CommanderXJ

Okay, let me tear it down for you all.

My jeep has this weird tendency to knock after a fresh oil change. This same knock also happens to be there after every cold start. The knocking sound does not last for long, as once it warms up it goes away.

I have owned the car since 109k miles and she now has 116k miles. I have changed the oil a total of three times since I bought it. The first oil change, I put in 10w30 Castrol GTX with a Bosch oil filter. The second time I went up in weight to 10w40 Castrol GTX with a mopar oil filter. The jeep didn't like the 10w40 weight all that much. It idled kind of rough and it was difficult to start on cold mornings. On the most recent oil change, I switched back to 10w30 but I put shell rotella mated with a purolator pure one filter (gold plated oil filter). The car seems to love this oil much more as it idles smoother and drives smoother and the oil pressure is right where I want it to be.

Other than the aforementioned noise, the car runs and drives beautifully and very strongly. Its just the sound it makes when I fire it up in the morning sounds like a knock. And what's weird is that, after I put about 2000-2500 miles after an oil change, the noise on start up isn't as prevalent as it was when it was fresh.

Any ideas? I am stumped...I sure hope it's not signs of the motor going out....cuz I'd be pretty disappointed if the infamous 4.0 flaked out on me at only 116k miles


EDIT: I don't have a mechanic's stethoscope, so I can't verify the source of the noise 100% BUT...I can say that the noise seems like it's coming from the bottom end of the car rather than the top. I guess the range of it would be from the belts to the transmission bell housing....somewhere around that area. I don't know if that would help some.

EVcherokee

We need some numbers...where "do you want it"?

What's your oil pressure at on the Rutella? What was it at with the 10-40w?

Everything seems backwards, as oil wears, it loses it vicosity, so at 2,000-2,500 miles you should have less oil pressure, thus more knocking unless something else is going on. Going with a thicker oil usually stops or reduces ticks and knocks...Can you hear this knock when standing along side the rig or do you need to listen for it under the hood or oil pan? I've heard from alot of people that 4.0's have a natural knock, but you gotta get under it to hear it. Mine has had it for a while, and I've got just under 200K. I've used a long large screw driver to find ticks, knocks and squeaks before, just put the tool end on what your inspecting and put the handle against your ear(as far as "in" as it will got), sometimes you gotta press it in there, but it works. Be careful around the fan and belts though, a 18" long screwdriver flopping around has got some leverage. You could even use a dowel for that matter.

whowey

Actually no his sound isn't backwards.... For exactly the reason you stated... As oil wears its viscosity drops.. I would bet a dollar that he is experiencing a hydraulic lifter that is draining down. On cold starts the slight noise happens until the lifter fills back up with oil. So as the oil viscosity drops its pumps quicker through the galleries causing the noise to happen less or even not at all.

Commander... are you running any additives in your oil?? Some of them make the problem you are describing even worse.

firstime00XJ

Being new to Cherokees, and not having much experience with the inside mechanics of cars - is this also referred to as a 'sticky lifter'? Also, is this a huge deal, should the lifter be replaced or can it run like this for a while? To the OP: I have a lifter knocking on my motor, number 6 cylinder.

4jeepers

I get the same thing on my 99' GC on cold days or after oil service. Noisy lifter for about one to two seconds!

CommanderXJ

I have never run any additives in my oil. Just straight oil changes all the way through and through. I was thinking awhile back of substituting a quart of oil for atf and running it for maybe 500 miles and then changing it again but I didn't do it.


With the 10w40 the oil pressure was at a constant like 60 psi at idle and 80 psi under load. When I switched back to the 10w30, after the car warms up it goes down to around 40 psi and 60-70 psi under load. One of the reasons as to why I decided for a 10w40 change was to help reduce noisiness during start up but it was the same regardless. I remember when I got the car, it didn't make any strange noises on start up. THe oil that was in there didn't look old but for my peace of mind I went ahead and changed it the day I got it. I can't remember then if the motor started knocking on cold start ups or not.

I can hear the knocking just standing next to the car. But I can hear it the most at the lower end of the engine block.


EDIT: I also noticed that my oil pressure always seems to fly up to 80 psi upon initial start up at idle and then after about 20-30 minutes of driving, the oil pressure starts to drop to around 40 psi at idle. Could this have anything to do with it?

Kmart164

X2. Hydro lifters can be a cause of most things. In my shop class, we tore down 350's and rebuilt them. My groups engine had 3 lifters that would cause problems. 1 was a draining one, and we had 2 that were recessed, and that caused a slapping/knocking noise whenever the pushrod hit it. We had to take them apart and rebuild em.

It aint hard though. Soak them in a good engine degreasing solvent take out the retaining clip, smack them on a table until the inside slides back up to the top, then put the clip back in. And voila! Ran fine. No noises. And we got an A because we diagnosed it without the teachers help.

CommanderXJ

If it turns out to be a sticky lifter...is it something an average joe like me could replace?

Save for a few things, I have done pretty well so far on replacing things in the jeep. I have done most of the major repairs on it myself including transmission work, new radiator, new valve cover gaskets and so forth.

I am confident that I can do it, but I don't want to screw something up (but then again who does?) I have the FSM for this car too so that should help some.

Before I start tearing stuff down though, how can I tell for sure that it's a sticky lifter. And if it is a sticky lifter, would it cause the noise to happen towards the bottom end of the block as well?

EVcherokee

You got me confused Whowey, on your line of thought...that you get better oil pressure as it wears...wouldn't 5-w30(lower viscosity) give you better oil pressure from the get-go than say...20-w50(higher viscosity)? I see your reasoning, that the oil can move quicker at a lower viscosity, but if the oil galley isn't full in a few seconds, he's got worse problems. Although a higher viscosity moves slower, thats its advantage, it adds more "cushion" between bearing and moving parts, I've also noticed it helps pump up lifters that are stuck. Its like comparing water to honey

CommanderXJ...I agree that its a lifter, have you Seafoamed your motor? that right there may bust it loose. It sounds a little sketchy, but I've run one or two quarts oil and the rest ATF in motors before to clean out all the gunk and varish. Its a backwoods technique, but it has worked for me and friends in the past. Do it at your own risk, but if you do, don't rev it, and only run the motor till its warm, them change the oil, run it for about 15 min, then change the oil again. Don't be surprised if the ATF is black and full of slugde.

As far as replacing the lifter, its been a good 10 years since I rebuilt one of these motors, but I think you have to pull the head and they come out of the top of the block. When you pull the valve cover, look for a rocker arm that seems looser than the others, also there may be extra wear on the rocker arm, and top of the valve stem. I'd try to clean and repair the one you have instead of buying a new one, mixing or installing a new lifter is really hard on your cam and you run the risk of flattening a lobe. They make a special lifter removal tool, but success can be met with some long needle nose pliers, some thick wire or coat hanger and some patience. When I was a kid I had a lifter collapse on my truck, and I just used a junkyard lifter. It worked for a good 12K till I rebuilt the motor. You may just want to do a cam swap, doesn't have to be anything radical, you can stay stock if you want, it will set you back about $150

To answer your question, If you can pull a head, and reinstall it correctly, you can swap a cam kit/lifter, just do your homework and maybe have a buddy help/watch thats done it before. Free beer seems to get friends to help! Good luck!

CommanderXJ

I ran a can of seafoam through the brake booster line only and it was months ago. Quite to my surprise, the car smoked very little if at all.

As for the atf, what I will probably end up doing is maybe draining out a quart of oil (prior to my next oil change) and then put in a qt of atf and run it for about 15-20 min before draining it again and changing the oil. I don't know if I should be good by doing that route.

If I am going to do a cam swap, I'll probably go with a bit higher performance but I'll see.

whowey

Guess I wasn't clear enough....


In his particular situation...cold starts with a lifter that is leaking down...A lower viscosity oil will pump up the lifter more quickly. And the problem will be less. So as an oil starts to shear down.. its viscosity drops. That is why he sees the problem more when he first changes his oil. Higher end synthetics and diesel oils should shear down more slowly than mid market oils like Vavoline or Castrol. So it would be interesting to see the difference in this situation using the Rotella.

Bustedback

We have a fleet of Cherokees where I work. Just drive it and enjoy it, it is normal for these engines to make some noise. Your oil pressure is fine and normal. Why change the oil 3 times in 7000 miles? Every 6000 miles is fine for oil changes, you're just pissing money away otherwise. Now if you're driving only short distances and never letting the engine reach normal operating temperature, then you should change it more often.

cob24

so what is the ideal oil pressure on an xj 4.0?

CommanderXJ

I started to extend the intervals between oil changes. I am now going between 3500-4000 miles b/w the changes. I changed the oil a little earlier this time because the Jeep wasn't liking the 10w40 weight on the castrol, and plus I got a good price on the rotella so I went ahead and changed it anyway since it was about time to change it.

I do enjoy the hell out of this car, it's one of the best machines I have ever owned and I want it to last but I am just concerned about this noise at startup is all.

EVcherokee

I'd Seafoam your oil first, and take it from there. From what I can tell ATF is a lot more aggressive than Seafoam and I wouldn't use it unless your out of options. If your lifter is in the process of collapse, you need to do something soon or your valve train will get hammered to death, your rig will start to barely run, and be really hard to drive. Experience speaking

If your a DD remember that a lumpy cam is gonna give you more power, but will usually sacrifice mpg's and driveability. Also keep in if the cam allows for more air, but the intake, and exhaust don't, you will never see the full benefits. I've never cammed one of these motors, but one thing to think about is how the ECM will handle a change in lift and duration.

Whowey....I see where your comin from now!

Cob24....as far as I know 40 psi warm at idle, 60-75 psi under load is perfect, but I've heard of some 4.0's that go as low as 15psi at idle and they don't grenade.