This can be true of any engine. Thousands of small explosions/minute and lots of thing spinning at high speeds means all sorts of small noises can appear.

That being said, my 02 D2 has a loud exhaust leak when cold, but once it warms up it’s extremely quiet and smooth. It was a single owner with good maintenance and major engine work. But still. Easily as quiet and smooth as my wife’s Acura RDC (J35 v6) or my 4.4L Jag L322.

 

how low for oil PSI (warm engine @ idle) is TOO low? I'm having the same issue. runs good. but when it warms up to temp at idle tick-tick-tick. seems to do this on warmer days - 80's+

after a short run uptown today (4 miles) and back. truck was at temp (scanguage showing 194 coolant temp). I have the inline thermostat with a 180 deg unit in it. Fan clutch appears
to be working. Has resistance to spin when cold. A/C fan is working.

 

Try thicker oil?

 

rotella T4 15/40W. don't think that's the problem....using a stethoscope, the ticking is most prominent on the valve cover on the passenger side. 1st 2 cylinders from front of
engine.

 

Maybe try now with the valve cover removed. Listen to rocker shaft supports. Could be the notorious rocker arm defect. Mine was surprisingly loud for such a small gap.

 

if it is getting insufficient oil flow at idle, that would suggest plugged or restricted oil gallys or low oil pressure....no?

 

Or oil pressure relief plunger is stuck open. Does the oil pressure light ever activate? Do you think there is insufficient oil flow? Has the oil pump ever been inspected or replaced?

 

nope. only see it when ignition key is turned to on before cranking. when I first got the truck in 2022 (69K on it). I did a full fluid change and tested the oil pressure
at the plug in the front cover next to the oil filter housing (ie: no oil cooler). was getting 12 PSI at hot idle and 42 @ 2500 rpm. Have not checked since. I'll be
heading north next week and will bring the tool back down to re-test things when I arrive late oct.

 

Typically it is not a particular pressure, it is a symptom of a volume issue. Low oil pressure is usually associated with one of three things:
1. Walked cam bearing - allowing lots of oil to spill out of the cam bearing area and none reaches the rockers. Oil pressure under 10 psi
2. Cracked oil pump gears - diminishes oil pump output and reduced oil output to rockers (farthest away). Oil pressure under 10 psi
3. Worn rod bearings - similar to walked cam bearing.

I have had two of the three across 26 trucks, never seen #3 but it is possible. Checking oil pressure is just a way to rule out those issues. Thicker oil will not fix any of those

194 is too hot. Hot when idling is lack of airflow usually due to fan clutch, hot when driving is usually lack of coolant flow due to plugged radiator, hot in both is bad thermostat. Removing the thermostat element is always a good test to eliminate that as a cause. A properly functioning cooling system on a D2 will not get over 140 in cool weather without a thermostat and 180 in hot weather.

 

my 03 is in the VIN range for pooched front cover/oil pump...I'll be inspecting both in the fall when I come back to lower trumpistan.

Just took the disco for a run to get it up to temp (cooler today - 18 deg C). Truck was running when at temp @ around 172-174. Took
the front grill off with engine running. A/C was on. Noticed no cooling fan running (electric one). I cycled the A/C off/on to see if it would
engage and it did not. The fan Is not seized (ie: I can spin the blade).

I tested the main fan when idling after engine up to temp....using a newspaper put it slowly into the path and it would have chewed
it to pieces...not slowing any ..so it would be working ie: locking up.

Does this fan only come on if the outside temp reaches a threshold temp perhaps? [edit: looks like it kicks in when the outside temp
is > 75 deg F....and it was only 64...so that explains that.]

Truck was quiet as a church mouse idling (the way it should)...no valve tick-tick-tick....so this problem is definitely heat related.