Nobody_Special

Okay everyone... I've searched high and low on my issue and have not found the answer yet, so maybe someone can point me in the right direction, or help me solve my problem???

A few weeks ago my Jeep started making a squeaking noise... not real bad but a mild "squeak, squeak, squeak, squeak, squeak..." once the engine was warm and I had been driving it for several minutes. I assumed it was the water pump just starting to go. Since it wasn't a horrible squeak and there was no other obvious signs of trouble, I blew it off until Thanksgiving when I had the time to really look into it and tear it down. Well, I took off the belt, the pulleys all seemed tight and smooth and so then I listened closer it sounded like the squeak was coming more from the center of the engine rather than the front. I put everything back together and drove it through the weekend trying to "feel" what was going on... I started to fear the worst...
I've been searching the internet for someone else with similar symptoms, but their squeaks are when the engine is COLD and go away when the engine was warm... my symptoms were the opposite. I changed my oil, as it was due for a change anyway, and that seemed to quiet the squeak some, but it was still there. I had read several posts about other people's distributors going bad, so I touched mine and felt a light thump or tap on the cap with each squeak I heard. I thought I had tracked it down so I bought a new distributor and installed it tonight... No joy... I still felt the thumping in the new distributor. Since the old distributor showed no excessive play in the shaft or bearings and really almost no wear at all, I pulled out the new and put my old distributor back in.
So... I am totally clueless as to what could be going on and really need some help on this. I love my Jeep and have had it almost forever. I want to keep it forever, but am financially stretched really thin right now, so if the engine "goes", it will be sitting in the driveway for a very, very long time.

Some more background on my Jeep:
1990 Cherokee Pioneer with 4.0 and Auto trans
Total mileage is 256k, but put a new engine in it about 9 years ago at 188k
New water pump about 18 months ago.
New Alternator and serpentine belt 6 months ago.
I had 2 injectors replaced about 8 months ago, the rest are original I believe.
Oil changes are always on time.
Checked the motor mounts and they seem tight.
Engine runs a tiny bit rough, but really not that bad... (probably the other 4 injectors getting flaky???)
My "New" engine only has 70k on it, so I hoped it was not something internal, but suppose it is possible.
I tried a new distributor tonight and it made absolutely NO difference.

The thump (or tap) I feel in the distributor is very consistent, and increases / decreases with engine speed and it is there whether the car is in park or neutral. Thump does not appear to go away, regardless of temperature, but squeak only appears once engine has been at operating temp for several minutes... (about 20 minutes from a cold start)
The best way to describe what I feel when I put my hand on the distributor is: It feels like a little man with a hammer is inside the distributor and banging on the inside of the cap... "tap, tap, tap, tap, tap..."
Touching other parts of the engine, I do not feel the tap as strongly.

Please help... I am scared to death that I am going to blow my engine if I drive it much more, and I don't have the cash to take it into a shop and have them tear the engine apart.
I can provide much more info and/ or photo's if needed. Tell me what to check or try and I'll do it...
Thanks!!!

Nobody_Special

Took the serpentine belt off the engine and it made no difference in the feel.
All the pulleys turn smooth and without resistance. Checked to make sure all 6 cylinders were firing and they are... still feel a light thumping or tapping when I touch the distibutor... :-(
Also, the tapping increases in frequency and intensity as the engine speed increases.
Now I am really scared...

Haven't driven it far enough to get the squeak to start up again, although the oil change may have helped that slightly (???). I'll take it for a long drive this weekend to see if the squeak comes back, or if it's just the thumping tapping that remains.

van island

the squeaking and thumping is the top bushing of the dist' it is common for them to do this over time. I see this lots ( I am shop foreman/ tech' at a jeep dealership) remove dist' drive out pin, clean shaft,soak in cleaners to disolve grunge, pull out entire shaft, clean shaft and bushing, lube with oil or light grease .and reassemble.or buy new one. Eric

Nobody_Special

Thanks for the reply... I did try a new distributor, but the symptoms did not go away. Noise and feeling with my hand on the cap was identical to the old dist. I did manage to get rid of the squeak by changing the oil and using 10w30. It was due, but not overdue for a change, and when I took it in for the last change I think they used 5w30. Seemed strange, but I have driven it for several 1 hour trips now with no squeak. Thump is definitely still there though, and has me concerned about a major failure.
Could it be something with the camshaft, or the oil pump? They are both right in the same area as the distributor, so maybe the thump is just traveling through it to the cap? I looked at everything I could see through the hole when I removed the dist, and everything looked okay, but could this be a bearing or something on the camshaft going, or would that be a much faster thump than I could distinctly feel?