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Discussion Starter #1
First thing first, I love my Jeep. Its a 98 TJ 4.0.
I sure hope it doesn't need an engine.

Symptoms
1. About two months ago I noticed that the idle would drop down low and I would need to rev it sometimes.. almost like cleaning it out. That got worse over time, but nothing too crazy. I just tried to reseat all the plug wires and put a new air filter in. Didn't change anything.

2. I replaced a clogged radiator about 1 year ago with what I remember to be a high flow radiator. Since then, My Jeep takes a long time to warm up to about 190. Seems really long, maybe 20 minutes. After it is warm, if I shut it off for 5 or 10 minutes, the temp drops down to about 150. Seems to fast of a drop, but maybe its just me.
My heat has been very low in the Jeep. Really sucks during the winter.
So, I replaced the thermostat, and no change there. There are no leaks in the coolant system and it has plenty of coolant. Not sure what the issue is. Tried to backflush the heater core and 'burp' the system. Still has the same symptoms.

3. About 3 weeks ago it started tick from what appeared to be the valve cover. I did not put a screwdriver to my ear to see where it was coming from. I could also hear the tick by the oil pan. I left it run like this for about 2 weeks. Then one day, when I was driving it, the ticking got quite a bit louder, like a diesel engine. So, I added Sea Foam spray to the Carb/Throttle body. No change.
So, I did some Googling and sounded like maybe a lifter. So, as a troubleshooting step, I ran some Sea Foam in the oil for about 150 miles, then did an oil change. Still no change.
I drove it like this for about a week and a half. Never keeping the idle over 1200 RPM.

NOW, I was on my way to take my Dad to pickup his brand new truck (Go figure) and while we were on the highway with LOW RPM and Hazard lights) I started to feel vibration in the steering wheel and the engine sound was tapping much louder. I knew something worse has happened. I pulled over and the tapping turned into what I would call a clapping/tapping/knocking. Not sure how to describe it. And, it does not want to idle very well at all. I pulled the Oil Cap off, and it has suction. Not sure why I did this.

I had it towed home because I'm now afraid to start it.

My hope is that its nothing major.

It would be great if someone could tell me what they think it may be and what type of job I am looking at.

I plan to troubleshoot more tomorrow. Any troubleshooting suggestions would be great.

Thank you all in advance.
 

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Pull the valve cover, if you don't find anything then you can assume that either it's major or it's not in the engine... ie flex plate, clutch, transmission
 

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:welcome: to the Forum..:wavey:
 

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Discussion Starter #4
What would I be looking for under the valve cover?
Would it help if I posted a video of it running?
 

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Based upon what you've described I'd guess it's something major.
 

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Discussion Starter #6
I forgot to mention, I replaced the clutch about a year and a half ago. The flex plate sounds like a possibility from what I've read. If it is that, can you replace it without pulling the tranny?
 

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If you have a clutch you don't have a flex plate..

Under the valve cover you would be looking for obvious broken parts
 

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Discussion Starter #8
Thanks all for your reply's.

I plan to pull the valve cover today to take a look.

Is there an easy way to tell if I have a broken piston or skirt?
 

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You can drop the oil pan and look. But that's a pain in the but because the exhausts is like... in the way.

Also I had a similar freak out a while back that turned out just to be my timing chain. Go on youtube and look at videos of a bad timing chain and compare that sound. get a mechanics stethiscope for a few bucks and listen to it.

I never had a vibration like that so it's possible it's much worse. But sounding like a diesel engine is exactly how my timing chain sounded when it started slapping the side of the timing cover.
 

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I had similar symptoms and didn't see anything after removing the valve cover. I dug farther and removed the cylinder head at which point I discovered a shattered piston.


Good luck.
 

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Pulling the exhaust is EASY if you know the secret

The secret is a sawsall and a band clamp... unbolt it at the manifold and cut it on the right side...

A band clamp puts it back together in seconds
 

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Pulling the exhaust is EASY if you know the secret

The secret is a sawsall and a band clamp... unbolt it at the manifold and cut it on the right side...

A band clamp puts it back together in seconds
I’d also check the cats. When mine failed I thought I toasted my engine with the clicking/tapping noise coming from it.
 

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Thanks all. Had my mechanic look at it. Sounds like a shattered piston due to lack of compression.

Thanks for all your replies.
I'd suggest slowing down a bit.... with some creative shopping and networking w friends you may well find a used engine and someone to help you get it swapped out way cheaper than the quote from your mechanic...

You're gonna lose your butt selling it with a blown engine.
 

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I'd suggest slowing down a bit.... with some creative shopping and networking w friends you may well find a used engine and someone to help you get it swapped out way cheaper than the quote from your mechanic...

You're gonna lose your butt selling it with a blown engine.
A re-manufactured engine is quick and usually the best course of action.
A good low miles used engine might be cheaper, but be sure to calculate the cost difference and decide on the most practical course of action.
The main question to answere there is "Are you planning on keeping the Jeep if you get the engine replaced?".

Simply replacing one piston is like sewing a patch on an old pair of jeans. You have a usable pair of old worn out jeans.

Good Luck, L.M.
 

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That said^
Replacing all 6 without pulling the engine from the jeep is VERY possible as long as you don't have cylinder damage...

Did it on a buddy's jeep about 50,000 miles ago and still running strong....

He had a few light marks in his cylinder that cleaned up with a quick hone job.... cylinder wear was minimal and he's thrilled with his $300 "rebuild" as he calls it
 

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As long as there is no damage to the block, shade tree engineering can save some $.
 
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Discussion Starter #19
This is a tough choice. I don't really have a bunch of time to try to repair this myself. I would think that if I did, I would want to maybe replace all the pistons. It looks like the piston kits are not that pricy. Has anyone else have experience replacing pistons without pulling the motor?
 

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Running it as long as you did with a bad piston [if it is a bad piston] The chance of no cylinder damage is remote. Low or no compression could be a valve train problem, so pull valve cover, look for broken parts then its off with the head to inspect. You might drain the oil and look for any sign of metal fragments in the pan.
Best of luck might be something as simple as bent push rod or total wipe out.
 
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