I have a 2001 XJ with the 4.0 and auto transmission and around 90000 miles. There is a rattling noise from the engine, almost like a diesel engine sounds. It idles fine and seems to have plenty of power. I just put a new aluminum valve cover on and the rockers all seemed tight. Is there anything else I should check?

 

is it louder when your driving? consistent? or does it go away at highe rpms? might be a bad cam bearing which causes rod knock. Or bad lifters... I have it too... You most likely want to look into getting a new motor. your power and performance wont decrease by much but who knows how long you have till something fails. some motors have it and never die but i wouldnt push it. but to quiet down the noise if itslifters try putting in a touch of gear lube so you wont hear it.

 

It is difficult to hear from in the Jeep so I don't know if it gets louder. I mostly only hear it when it is idling and I am outside of it. I have added Lucas oil treatment to it but that did not seem to help

 

ok.. well you should be good. I have the same thing and i just got done with a wheeling trip this past saturday. it is most likely your valve train. just a few shot bearings is all. best to rebuild the motor really but like i said i have it and i did a trail ride. I just dont like the noise. its embarassing when you pull up somewhere haha

 

Check the torque convertor bolts. They are notorious for backing out and making contact with the bell housing causing a rattle or even a severe knock that is sometimes mistaken as a rod knock.

 

did the noise start right after the new valve cover? aluminum is an excellent sound conductor

 

The noise was there before the valve cover, I had one of my diesel mechanics at work look at it and he thinks it may be an injector issue. But he admits that all he works on is big trucks so he is no expert on gas engines. Does that sound plausible?

 

I am having the exact same problem with my 1995 cherokee sport, but mine makes the noise when i get into the high rpms when it is switching gears. mine started about a week ago after i replaced the head gasket.

 

Injectors do make a "click click click" noise as they cycle open and close. You could try and isolate the source with a stethoscope (long screw driver, handle to your ear, screw driver tip to supected source or a fuel line/vaccume hose ect.).

 

I have a 98 xj se with over 260k miles on it that I bought from my brother who had it for 7 years prior. I also noticed this rattling type noise and did some research. For one my brother has said it has been making this noise for well over half of the time he has owned and driven it as a daily driver yet hasn't noticed any real performance drop. I've also noticed that the noise is intermittent and that an oil change defiantly helps, so I now change my standard oil often every 2500 miles and every time I'm happy to hear the noise recede some... At least for awhile until it gets louder again.

I took it to my friends dads mechanic shop who has personally owned an Xj with this same problem. He said that these engines are notorious for lifters that wear down and cause problems with the valves opening and closing correctly(this causing a ticking/rattling noise every time the lifter pushes open the different valves) also since the lifters for these engines can't be adjusted (which most vehicles call for at least every 100k) they end up becoming loose and the steel-stamped lifters deteriorate from the constant pressure of regular operation. He's said that this can cause a decrease in gas mileage over time, and in worse case scenarios, a flattened lifter which would be an immediate problem but not necessarily a cause for a new engine.

He said to do a lifter replacement and full engine diagnosis he would normally charge around $500 (pretty good price) The thing is he also said that these lifters are much easier to replace than most vehicles. Instead of having to remove the engine head and really get into the engine to replace these lifters, it can be done by simply removing the valve cover and using a special tool called a lifter puller to remove the lifters and valves to replace them. He also said that this can sometimes never cause anything besides an annoying rattling noise and may never cause a flattened lifter as long as you don't drive it into the ground.

So in the meantime I'm looking into what it would take to change these crap lifters into roller-rockers. These would be way more efficient and would improve gas mileage as well. It wouldn't be too difficult to do in my driveway and the cost of roller-rockers today is way cheaper due to the improvements in CNC technology to cut these out of thicker high-grade steel.

 

I appreciate all of the advise. I am going to change the injectors and pull the valve cover again just to re-check everything for tightness and wear

 

it helps to know exactly where the noise is coming from. if you get a 3foot section of water hose and hold it to your ear you can move the other end of the hose to kinda find out exactly where the noise is coming from...

 

Actually with the 4.0 you have to remove the head as there is not enough space for the lifter to fit through.

 

Good point, I have the 4-cylinder and thankfully not the 4 liter. Although I wouldn't mind the extra power, these gas prices have me thankful for my little 4-banger.

 

What is your gas mileage? Just might be the next rage, swapping out 4.0s for the 2.5s!!