Help with engine sounds and rattling

skyzero

skyzero

Member
Joined
May 14, 2020
Messages
28
Location
Los Angeles
My 94 4.0/manual has been sitting in the garage for just shy of a year and a half after my transmission went bad. Finally got around to getting it all back together with a new transmission from Novak and using the LuK clutch replacement kit. While I had it apart, I also replaced the rear main seal, oil pan gasket, and oil filter.

After getting it all together, I threw in some gumout fuel system cleaner in a full tank of old gas and took it for a drive with a mix of city and highways. I don't think it had any loss in performance at least from what I can remember. After getting the tank half-way down I put in fresh gas. Shifting into gears feels smooth and no trouble at all. I used Castrol GTX conventional 10w30 for the engine oil and Redline MT90 for the transmission. After driving it, I didn't notice any leaks or seepage. Oil pressure goes up to the line just above 40 and when I'm stopped, it drops down to the first line (30?) below 40. It idles solid, no bouncing RPMs or anything like that.

Here are the sounds from the engine bay that have me concerned:

From the engine bay: https://drive.google.com/file/d/1UnO81lOv6yBZEcZ-ksuAz8mcfLVgXy-M/view?usp=sharing

From beneath the engine: https://drive.google.com/file/d/1m2oOcDRQeapz7Q1rkRK6GXDQNHea6Rvs/view?usp=sharing

Should I be concerned? Is this lifter tap or pinging? Could it be related to the fact it has sat there for over a year and there is some kind of buildup or gunk? I've read about people using seafoam, should I consider that? Should I consider changing the brand/type of engine oil? Could it be possible the old gas could be causing it as well? Am I making a big deal out of nothing? lol

Sorry for all the dumb questions!

There is also rattling and it sounds like from the muffler, but I'm not sure. I used the screwdriver method and checked spots from the oil pan to the muffler. It sounds like its coming from the muffler but I'm not sure it isn't because the muffler was vibrating against the screwdriver. Looking at it, it doesn't seem to be vibrating. The head shield doesn't seem loose. On the way home is when i noticed the "exhaust" rattling sound and it doesn't make that sound when I start up. It's most noticeable when reversing into my garage. Actually I might try reversing into the garage with my phone recording on the floor and see if I can get an example that way.

I've driven a total of 70 miles, 60 of that on the old gas. I checked the ODB codes and I got 3, one for the battery being disconnected (12), the other for no AC (33), and end (55).

Thanks for your patience and any help would be greatly appreciated! I need to get the jeep smogged this weekend so hopefully I can get it done and won't need to strip anything back out before then.
 
Last edited:
Did a bit more troubleshooting, the tapping sounds in the engine bay go away under load. I can only can really hear it when idle.

As for the rattle, doesn't seem to be exhaust related? I drove it around and it only seems to happen when letting off the clutch with no gas. When I give it gas I don't hear the rattle/shudder. Looks like it happens when i shut off the engine as well.

Here's a video of it: https://photos.app.goo.gl/TvLRFSPfRRMg2j978 You can hear more clearly at :01 and when I shut the engine off.
 
Last edited:
You'll have to fix the permissions on your files I can't see them without permission.

The rattling in the exhaust could be a few different things. The muffler has a series of baffles in there. If it's an ancient muffler, the baffles may have broken loose from corrosion.

It could also be the catalytic converter. Given enough age or bad contamination from oil burning, they can break apart. I've also seen them break loose from the housing. The brick was still intact but it was "loose" in the housing and was able to rattle. It took me a while to figure that one out lol. But give the whole system a look over for loose clamps, or bolts at the manifold/header collector.

As for your engine noise. Like I mentioned above, I can't hear the videos. But 4.0s are notorious for a few different engine noises. One is lifter tick. The lifters get gummy and don't pump all the way up. This can sometimes be "fixed" by a few short interval oil changes or trying out a HDEO like Rotella T. Another is piston skirt noise or piston slap. There's nothing to fix here. If the noise is skirt wear the skirt will eventually break off from the piston but it would be 10 years down the road.
 
  • Like
Reactions: skyzero
DOWNS said:
You'll have to fix the permissions on your files I can't see them without permission.

The rattling in the exhaust could be a few different things. The muffler has a series of baffles in there. If it's an ancient muffler, the baffles may have broken loose from corrosion.

It could also be the catalytic converter. Given enough age or bad contamination from oil burning, they can break apart. I've also seen them break loose from the housing. The brick was still intact but it was "loose" in the housing and was able to rattle. It took me a while to figure that one out lol. But give the whole system a look over for loose clamps, or bolts at the manifold/header collector.

As for your engine noise. Like I mentioned above, I can't hear the videos. But 4.0s are notorious for a few different engine noises. One is lifter tick. The lifters get gummy and don't pump all the way up. This can sometimes be "fixed" by a few short interval oil changes or trying out a HDEO like Rotella T. Another is piston skirt noise or piston slap. There's nothing to fix here. If the noise is skirt wear the skirt will eventually break off from the piston but it would be 10 years down the road.
Click to expand...
Thanks for the advice! I'll take a look at the exhaust system and see if I can find anything loose or anything. I've also updated the file permissions so you should be able to check them out now.
 
That rattle at the last 1 second mark after shutdown does sound exhaust related or rear transmission mount related. How did they look during reassembly? Lower oil pressure can be a sign of bearing wear. How many miles are on the engine? Is there much change in pressure readings between cold engine and hot?
 
DOWNS said:
Sounds like a pretty normal 4.0 to me.
Click to expand...
Thanks a ton for the confirmation!

Flyer58 said:
That rattle at the last 1 second mark after shutdown does sound exhaust related or rear transmission mount related. How did they look during reassembly? Lower oil pressure can be a sign of bearing wear. How many miles are on the engine? Is there much change in pressure readings between cold engine and hot?
Click to expand...

They looked ok, but I need to take a closer look at the mounts and isolators to make sure none aren't falling apart or loose. As far as the oil pressure, it only drops at idle to about 30, otherwise it stays solid at about 50. 137k on the odometer. There isn't much change in the pressure readings from cold and hot that I can recall. I'll take the jeep out later and keep an eye on it.

I've read about trying to pry the ax15 from the skid to see if there is any play in the mount, would that be something I could try to verify the mount is good without having to drop the skid plate?

On a happy note, I passed smog! :D

Also noticed a squealing noise when I was depressing and releasing the clutch earlier this morning, thankfully it turned out I just needed to add a touch of grease to the rod and rubber boot in the slave cylinder.
 
  • Like
Reactions: Flyer58
No offense intended, but you are driving a 29 year old vehicle. And a Jeep at that, it’s going to make some noise. I have always driven old vehicles and pay no attention to sounds unless the DB level gets pretty high.
 
ytradio said:
No offense intended, but you are driving a 29 year old vehicle. And a Jeep at that, it’s going to make some noise. I have always driven old vehicles and pay no attention to sounds unless the DB level gets pretty high.
Click to expand...
Oh yeah, totally get that. It's just been so long since I drove it that I forgot what sounds it normally made. Figured it would be good to get another person's thoughts just in case.
 
  • Like
Reactions: ytradio
to find noise, like this, no MP3 file actual noise posted, so you be asking the deaf, OK?
my last perfect engine build failed, (not the engine bad,and my work all) sounded like mains bad!
so i took a 2x4 and jammed it to the header pipe and frame and man handled it. (levered) and noise ended, my new header gasket was bad.(donut)
next engine, next noise (of late) have 50 years of endless stories. (cars and motorcycles and more)
I presume the noise can be made to happen parked, (the 10x more easy tests)

made huge sounds, like mains, ,but the last guy did not bolt down the A/C mount, only finger tight, got $5000 discount on this mint 2010 grand Cherokee
for 3 loose bolts and 1min. labor fix. 8 years later still runs like new.

we can drop all accessory belts see of noise ends on any engine, (like this) and run for 2min max from dead cold.
we will not let it overheat, ok, it is only a test.

for rebuilds.of any engine all bolts touched before now are then re-torqued to spec.
learn to use levers. to find noise. even lose suspension parts. levers cost nothing or bending them., (self)
I have 4 channel electronic , stethoscope, from STEELman that has saved me a fortune. micro phone clamps.

or go to a shop and ask the living to hear and find noises. it is a skill set, ive only touched lightly.

learn now noises telegraph, the noise moves through the metal and sounds come out of places odd, and wrong.
so we do lots of listening using my mic clamps and find the truth, even a collapsed HLA lifter or bend push rod can make a huge noise.
never assume the worst.
(10w-40 oil?) full up and never overfilled or it foams up and wrecks bearings.


good luck finding noises. , go easy , take your time,
 
Top Bottom