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What is making this sound?

2K views 19 replies 8 participants last post by  1026465 
#1 ·
http://www.youtube.com/watch?v=xlMSufSzR-4


My engine makes this sound up front down low, originally I thought it was a timing chain, so I replaced the timing chain (old one was very stretched), gears, and harmonic balancer. Still it makes the noise. Does it with the belt on or off. The cam nut does have it's little spring and plunger and the chain and gears went on fine (and much tighter than the old one) and I even used a new rubber guide. The balancer isn't hitting the case, what else is up there that can even make noise? Anyone heard this before?
 
#2 ·
It's real hard to tell from a recording. My YJ (4.2) sounds kind of like that, only not as loud. My best guess is valve noise. (You state new timing chain and no fan belt).

How is your oil pressure? Have you done a compression test and leakdown test?

You might try a part can of Sea Foam in the crankcase and the rest of the can in the gas tank. Read the instructions on the can.

Good Luck, L.M.
 
#3 ·
The fan belt is on in the video, but it makes the same sound with the belt off so it's nothing belt driven. Compression is all 150-160 cold&dry, more warmed up. Passed a leak down test. Oil pressure as indicated on the horribly inaccurate factory gauges with 10w30 is 45ish at first on a cold start which settles to a little above 20, it never dips below 20 but does go up closer to 40 while you're driving. Previous owner says it has a high volume oil pump.
 
#4 ·
Is it coming from the headlights? I note they appear misshapen....LOL...sorry
 
#12 ·
Try doing this with the belt off. ^^^

Have you tried the paper towel tube trick yet? Take the cardboard tube from an expended roll of paper towels. Put one end up to your ear and lean in toward the motor, pointing the open end at where you think the noise may be coming from. If you do this with the fan belt off, the fan blade won't interfere and you won't be in peril of being eaten by the fan blade. A length of heater hose will produce the same results.
A mechanics stethoscope is good to pinpoint some noises, but start with the cardboard tube to localize the noise.

Let us know what you find.

Good Luck, L.M.
 
#14 ·
I took the belt off and gave it a listen with various tubes and the stethoscope, there's nowhere on the block where it's especially loud, you can kind of hear it on the block just behind the timing cover on either side of the engine. Once you get near the front of the oil pan it's pretty loud though and especially scratchy sounding and is always there at any rpm. I wonder if a main bearing isn't starting to go. Considering that this engine has a few other non-related issues and I could use a new clutch I think I might be better off replacing the engine and keeping this one around to build up later.

There's a guy kind of near me with a 4.0 from a wrecked 97 cherokee with 150k on it that I bet I could get for around $200. That should bolt up in here without much hassle right? It's from an auto so I'd need a pilot bearing but apart from that all my old obd1 stuff should work on it right? My intake and exhaust manifold and belt driven stuff?
 
#16 ·
4.0 motor has hydraulic lifters. I don't think there is any adjustment.

TDodge7, from what I understand, the 4.0 long block assembly from an XJ is totally interchangeable with the long block from a YJ. Your engine accessories should bolt right up. Other posters may have more input.

Have you tried Seafoam yet?

Once you do an autopsy on your current engine, let us know what you find.

Good Luck, L.M.
 
#18 ·
Unfortunately since this is a 4.0 I'm unable to adjust the timing. Though in one of my other threads I get into how my timing mark jumps around at idle, vacuum flutters like crazy too, and I've got a pretty bad idle misfire. Surprisingly it feels pretty normal while you're driving.

I swung by the shop next to my old work and showed the Jeep to the owner today, he wasn't a ton of help, he heard the sound and said don't worry about it it's normal lifter sound, I told him about the timing and vacuum jumping around and he said not to worry about it. He heard the misfire and said the engine is out of balance because of carbon on the pistons and then told me to go get some 44k stuff to pour in the fuel. I remember why I do my own work now.

I have a bore scope, when the engine cools off I can look in the cylinders and see if the pistons and valves are covered in carbon. But the engine sound doesn't sound like any other properly running 4.0 I ever heard. And I've never heard of normal timing hopping around. And that misfire is still a mystery.

After I did the timing chain I tried a new distributor too and no matter how you indexed it it wasn't at all drivable, you could get it to idle as badly as it does now, but on the road it was nothing but flat spots. I even put the old cam position sensor into the new distributor and indexed it the same way as the old distributor and it wouldn't even start. I have the old distributor back in it now as that's the only way you can drive it.

I'm hesitant to just pull this engine if there's something dumb I'm overlooking and it's fine, but there's so many weird things going on with this engine that has me and everyone else stumped I don't know what to do. All I know is I have too much money in it to sell it not running properly for a loss, and I need to do something because daily driving my motorcycle for the last 6 months (rain or shine) has sucked.
 
#19 ·
I don't have a FSM for 4.0 6cyl. My Chiltons manual has a troubleshooting matrix for FI engines.

Perhaps you can find a FSM or a Chiltons or Haynes manual for the troubleshooting diagnosis.

I would fiddle with moving the distributor, even though you can't technically "set the timing". My timing mark jumps around and I have a slight idle misfire (carbureted 4.2). I just haven't installed my HEI yet. I expect it to cure both issues (hopefully). Can a HEI be fitted to a FI engine? You have already tried a different distributor. How sure are you that it doesn't have a fault?

If you decide to fiddle with moving the distributor, make sure to make a mark so that you can return it to it's current position if nothing changes.
Move it in small increments and keep an eye on your timing mark and vacuum.

Based on your statements, I strongly suggest following the troubleshooting matrix in one of the manuals before changing your engine.

Fluttering vacuum could be a bad valve. You state it passed a leakdown test. Were there any cylinders that were weaker or stronger than others? You state you are certain you don't have a loose or cracked manifold. How sure are you?

You may want to go buy the other engine, then pull your current pan and plastigauge the rod and main journals. If they are good, keep us informed. If they are bad, then swap the engine. I am beginning to wonder about your camshaft journals.

I will have limited internet access for the next week but will try to check in every couple of days. Keep us posted, we want to help.

Have you done the Seafoam yet? You may simply have varnish or some other crud causing your lifters to stick.

Good Luck, L.M.
 
#20 ·
I have a manual and I've gone through just about everything I could with the distributor and timing. The manual wants you to put cyl #1 at tdc on the compression stroke and index the distributor so that once the helical gear slips in the rotor is pointing at cylinder 1, but with the current distributor it will only run if you index it so the rotor is past #1 and almost halfway between #1 and #5. When I re-index the current distributor so that the rotor points directly to #1 the engine won't even start, it'll try but it never starts.

I figured the distributor must have something wrong with it because I know my timing marks are dead on at tdc and that I installed the timing chain/gears properly, I picked up a new distributor and installed it per the manual with the rotor pointing to cyl 1 and again it sputter and try to run but wasn't able to start. So I tried indexing it to the position the old distributor ran at and it would start and idle but at anywhere other than idle it was undrivable and had massive flat spots. I figured the cps in the new distributor may be a dud and tried the original cps in the new dist and again it would sputter and try to start but wouldn't run. So I switched everything back, put my old distributor back in with the rotor indexed to halfway between cyl #1 & #5 and now it drives again but still has that rough idle.

There isn't anything else timing related that I can change is there? One tooth more in either direction on the distributor puts the rotor on completely incorrect cylinders, the distributor can't be turned on a 4.0 to compensate. The computer has been to a computer repair place and they told me that the timing isn't programmable. But still it hops around at idle.

I don't have my numbers in-front of me, the compression tests were all 150-160psi cold and dry, the numbers went up slightly with oil and warmed up. The leakdown numbers were all within 5% of eachother and all in the "good" range on the gauge. No air from the intake, exhaust, neighboring cylinders, or radiator. I've also had the valve cover off and found no loose rockers or pushrods, broken valve springs, or anything else troubling. I even ran it with the valve cover off and everything looked perfect, it was oiling well too. This engine is only supposed to have around 20k on it, but since they decided to reuse that badly stretched timing chain I doubt they did that great of a job.

When I had the fan off I tried running the engine and poked an unlit propane torch all around the manifold and under it, when that did nothing I tried it again with starting fluid and brake clean. I've also tried blowing big puffs of cigar smoke into the intake
to see if I had any small leaks anywhere and found none.

Here's the sound with the belt off and the timing mark jumping around, it jumps more wildly towards the end
http://www.youtube.com/watch?v=NpV4gDK-2cQ
 
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