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Unread 05-17-2014, 07:23 PM   #1
justincdst
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1998 ZJ 
 
Join Date: May 2014
Location: Sooke, British Columbia
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My not so new Jeep clap!

i have a 98 ZJ 4L with 319000km. I bought it a few months ago knowing there was issues but as a project to play with here on Vancouver island. I've also read up on hundreds of threads on this forum about piston slap and lifters knocking and all that jazz so for the new thread, I do apologize!

I dont have a lot of experience with jeep engines so Im having issues trying to figure out what is making my ZJ sound like a cross between a diesel and a tank. I've pulled spark plugs one at a time along with injectors hoping to isolate where the slap was coming from, I've pulled the valve cover to see if oil was coming up through the push rods (believe me there is). Ive pulled all the rods cleaned the rockers and springs and even tried a can of Wyns engine tune up. My next step was to pull the oil pan but my starter is fairly rusty and didn't want to tackle that today. I was going to pull the head but luckily didn't have the 13mm 12 point socket or a fuel line release clip... I do however have and engine stethoscope and decided to give it a listen.

I couldnt hear anything around the plugs around where the lifters would be, but it sounded like the knock was from lower down. So I checked around the flex plate and it kinda sounded ruff but not quite the right frequency. I happened to touch the exhaust off the manifold and bingo. So I probed around off the exhaust manifold and I can hear it straight through every cylinder, maybe a bit more around #1 but very clear through all cylinders. Again I don't have a lot of know how with these engines so what the heck could that be? Am I still looking at lifters or could it be a cracked manifold?

Unfortunately while I was probing around I accidentally punched a very small hole in the top of the radiator so I can only run the engine for few minutes at a time until I replace the rad...!!

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Unread 05-17-2014, 08:26 PM   #2
ZeeJay1997
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maybe an exhaust restriction, aka plugged cat?
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Unread 05-18-2014, 06:49 AM   #3
mrgimble
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I would still check the flex plate and the flex plate bolts.
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Unread 05-18-2014, 07:32 AM   #4
jnowak
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An exhaust leak can make that noise. Manifold around the collector are known.for cracking, especially if the motor or tranny mounts are bad.
Also the 4.0 do not have a very quite sounding drivetrain. Quite often, especially with the many miles, they will sound like a diesel.
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Unread 05-18-2014, 08:50 AM   #5
justincdst
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Thanks folks, I guess Im going to pull the manifold off tonight or tomorrow morning and Ill have look at the flex plate at the same time. The diesel sound is more of an understatement, sounds more like a John Deere! Since this is all new territory for me being converted to a Jeep, I just want to confirm I was trying to listen for anything coming from the lifters, it would be on the passenger side of the engine near the plugs right and pulling the spark or fuel supply to that cylinder would collapse the cylinder? just want to rule out any major engine repair on a 319000km engine.
Thanks again
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Unread 05-18-2014, 11:48 AM   #6
Oldfrog
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Both of my 4.0 engines ( 95 and 97) were bought new and they both sometimes sound like diesels at idle from day one off the showroom floor.
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Unread 05-19-2014, 04:29 PM   #7
justincdst
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Quote:
Originally Posted by mrgimble View Post
I would still check the flex plate and the flex plate bolts.
I checked the flex plate and bolts this morning. Everything there was honky dory. I guess my next step is going to be to pull the exhaust manifold have a good look at the collector.

Another question about that, wouldn't a crack in the collector fire off an engine code for something?

Last edited by justincdst; 05-19-2014 at 04:49 PM..
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Unread 05-19-2014, 07:25 PM   #8
jnowak
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Possibly a 02 code, the only true test is using a scan tool to read fuel trim, maybe a misfire. But usually it's just a clue not the actually problem.
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Unread 05-24-2014, 05:46 PM   #9
justincdst
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I pulled the intake/exhaust manifold off today and there is unfortunately nothing wrong with the exhaust manifold, no cracks anywhere and almost looks like a new unit. I guess what I was hearing with the stethoscope was just the valves working? Can they be noisy enough to make the jeep sound like that? I suppose since its already all apart next step is going to be to pull the head and fish around in there and if that gives up nothing pull the oil pan? While Im at it, anyone know any good tricks for cleaning out the intake manifold. I didn't think the intake could get that gunked up but she pretty nasty looking!
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Unread 05-25-2014, 01:29 PM   #10
Oldfrog
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Seafoam or spray carb cleaner will clean out that intake. Let it soak a while, then take a high pressure water hose to it. Just make certain it's 100% dry before reasssembling it. ( hair dryer)
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"..it's not air, it is the opposite of air... suckage so to speak."

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Unread 05-26-2014, 03:05 AM   #11
spur0701
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Quote:
Originally Posted by Oldfrog View Post
Both of my 4.0 engines ( 95 and 97) were bought new and they both sometimes sound like diesels at idle from day one off the showroom floor.

Ditto what he said, the I6 often sounds like an old tractor from the 50's.........
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Unread 05-26-2014, 04:48 PM   #12
coralman
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I just can't believe at 319 the exhaust isn't cracked. Its a miracle!!!!
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Unread 05-26-2014, 07:18 PM   #13
Gearhead31
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Quote:
Originally Posted by coralman View Post
I just can't believe at 319 the exhaust isn't cracked. Its a miracle!!!!
Majorly agreed!
Mine sounds kinda like a diesel between the drone of the exhaust echoing forwards, the constant ticking of the injectors, the light knock of lifter tick, and just the valves and other bits and pieces slapping around merrily about their way. Kinda reminds me of the 4 cyl 20 horse diesel tractor we used to have. That thing was a bloody beast and completely indestructible but my god I thought I had lost my hearing when I revved it up and the muffler blew out..
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Unread 05-26-2014, 10:36 PM   #14
justincdst
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I was pretty surprised about the exhaust myself. Even shut the lights off in the garage and shined a high powered flashlight into the collector end. No cracks. In all fairness though the hardware holding it all together was not as hard to come off as expected so i think someone was fishing around in there at some point and might have swapped it out. Ill get to the head this weekend and scrub out the manifold at the same time
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Unread 05-30-2014, 07:32 PM   #15
justincdst
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so i pulled everythin off to get the head off and it is one with the engine. I also dropped the number 12 push rod down the hole so it has to come off. Now I have the fsm for this jeep and checked online, everyone pulls the number 14 bolt with the head? I got all 16 out with no hassle? Any suggestions on how to pop the head out at this point? the only thing I didnt move was the ac compressor...
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