I have a 2000 Cherokee classic I bought from my dad (who bought it brand new in 00). It has 153,000 miles on it and I'm finally done with college classes for the semester and I've been getting ready to take my gf out camping. This also means I have time to try to get the Cherokee ready for some light off-roading.

Unfortunately:

Have been noticing a slight knocking noise (in addition to a ticking noise that's always been present) and its been getting worse. I did a oil change to mobil1 synthetic 10w-30 (from conventional 10-30) since the oil was on sale and it seems to make it louder. Took it to mechanic and he just listened to the engine for awhile and said it sounded like piston slap and to put conventional oil and zinc additive back in with heavier oil. I did this (10w-40 Valvoline oil, some hyperlube oil additive and hyperlube zinc replacement). The knock almost sounds worse now that the conventional oil is in there, but I cannot really tell. It seems to go away when RPMs go up but if it drops to idle it knocks. As RPM increases the knock seems to increase then disappear only to resume when RPMs fall.
Any ideas? I'm not a expert but I do have my parents garage and a basic set of tools.

 

Check this: https://www.cherokeeforum.com/f2/00-...118922/index4/

Generally, synthetics will bring out more noises in motors, and also have more advanced cleaner packages in them. It could be that it knocked enough crap loose which brought out the sound of the knock more. Likewise, if you have no leak, you may develop a leak or oil consumption after going to synthetic, and it goes away after switching to conventional oil/

I would read the thread I linked and do an analysis to determine if this may be your issue. Pulling thicker oil in is only going to act as a band-aid to your issue.

 

Thanks for the reply




I have had a cracked head which was replaced by the aforementioned mechanic. I blew a radiator on the freeway in rush hour and could not get over until I overheated. Apparently it was fixed by him and I haven't been using any coolant since the repair. Interestingly I got 4 new tires today and got to chatting with the Sears mechanic and he took a look at it and told me it sounds to him like the main bearings in the crank up above the oil pan. I had my stethoscope out last night and this definitely correlates to what I heard in the pan. I almost wondered if it was a flexplate, but I'll check that in the AM tomorrow. I will try to read more of your thread when I get the chance and trust me I've done hours of research trying to answer this myself, but since it's a "noise" its next to impossible to describe.

 

^
Why no mention of oil pressure?

 

Feel like a idiot for not mentioning oil press. I got to reading so many posts I almost imagined it in my post hahahaha. Oil pressure at cruise (hot engine) is around 40 and at idle it tends to drop to approx. 10-15 psi. On really hot days it drops to zero and check gauges light comes on.....this led to a serious panic a few years ago but I since found my gauge reads low, and when hot the pressure drops low enough to send the gauge to zero. Mechanic said his mechanical gauges read normal.


So I'm going to consider dropping the oil pan tomorrow to see if theres any debris. Keeping my fingers crossed.

 

Just did another oil change last night to Valvoline conventional 20W-50 and used K&N filter (HP-2004) and it seems to have made oil pressure a lot less variable. Knocking still there!!!!!!


On cold start this morning a odd grinding/screetch noise at crank?!?!?


Could really use some advice, if anybody has any clue what is going on

 

Loose flex plate bolts?

 

1. Get that 20W-50 out of there.
2. Put in 10W-30 or 10w-40
3. Check to make sure that this: http://midsouthjeeps.com/forum/topic...is-this-thing/ is not slapping the pipe below it.
4. Check flexplate for cracks and that the 4 bolts are tight.
To tighten the bolts use a large flathead screwdriver between the flexplate teeth to keep it from turning.

Since you have a 2000 and had head issues you probably have bigger problems.

 

Okay Mitch and MonacaYankee, I will inspect the flexplate first since you both mentioned that. If I can find any cracks in it I will take it to a trans shop to have them drop the trans and replace it. I assume heavier oil would put more strain on the flexplate which would cause the noise on cold starts like I heard this morning (assuming it is a bad flexplate or loose bolts)? I have heard the flexplate cracks are VERY difficult to see but I will do my best.


And MonacaYankee, thank you for that additional link you posted on the evap thingy, I will definitely check that out when I inspect the flexplate.

 

20W50 is just way over spec (to thick) for the 4.0. The oil would not cause any extra stress to the flex plate but the bolts being loose will. There is really no way of knowing what the actual problem Is until you start eliminating one at a time. Checking the flex plate out is the easiest.

I really don't think that the evap purge control valve is your problem though. It makes a quiet tick like a cracked exhaust manifold but much slower.

 

MonacaYankee, I agree that the evap valve is not likely since I have heard that ticking (slow) has almost always been a noise since I bought the jeep from my father. I'm going to pull the inspection cover in about an hour to check the flexplate and ensure everything there is hunkey dorey before I go any further.... I will post updates as soon as I can. Again, thanks for the reply!

 

And also I will try to get the 20W-50 oil out before too long...I forgot to mention that since you did say that it is WAY over spec

 

SOOOO....


I found a hairline crack (almost impossible to see!!!!) on the flexplate at the center of the plate. I could get my fingernail to get stuck in the crack by pushing on the plate and tweaking the plate. I have heard that a flexplate crack is next to impossible to see inside the vehicle, but this looks to be about a 1-2 inch long crack.


COULD THIS be causing the KNOCK????

 

Yes.

 

Thanks Scobar!


So I called a trans shop to give me a quote....don't have my parents garage for much longer today nor do I have a trans jack. Waiting for the call back