2000 XJ 166,000 miles
For reference the 0331 head was cracked and repaired by PO within the last year / 5000 miles (including head bolts, valve cover gaskets, camshaft, lifters, thermostat, timing chains, gears, timing gasket, cooling fan motor, and hoses). I have receipts from mechanic that did the work (I know and trust him) so I would think we rule out timing chain or lifters?

So it just started getting pretty cold and this has become noticeable. When I start up cold the XJ sounds like a good running diesel truck (can be heard from outside or while driving). After it warms up to running temp the diesel sound is gone (or at least reduced to the point where you can only hear faintly it if you crawl underneath).

At the risk of starting another oil thread here is what I tried. I switched from the 5w30 dino and unknown oil filter to Mobil 1 Synthetic High Mileage 10w40 and Bosch filter thinking the thicker oil might calm it down. The sound is still there.

Here is cold start up (with new oil):

And here is 10 minutes later after engine is warmed up from a short drive:

Is this something I should worry about? My other idea was to try Penn 0w30 oil thinking it might get circulated quicker but from what I have read if it is piston slap the oil isnt the issue but the temp of the pistons is?

Side question - Is synthetic 10w40 too thick for cold winter or is it ok if I give her a little extra warmup time? Should I change now or wait 3000 miles? I only put it in to test theory but I would hate to waste $50.00 worth of oil unless I have to.

Temp and oil pressure at time of warmed up video -

 

Is it very loud or just noticeable like a loud lifter click?

 

Its very clear in the videos if you play them. Pretty loud when cold, mostly gone when warm.

 

It sounds low end to me ..

 

Mine makes the exact same noise...

 

One of the mechanics where I work has an XJ with 300,000 plus miles and he said the same thing. I have read until my eyes bleed and only thing I can come up with is piston slap and its common dont worry but I just want to be sure....

 

Yeah you should be fine, my old zj with 250,000 miles did the same haha

 

Anyone else have this??

 

Almost sounds like it's coming from the top end to me......but difficult to tell for sure. If it is from the top end (valve train), u could remove the valve cover after the motor has fully warmed up and check to see that each rocker arm has oil pooled in it. If u see a rocker(s) with little/no oil pooled, u could have a plugged lifter(s) or plugged push rod(s).

 

If you had the 0331 head crack, then chances are your bearings are making that noise. I would drop the pan and replace them.

 

That is not what piston slap sounds like. Piston slap is a hollow sound that increases with light acceleration and goes away very quickly before motor warms up.
Yours sounds like valve train noise.

 

Get your hands on one of these from your friendly neighborhood parts store and listen to where the sound is coming from. An invaluable tool for all kinds of motorized diagnostic procedures.

 

Mine sounded the same when I bought it... except it never went away after it warmed up. It ended up being the bearings.

 

that's exactly what I feel like his problem is.. I agree with the stethoscope

 

Mine does the same thing and has been since I bought it in march. I have gotten all different kinds of opinions but no one knows for sure. When it is warm and driving it purrs. I have a rebuilt I will be putting in this winter and I will most likely have this one rebuilt so I will find out exactly what it is then.