Topic: ZJ 4.0 Rattling/Knocking (Read 9198 times)

Brynjaminjones · « **on:** October 16, 2016, 07:26:58 PM »

Evening Birtys,

I'm having a bit of trouble with the ZJ that I'm really hoping someone can help with.

This past couple of days I've noticed that when revving above roughly 2800 rpm, the Jeep is vibrating much more than normal. It seemingly has nothing to do with road speed or anything else, only engine speed. Today it's become a little worse, to the extent that I'm completely avoiding revving it that high at all.

It seems fine (I think) at 1000-2500 rpm, but at a stationary idle there's now definitely more vibration than normal. By comparison my XJ seems as smooth as silk.

After paying attention to this for a while, Emily and I noticed whilst in traffic that there's a definite rattling noise coming from the engine bay. It sounds almost how I'd imagine a rattling cat would sound (maybe?) but is coming from the engine area. We've just got home and upon parking up found that the sound was quite loudly audible from outside the car.

Can anyone help me figure out what this is? It sounds bad enough to me that I'm a bit concerned about driving it further.

Further details:
- Noise is present in drive, neutral and park
- The rattling noise seems a bit random (not linked with an individual cylinder?)
- The vibration at idle is constant (doesn't seem random)
- All symptoms are the same on both petrol and LPG
- The Jeep has just had an oil change, but it was feeling rough at high revs the day before that
- Temperature and oil pressure are spot on
- Jeep doesn't seem to have lost any power

I'll post anything else as and when I remember. I also tried taking a video but it's not especially helpful. I'll post the link once it's uploaded.

EDIT: Here's a better video that I've just taken

donk498 · « **Reply #1 on:** October 16, 2016, 09:11:43 PM »

Possibly cracked flex plate?

bigjeepzj · « **Reply #2 on:** October 16, 2016, 09:32:28 PM »

or lose
link may help
http://www.cherokeeforum.com/f51/how-fix-flexplate-knocking-125547/

Brynjaminjones · « **Reply #3 on:** October 16, 2016, 09:33:34 PM »

Cheers guys, I wondered that too. I've just had a look at the flex-plate and as far as I can see all is well. The bolts seemed tight too, although I know that they often say you need to remove then re-tighten them. Would a loose/cracked flex-plate cause vibration at idle and high revs like I'm getting?

I've also just run it without the serpentine belt on and the noise seemed to still be present.

Brynjaminjones · « **Reply #4 on:** October 16, 2016, 09:38:48 PM »

Just in case it's of any relevance, the starter motor was replaced a couple of months ago; I've just read a couple of posts suggesting that the starter sometimes doesn't fully retract from the flex plate

Brynjaminjones · « **Reply #5 on:** October 16, 2016, 10:10:11 PM »

Here's a video of it running without the serpentine belt. After playing it back a few times I'm now convinced that the noise is at least a lot less pronounced without the belt.

Ged · « **Reply #6 on:** October 17, 2016, 12:37:12 PM »

Hiya the noise in the first video sounds just the same as my Cherokee and I know that is the power steering pump rattling.
that might be another line to look at, just a thought.

bigjeepzj · « **Reply #7 on:** October 17, 2016, 12:54:36 PM »

try unplugging the evap control unit

It will click like that if you have a problem with the fuel evaporation system

Brynjaminjones · « **Reply #8 on:** October 17, 2016, 01:24:25 PM »

Cheers guys, I'll have a fiddle later to see if that helps.
Just FYI, it's the deeper marble-like noise that's more obvious in the first video that I'm worried about, not the higher pitched ticking that both Jeeps have always done!

Sent from my HTC One M8s using Tapatalk

General Confusion · « **Reply #9 on:** October 17, 2016, 08:05:12 PM »

Might be worth taking a look at the engine mounts as well while you're crawling around.

Brynjaminjones · « **Reply #10 on:** October 17, 2016, 09:06:20 PM »

Why do I have such a habit of this... I'm such a moron.

The water pump is knackered! The bearing has failed, allowing the pulley to flop about. As there's a sodding great big fan attached to it that'll be why I'm getting bad vibrations too!

That's the second Jeep 4.0 in a row with a terminal-sounding "engine knock" that has actually had a dodgy water pump pulley!

I feel stupid but at least I can fix this

bgbazz · « **Reply #11 on:** October 17, 2016, 09:29:08 PM »

At least you will know where to start looking if it ever happens in the future.

Brynjaminjones · « **Reply #12 on:** October 17, 2016, 10:06:02 PM »

Quote from: bgbazz on October 17, 2016, 09:29:08 PM

At least you will know where to start looking if it ever happens in the future.

You'd have thought so, but I hadn't learnt from last time!

gazjeep · « **Reply #13 on:** October 18, 2016, 06:59:19 AM »

Practice practice & more practice young jedi

scrw · « **Reply #14 on:** October 18, 2016, 11:25:14 PM »

Quote from: Brynjaminjones on October 16, 2016, 09:33:34 PM

I've also just run it without the serpentine belt on and the noise seemed to still be present.

bgbazz · « **Reply #15 on:** October 19, 2016, 07:55:49 AM »

I'm not at all familiar with your motor, but doesn't the serpentine belt drive the water pump?

Just wondering.

Dave69 · « **Reply #16 on:** October 19, 2016, 09:04:15 AM »

and power steering, and alternator, and airc con pump

bgbazz · « **Reply #17 on:** October 19, 2016, 09:10:18 AM »

That's what I was thinking...so if the noise was still there with the belt off...??

JamesH · « **Reply #18 on:** October 19, 2016, 11:11:09 AM »

I suspect Bryn might have just been hearing the noise for so long and chasing so many different places that it got hard to tell when it was there and when it wasn't. I get to the point of hearing these noises in my sleep when the paranoia really kicks in

Hopefully the water pump will fix it, if not it's back to the stethoscope and worry.

bgbazz · « **Reply #19 on:** October 19, 2016, 12:50:29 PM »

You may well be right James...as I said earlier, I'm not familiar with this motor at all, but when he said that the noise was still there after he had run it without the belt, it got me wondering.

Whatever turns out to be the cause, I hope it's a cheap and easy fix.

Dave69 · « **Reply #20 on:** October 19, 2016, 06:38:22 PM »

Quite ironic that the water pump bearing has just failed on my CJ. Sounded initially like a failed hydraulic lifter but that may still be the case when i install the new pump in a couple of weeks

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Brynjaminjones · « **Reply #21 on:** October 20, 2016, 09:34:38 PM »

Quote from: JamesH on October 19, 2016, 11:11:09 AM

I suspect Bryn might have just been hearing the noise for so long and chasing so many different places that it got hard to tell when it was there and when it wasn't. I get to the point of hearing these noises in my sleep when the paranoia really kicks in
Hopefully the water pump will fix it, if not it's back to the stethoscope and worry.

Exactly the case James. Every time I over-listen to either of the Jeeps I'm guaranteed to hear something worrying. I have to continually remind myself that my XJ has been making all of these noises that would be worrying in most other engines for at least 4 years now!

I started Emily's Jeep with the belt off and was in such a panicked rush as the engine was up to temp and I knew the pump now wasn't operating, that I said "Yup, still lots of loud noises" and shut it off again!

Author Topic: ZJ 4.0 Rattling/Knocking (Read 9198 times)

donk498

Ged