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[Brynjaminjones]

The Wagoneer has developed a lovely little knock that I'm trying to figure out.

The water pump shaft had some good play, so that's been replaced.
All seemed well, but the knock is back again.
I noticed it a week after our first oil change, to 20W50 Valvoline VR1 with a Wix filter.


-It's only noticeable at idle and just above
-It speeds up with the engine
-It sounds (to me) like it's at half crank-speed
It's done a few hundred miles and gotten no worse.

Here's a video from today, immediately after driving for 75 minutes:





P.S. Don't be afraid to say if it sounds serious - my guess is that this one actually might be 

[5536paulj]

Can't hear a knock, but I can here an exhaust or manifold leak.

Use a piece of rubber pipe as a stethoscope, jam one end in your ear and move around the engine with the other end trying to find the noise, starting with the manifolds.

[Brynjaminjones]

Cheers Paul. There does seem to be some exhaust leak noise. I've tightened all the manifold bolts but will have another look.

The knock is probably most audible after 0:47 and after 1:58 in the video, but you can just about hear it throughout.

[IrishCJ6]

I can hear the knock, to me it sounds in time with engine therfore leading me to a rotating part?

What's the oil pressure like?

[Brynjaminjones]

That's my thought, although I'm going to take the belts off just to check. I doubt that'll make a difference though.
I'm also wondering about the flex plate.


Oil pressure is excellent when cold. Once at operating temperature, hot idle is around 10, jumping to 35-45 the moment I touch the throttle. The rev at the beginning of the video should show this.

[donk498]

Sounds like valve train to me. Take the rocker covers off and have a look.

[Brynjaminjones]

I'd much prefer if that was the case.
Several guys on IFSJA seem to think flex-plate. Does that seem feasible?

[bgbazz]

The knock sounds a lot like a rocker arm to me...that might be caused by a faulty lifter, but not always. I'd follow Donks advice and get the rocker covers off for a look...do them one at a time and you might get lucky with the first one.   

A piece of broom handle, or similar, about 2 ft long, pressed tight against your ear and the other end held against any suspect area will tell you heaps. I use a 20" screw driver the same way...the handle is more comfy on the ear.

[wildwood]

Agree ....rockers and then.....hydraulic lifters...
I am sure we mentioned this before, but with age they carbon up and can't get the full flow of oil in them so rattle or knock.... They also wear and adopt a curved surface....so they get stuck in one position and wear even faster.....
Easy to replace and about the size of last finger joint.....or smaller...

[Brynjaminjones]

Thanks guys.
Another symptom I should mention - the knock is only noticeably there when the engine has warmed up a little. My understanding was that a valve train problem would improve once the oil warms up and flows better, rather than the other way around?

[5536paulj]

I think everybody has made good suggestions, think you need to use the piece of rubber pipe or broom handle to find it as all of the above inc flex plate could cause it, as could use of a different oil and filter, although unlikely.

Let us know where it's coming from.   

[bgbazz]

 ....Just a quick thought for you Bryn...cold oil tends to be fairly thick, but as it warms up to operating temp, will thin out somewhat...one of the reasons that oil changes are normally done when the motor is at, or close to operating temp.

[Brynjaminjones]

Thanks again guys.

I was hoping that oil temp would help the diagnosis as I thought it was only making noise at operating temperature, but I think that might not be the case.

I've had a play tonight - I took the belts off and started it cold, to rule out any accessories. Doing that made it clear that it's definitely got quite some noise when cold.
Assuming this is the same noise, I'd say that tonight it sounded a bit more "tick" like - maybe a bit less heavy, and seemingly (I hope) from the top driver's side of the engine, so that goes with what you've all already said.

[dieselj20]

Thanks again guys.

I was hoping that oil temp would help the diagnosis as I thought it was only making noise at operating temperature, but I think that might not be the case.

I've had a play tonight - I took the belts off and started it cold, to rule out any accessories. Doing that made it clear that it's definitely got quite some noise when cold.
Assuming this is the same noise, I'd say that tonight it sounded a bit more "tick" like - maybe a bit less heavy, and seemingly (I hope) from the top driver's side of the engine, so that goes with what you've all already said.

sounds like lifter noise

[Dave69]

the lifter noise on mine is way worse than yours.

[Brynjaminjones]

That's reassuring Dave - I've also spoken to James at Peak Jeep who had the Waggy last week, and said he noticed it but wasn't concerned. I'm going to keep an eye on it and drive steady to see if it gets any worse.
We've made allowance for a rebuild when necessary.

[thorna]

Can't help on the knock but that looks a seriously sweet ride! Wood effect to boot! Good luck.

[IrishCJ6]

Oil pressure is your key, if you notice any difference, stop immediately as it will rapidly go down hill from there and cause more damage than needed.

[John McBride]

My old AMC 4.2 developed a knock like that also at idle and half of engine revs. Got worse when pointing down hill and stopped when pointing up hill. Drove me to distraction, pulled the rocker cover, sump, belts off etc. Checked crank end float but could not see anything out of spec. Oil pressure ok.
Then noticed that slowly over a few months the crank case was building more pressure.
Decided to pull the motor and found 1 piston had its top ring broken in several pieces. A compression check did not show this up initially but I'm sure if I had checked it later on, it would have been down on that cylinder. So to get to the point, monitor if you crank case pressure is increasing and maybe get a scope down the bores to have a nose around.

[Dave69]

i had blow by on the front two cylinders, the remaining three had good cylinder seal. replaced piston rings and deglazed the bores. was going to change lifters but the ones i sourced wouldn't fit so stripped and rebuilt the ones i had. downside was that one has a weak spring which allows the oil to drain quicker so the rod bounces.

new lifters to be sought and installed at some point, oil pressure running at 50 the 10psi at idle held in drive. over 10 psi when sitting in neutral. oil changed to 20w50 which reduced the tapping noise

[Bubba]

lifter