Baystate Jeepers

What I thought (assumed, hoped, prayed for) was an exhaust leak, is something more serious. The symptom is, after a cold start, my engine sounds great. (Maybe 'great' is a stretch, let's say there's no cringing or weeping when I start it) After 10 or 15 seconds, the tapping starts. Not bad, but its there. Then it gets louder. After ~30 seconds it probably peaks and will stay pretty loud for several minutes, and then it starts to quiet down. I don't drive it when it's loud, my usual approach is to start her up and let her sit idling for 5 minutes. After 5 mins or so the tapping noise is still there, but not loud. After driving for a while, it's barely perceptible

I'm thinking hydraulic lifter? Maybe? I want to fix it before it swallows a valve or throws a rod. I know this is a lot to ask for..... troubleshoot by imagining a noise..... but maybe this isn't an uncommon thing. I'm going to try recording it this weekend and post something

I need to keep this one going and if that means an engine swap or a new top end or a simple fix (simple fix..... that's funny!), that's what I need to do. Hopefully the mighty Jeep Jedi can enlighten me

What you described sounds like a lifter or lifters . The only way that I know to be sure is to start it with the valve cover off ! Precaution has to be made to stop the oil spray from going everywhere. I have layed a towel the length of the head on top of the rockers to it from getting all over. When you start the engine you will see the rockers ---rocking ! If you press down on them one at a time you will find the ones making noise. Press on the end with the push rod. Yes with your hands and no they wont hurt you. By now the oil should be flowing and yes there will be smoke. If you have a good amount of oil flowing and you have one or more of them making noise you have two options. Some people have said they have used an additive in the oil to help quiet them or unstick them. Some could only fix this with a high volume oil pump. As a rule of thumb , you never put new lifters on an old camshaft and vice versa. You could try that and it might work for a while but a scored cam lobe would eat the new lifter and be noisy again in a while. If thats the issue , changing the cam and lifters isnt wicked Hadh ! Last word on this is find a mechanical oil PSI gauge and test for oil PSI Vs. the dash gauge . Maybe the pump is going. Look at "Clifford Performance" If you decide to do a cam swap. You wont be sorry. "Melling" if you have to change the pump. If youve got a bazillion miles on her , it might be time for a STROKER ! You have a wonderful day FjR68

It sounds to me like your oil pump drive is failing on the end of the distributor (or oil pump drive).
For pre-05 TJs you replace it with a new Mopar oil pump drive. You also need to inspect the cam gear that drives it for wear. If the gear is worn out, put in a Clifford Performance (or other known performance company's) low to mid range power RV cam and lifters and pick up some acceleration and MPGs.

I sell a lot of these, they're new, but they fix the problem permanently on 05-06 engines. Item# 181468205737 on e-bay. It doesn't work for earlier engines, though, and it will require someone's high end OBD II scan tool to get the engine running correctly after it is installed. I would suspect you also will need to do the same diagnostic with your 2000. At any rate, Carl, the e-bay item will accurately describe why you have an oiling problem at start up. They just don't make this part to work on the earlier engine yet.

Thanks guys. What's really throwing me, is the noise isn't there when I first start it but I guess the residual oil from the last time it was run is still there..?... Mike, the fact that I always have good (~40 elbows) oil pressure when it's cold, the pump drive could be toast but still have good pressure?

I'll also pick up a mechanics stethoscope at HF. I'll do like you said Franky and if I don't find a wonky lifter / rocker / rod, I'll use the stethoscope to chase it down

It happens when the oil pump drive gear is dry from lack of lubrication. If you look at my e-bay item it should pretty much explain it and show why it happens.

On Jeepforum.com there is a 150+ page thread about it, and I we were the first offering this item for sale and I got calls from all around the country asking about it. Unfortunately, each caller seems to explain it a little differently and/or experience it just a little differently than the person before them.

Some engines run really, really rough - then all of a sudden work fine.

Carl did you ever sort this out?

No. Not resolved. I never lose oil pressure, it's where you expect it to be. It's not a mechanical guage but it responds pretty quick for what it is and it seems like a dry pump would have low pressure, and that would show on the gauge. Using a blend of mostly factory spec oil along with some Marvel Mystery Oil and another additive, I found a blend that just about made it go away. Not fixed, but masked, for now

It is the oil pump drive that clacks. Check out the e-bay link I posted above. I'll try to remember to e-mail it to you in case the number has changed. I don't have one for earlier models, though, they aren't making it yet.
It's not the lifters, it's not oil pressure - it will be the oil pump drive itself that has the oil leaking out of it during shut down and it takes a while to get oil back up in it. It damages the cam gear, though, and the cam should be inspected/replaced if needed. If it is JUST noise and not running rough you can probably get away with JUST the oil pump drive.
(The oil pump drive replaces the distributor on 4.0L with coil on plug ignition.)

My TJ has similar symptoms but i think it is piston slap. It starts 5-10 seconds after starting and goes away when the engine is up to temperature. When I disconnect the electrical plug to the injector of cylinder #2 it quiets down.


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