Knocking sound

Jacob Wooding

Jacob Wooding

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Joined
May 14, 2018
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18
Location
Halifax, VA, USA
So for the past week or so my Jeep has had a slight knocking sound(like a stuck lifter), until today...... while going down the road minding my own business not driving hard or anything out of the ordinary. it stopped for a split second, then there was a rattling noise then it just died. i tried roll starting it and nothing. i tried to start it again and it attempted to run for a few seconds but it sounded like it was trying to run off of maybe 2 or 3 cylinders. what could this be? and if it helps any she has about 189xxx miles and is a 02 sport. no prior problems and i use good oil and filters. also never saw any metal in the oil in and i changed it about 750 miles ago. completely lost at this point and any help is greatly appreciated
 
Sounds potentially serious but impossible to know what the problem is at this point. A mechanic will likely start with a compression check but I'm guessing a significant lower-end problem inside the block. Good luck on it but without having heard the problem, this is just an uneducated guess.
 
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X2 to what Jerry said. It sounds very serious!

I’d start by doing a compression test.
 
maybe the timing chain jumped a tooth. I don’t believe that the 4.0L is an interference engine, so that wouldn’t be too serious. However, you need to do a compression check anyway.
 
Well just thought I’d update, as of tomorrow morning Jeep is off to the shop to have the motor rebuilt... 2 broken connecting rods 1 cracked piston and 6 bent/broken valves.
 
Wow, that sounds like some pretty serious carnage! I wonder what let go to cause all that?
 
Last edited:
Jacob Wooding said:
Well just thought I’d update, as of tomorrow morning Jeep is off to the shop to have the motor rebuilt... 2 broken connecting rods 1 cracked piston and 6 bent/broken valves.
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Wow! How did all of that happen? The 4.0 is a non-interference engine.
 
Not exactly sure what happened first, or really how it happened honestly. But i found a great local engine builder and hes going to tear it down and rebuild it. does anyone know anything about 505 performance? He had mentioned getting a mild cam and the pistons and connecting rods from them.
 
Also I know the guy that i bought it from and he had all the service records for it from the dealership he bought it from. Oil was changed every 3000 miles and he actually got them to do a tune up every 20,xxx. It has always been very well taken care of so i cannot see why it would happen. Since i bought it i have used Royal Purple HMX and changed it every 3xxx. I have even changed all the gaskets, fluids, and seals from the valve cover to the diff. I dont have any aftermarket performance parts or anything. So honestly there is absolutely no reason it should have happened.
 
Jacob Wooding said:
Also I know the guy that i bought it from and he had all the service records for it from the dealership he bought it from. Oil was changed every 3000 miles and he actually got them to do a tune up every 20,xxx. It has always been very well taken care of so i cannot see why it would happen. Since i bought it i have used Royal Purple HMX and changed it every 3xxx. I have even changed all the gaskets, fluids, and seals from the valve cover to the diff. I dont have any aftermarket performance parts or anything. So honestly there is absolutely no reason it should have happened.
Click to expand...
Also have a knocking 02 sport...been discovering piston slap is common, apparently. Now i’m worried. How did the rebuild go?
 
Does 3xxx mean 3,000? If so, why xxx? Curious.
And I would imagine that some of that damage was cumulative. The odds of all that getting wiped out at once on a non-interference engine is slim. Probably started with a slightly bent pushrod or two and continued until the end. I had a 258 in a CJ-7 that had the distributor turned a good 30* to 40 * off tdc. And it still ran! Actually if it wasn't for the power loss up hills I would have never noticed it. The ability of an inline engine to keep running is amazing.
 
The rebuild went great, took about 3 weeks because the shop was backed up. I had to take it back the other day the water pump gasket blew out somehow. And yes I’m assuming it wasn’t all at once it just stopped completely all at once haha. And yes the 3xxx is 3000 I always change oil right around 3000 but hardly ever exactly on it therefore I used the 3xxx.
 
Curious, what did they think the cause was ? age & fatigue ? or something else ? 200K is a lot of miles .
What was the approx cost ?
 
The guys said that it was more than likely from over-revving, but she has never seen more than maybe 3500rpm so I have no idea. And I think the total rebuild was 3250ish but that was with a slightly better cam, fuel rail, and injectors. If I had gone plain Jane basic stock rebuild they said it would have been between 2500-2800.
 
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