Engine knock

Here all the details

1991 4.0 engine in an XJ 187,000 miles owner took to mechanic, main bearings and oil pump replaced, noted on invoice that crank has scaring... wierd thing is this noise only happpens at start up or cold engine.


Thanks,
Todd

I've never owned an xj that didn't knock to some degree

Also make sure it's really knock and not just noisy injectors. I looked at a TJ last week that sounded like noisy injectors till we got underneath, then you could really hear a KNOCK from the oil pan area. We passed on it..

I am not sure if the problem described below belongs here, maybe.

My XJ (1984, 2.5 lt) is making a wierd noise near 3000 RPMs, when I let off the accelerator, sounds like there are several nuts banging together somewhere (like inside a can), or like a chain dragging on metal. You can hear it easily when cold, but you have to really listen for it when hot.

Any ideas? (I keep my fingers crossed!!! LoL)

Many thanks and regards
---------
John

could it be the flexplate bolts.

89xj said:

could it be the flexplate bolts.

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How do I check the flex plate bolts?

redwagon said:

How do I check the flex plate bolts?

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Jack up the vehicle and crawl underneath. Where the tranny bellhousing bolts to the engine, at the bottom is a light gauge metal inspection cover. Remove that.

With that out of the way, you can rotate the flywheel (flexplate) to expose the torque converter bolts one at a time. Check 'em with a torque wrench. If they are tight, use a pry bar and pry against the flex plate to look for cracks. When they crack, the crack is easy to see once you know what to look for (big help, right?). It's usually a semi-circular crack that forms around the outside of the reinforcing ring where the 6 bolts hold the flywheel to the crankshaft. To see a crack you will need a bright light. Check two or three times, rotating the flywheel between looks.

redwagon said:

Here all the details

1991 4.0 engine in an XJ 187,000 miles owner took to mechanic, main bearings and oil pump replaced, noted on invoice that crank has scaring... wierd thing is this noise only happpens at start up or cold engine.


Thanks,
Todd

Click to expand...

piston slap.

and they slapped in new bearings without machining the crank? are these people retarded?!?!?:shocked:

SV1CEC said:

I am not sure if the problem described below belongs here, maybe.

My XJ (1984, 2.5 lt) is making a wierd noise near 3000 RPMs, when I let off the accelerator, sounds like there are several nuts banging together somewhere (like inside a can), or like a chain dragging on metal. You can hear it easily when cold, but you have to really listen for it when hot.

Any ideas? (I keep my fingers crossed!!! LoL)

Many thanks and regards
---------
John

Click to expand...

While your down there looking at your flexplate, try to shake the catylitic converter, if the guts come loose they can also make a rattling noise.

Turtle said:

While your down there looking at your flexplate, try to shake the catylitic converter, if the guts come loose they can also make a rattling noise.

Click to expand...

I checked that out, I nearly had a heart attack some years ago, when my brand new (at that time) Civic made such a noise. It was from gravel caught between the converter and its shield!

No, it's not the cat. It sounds as if it coming from the front of the truck, not underneath. Maybe the cam shaft chain?

Thanks for your input though, sincerely appreciated.

Rgds
--------
John

SV1CEC said:

I checked that out, I nearly had a heart attack some years ago, when my brand new (at that time) Civic made such a noise. It was from gravel caught between the converter and its shield!

No, it's not the cat. It sounds as if it coming from the front of the truck, not underneath. Maybe the cam shaft chain?

Thanks for your input though, sincerely appreciated.

Rgds
--------
John

Click to expand...

check that the harmonic balance isnt "walking" into the timing chain cover.

on the hamonic balancer , would there be dents on the timing chain cover?

Going to check flexplates bolts first.

Then checking balancer

Started the XJ last night again loud clunking when first start up, then let it run about five mins.... then restart later , no noise , oil pressure is about 40-50 while running..

I'll post what I find out this weekend

Thanks to all.

Todd