I have a 2000 jeep grand cherokee 4.0L, making a ticking/knocking sound , I am trying to figure out if its the lifters or a rod bearing out. I've taking it to one machanic and he says Rod because it sound like the sound is coming from the bottom of the motor, but I know in the 4.0L that the Lifters are in the middle of the motor so that could sound like the bottom??, my husband tried to push down on the valves but said he couldn't tell if that made a difference so I am hoping some one can give me a way to test it out so I can make the choice between just changing the lifters or having my motor rebuilt. Thanks

 

How many miles on it?

Could be cracked flex plate, loose torque converter bolts, rod bearings, or the valve train not torqued correctly. I would inspect in that order and you dont have to overhaul the whole engine for rod bearings, you can leave the crank in the motor while its in the jeep with the head still on if it comes to that, i doubt it but ive done it that way

 

185k miles on it.

 

Whats the oil pressure at? ...Tj

 

O and welcome to CF from Tj...

 

185k, prolly the lifters then. They start rattling around 160k. If the oil pressure's good, thats prolly it

 

Does it increase with rpm? Does it go away once warm?

 

where'd you hear they start rattling around 160k? I've had 1/3 jeeps make noise under 190K, my current has 212K and is the quietest 4.0 ive ever seen/heard (probably due to sludge). While it may be annoying it doesnt mean the motor will crap out on you.

 

the oil pressure stays normal and the sound quites a little after its warmed up, but the ticking accelerates with the throttle...

 

yeah increases with throttle and only quites when warm never stops.

 

Sounds like a rod bearing to me. Check the flex plate bolts as mentioned, they are known to loosen up over time and can create a noise similar to rod bearings.

I would drive it 'till the bottom end comes apart and then swap a used or rebuilt engine in. Only down side is if a rod lets go it will make a nice size hole in the block. Used engines are cheap on Craigslist.

 

Broken rods dont "always" put a hole in the side of the block, it depends on where the rod broke. Fixed a YJ with a hydrolocked motor that broke 1 rod and bent another in 3 planes. I couldnt believe it ran it the bent rod as well as it did after we dropped in another piston and rod.

 

Semantics.

 

Welcome to CF!
I hate noises... Check Youtube. Search "Jeep Knock" Every noise you can imagine is on there. It is a really good comparison as far as narrowing it down. Hope it's nothing serious. Good luck!

 

My sister is having a similar problem with her 2000 xj. She was told it was rod bearing so I changed them for her. I also did the oil pump while there. But it still knocks or ticks. We did not do the main bearings. My sisters motor has 184k too. The sound on hers sounds like its in the bottom at the front. Like near piston 2