. Those did not resolve it. It was louder at start up and would make the Jeep idle like crap for a bit. Now that it snowed and I am in 4 wheel drive I all of a sudden do not hear it at all.
Things I have replaced.
Timing chain
Transmission
Oil pan . Had big dent in it
Oil sending unit
Cat
Water pump
Thermostat
A lot of sensors
O2 sensors
Spark plugs from dealer.
It has a crack in the gas tank so I can only fill it half way.

Am I looking at a manifold crack? One guy said it was just noisy lifters and it will prob run that way for a long time. It was getting worse every day. Seems to be slightly better after replacing the spark plugs. I added an oil thickening agent that I used to use in my old truck. I can do basic things that just take logic but most of this has been done my a mechanic and nothing has changed this noise or idle issue beside the snow.

 

[RaymondT]

A mechanics stethoscope might help pinpoint it. They don't cost much. Exh manifold cracks are common but so is a noisy valve train. My 2.5 has a bit of noise on startup and the oil viscosity seems to affect it along with the outside temp. Timing chain, guide, and tensioner didn't change the noise.

I checked my piston skirts when I resealed the oil pan last year but that's one area you might want to check. Especially if you think the noise is louder underneath. Pan will have to come off so pick up a new FelPro gasket first. You can unbolt the exh pipe at the manifold flange to gain enough clearance to get the pan off. Some 2.5's have been known to have a skirt break off.

 

[billiebob]

Snow can absorb a lot of noise. The sound is likely still there. Driving on pavement beside a brick building or concrete guard rail will amplify the sound.

 

[Seawolf99]

I will call the mechanic that did the oil pan and ask him if he checked that when they replaced it and the sending unit. It was an extra $500 when I did my transmission so I was hoping that they would have checked everything. They needed to with the pan off. Would that cause the Jeep to idle funny at start up?

A mechanics stethoscope might help pinpoint it. They don't cost much. Exh manifold cracks are common but so is a noisy valve train. My 2.5 has a bit of noise on startup and the oil viscosity seems to affect it along with the outside temp. Timing chain, guide, and tensioner didn't change the noise.

I checked my piston skirts when I resealed the oil pan last year but that's one area you might want to check. Especially if you think the noise is louder underneath. Pan will have to come off so pick up a new FelPro gasket first. You can unbolt the exh pipe at the manifold flange to gain enough clearance to get the pan off. Some 2.5's have been known to have a skirt break off.