Recently purchased a 1987 Jeep Cherokee Pioneer with a 4.0. Jeep ran well upon purchase but had sat for a little while. I have done a lot of routine maintenance stuff to it in the past two weeks (new thermostat, serpentine belt, water pump, fuel filter, oil filter, air filter, spark plugs and wires, master cylinder, shocks and probably some things I'm forgetting)

and during all of this.... I got the oil changed.

Ever since I changed the oil (about 3 days ago) there is a constant and consistent "whir" coming from the front end. You can hear it from the outside of the jeep and in the drivers seat but it is less noticed in the passenger seat. The noise remains the same upon acceleration. Does not get louder or softer or change pitch regardless of what you are doing. Everything is running perfectly otherwise and certainly has a bit more get up and go since the tune-up.

I am concerned this oil change might have loosened something up? Bearing? Maybe I need a thicker oil? (Currently using 5W) Are there any oil additives that you like to use for the inline 6?

HELP??

 

The book calls for 10w30.

 

Oil weight will not make a difference unless you put SAE10 or SAE 60 in there.

First things first: remove the serpentine belt and start the engine. Do this when it's cold and not for long as the water pump won't be moving (nor will the alt). This will help you determine if the noise is caused by a pulley. You can also use a short piece of hose to listen and pinpoint the exact source of noise. While the belt is off, an engine not running, turn all the pulleys by hand and check for grinding, wobbling, etc.

What did the oil look like when it came out? Any sludge under the oil filler cap?

 

x2. The belt could be contacting a shroud or even the newer water pump sounds different than the old worn out one.

 

Is it the electric fan?

 

So I noticed the dipstick was reading a little low (slow leak somewhere) so I added another quart and it significantly decreased the noise. The oil was jet black but not particularly sludgy when it was initially changed and no metal was found in the filter or anywhere else for that matter so Im hoping all internal components are cool. I was thinking I was going to change the oil again soon anyways since it obviously hadn't been done on a while so I want to really make sure I got all the old stuff out. I did read more into the oil type and will most likely go with 10W for the remainder of the summer (though I have also read that this is not so much of an issue... I figure why not err on the safe side)

The trans fluid looked beautiful and full as well.

Since I work like a dog the serpentine pull will have to happen Saturday but I fully intend to get on that asap.

Also planned for saturday is a check up on the differential as well as bleeding of the transfer case and linkage check since I have not gotten a chance to go over these thoroughly.

Thank you for your help so far. The resources (people) on the forum have been great! I will be sure to keep you posted.