One way to find out is to get yourself a set of oil pressure readings using a mechanical gauge. cold idle, cold 2000rpm, hot idle, hot 2000rpm.

 

I had the same thing on my disco. Sounded smooth till it warmed up then I got this annoying tick. Most of the time it would be rhythmic but sometimes it was intermittent only pausing for a split second if that makes sense. I tried Marvel mystery oil and it went away for maybe 2 days worth of driving. Switched over to Rotella and it went away again....came back later that day . Listened to that annoying tick for 3 years till I ended up with a cyl 8 misfire that kept coming back after a coil and multiple plug/wire changes. That was the last straw so I opened up the engine. On another thread I mentioned that I found a bad pushrod, rocker assy and bent valves. I took out my cam and several lobes were worn down to nubs. 136k on this motor b.t.w For some reason the motor only ticked when it was warm with all of those bad parts. First I would pull the plugs and see if any of them are super clean (steamed clean). You can also get a cheap boroscope cam on amazon to see if any of the piston heads are the same. Check the oil and see if it's milky. If it all looks good I would look at the top end. Hope that helps a bit. Good luck.

 

 

Sounds like you have to not worry about it until something goes wrong that you can diagnose. Otherwise, you are chasing gremlins and completely overhauling for maybe no good reason, or a good reason.

 

In the meantime you could buy a used P38 Engine, and rebuild it on an engine stand for the day that it happens. Could be a fun project, or get a cheap 4.8 LS and rebuild that for a future swap. If you like the truck, and when it dies will have to buy another truck, that may or may not be a good truck, why not be proactive?

When I have a garage I may do just this. Get a 4.8, and tear it apart, rebuild it, and put it in mine or a different Disco II or Range Rover. Have a little fun.

 

I have the same issue with the ticking noise. I was told it was the lifters which land rover knows about on D2 and refuses to do a recall on them. It has something to do with the oil not circulating properly okn these engines which build up sludge. Best advice, which I'm doing now is use royal purple 10W40 (depends how's your climate in your area)

 

You had a liner that was slipping at 200 plus degrees, it's pretty common. Your lower thermostat did take care of the problem, you are lucky some of them start ticking at a hundred and fifty degrees

 

 

 

I have the ticking at idle too, but only when hot. And it is intermittent, I do not notice a clear correlation to the temp. It goes away when increasing the revs slightly (900..1000) or after driving a few hundred miles, but the next day it is back. Recently I switched to a 82C thermostat, but that makes no difference. Since the frequency of the knocking sound is clearly at 6.25Hz (= 375rpm = camshaft rotation rpm at idle) I assume it is something around the camshaft/lifters. Wouldn't a slipping liner tapping at 12.5Hz (=750rpm = idle)?

To get a feeling for the frequencies you can use this tool: