Before you start looking at lifters, read my sticky and valve train noise so you know what to look for starting with the rocker shaft, arms, the hardened tip of the arms, the push rods then the lifters, one at a time both for wear on the hardened surface as well as the lobes of the cam.
Let us know what you see.

 

Just got through inspecting everything, the rocker shafts and arms looked good, but I'll give them a cleaning and another look to be safe, since they did have a bit of sludge on them. After reading more on cam wear in the RPI article, I'd agree with Savannah and say that the cam looks fine too, no brown stripes. I also looked at the lifters, and by my eye some show a tiny bit of wear, but I would guess that they are not too worn to reuse. There were a few stubborn ones but I was able to pull them all by hand.

Something that may be interesting, is that one of the lifters was not sliding freely before I removed it, and it happened to be in the area that I had best narrowed down to be where my tick was coming from. These are the lifters that had the most wear:






Would soaking the lifters in carb cleaner, or whatever is recommended to clean them be beneficial? I was thinking with the amount of sludge that is in the valley some may have made its way into my lifters causing one or two not to fill properly/stick. As far as cleaning the engine goes, I was thinking that I should soak/scrub the pieces that I can remove, such as the rocker assemblies and pushrods to give them a thorough cleaning, and let the Rotella do its work on the sludge in the block, so I don't go sending chunks of crap into my engine.

 

Might not hurt to clean them but make sure you put them back in their same location or you will have issues.

 

Everything's back together, and what do you know, it still ticks. At least it runs and has no codes haha. I do feel like the low end power and fuel economy are slightly better than before, but maybe it's just placebo. The one thing I didn't check was pushrod length, some were a bit worn on the end but there were none that were bent or otherwise damaged looking.

Another fun development though, is that I have a 15ma draw on my battery that kills it overnight. I've pulled all the fuses with the meter hooked up between the battery and negative terminal, and nothing changed the draw. The tach wire (I think, it's brown and yellow) on the alternator is a little twisted, so maybe that's shorting and causing the drain. I'll have to double check that.

 

Sorry to Jump in. I am new to this. I purchased a 99 disco 2 a couple of weeks ago. I have the same symptoms as ProRider. I tested the oil pressure as you have suggested. Cold Idle: 50 Cold at 2000 RPM's 55
Hot Idle: 20 Hot at 2000 RPM's: 40. I pulled the plug wires off one at a time while running. The tick was less noticeable when I removed #4 plug wire and stayed about the same when removing the others. The tick goes away at the higher RPM's or when the oil pressure hits about 30 PSI.

I thought I would pull the pan and check the bearing on #4 but thought I would get your opinions before proceeding.

 

One popular theory on a tick that comes on at warm engine and goes away at rpm is that the cylinder liner that is slipping can't reverse fast enough to keep up with the piston that is dragging it aong for the ride. But not normal oil PSI specific.

I would suspect bearings would be more of a knock. You can take a yard stick, hold one side to your ear, and touch along valve cover with the other end. Easy to hear what is going on under there, if it is valve train.

Would expect you'll get better results with good jumbo oil filter and Shell Rotella 15W40.

 

I puled the rocker assemblies today and did a complete disassembly and thorough cleaning (I didn't disassemble them before). I gave everything a nice coat of fresh oil and put it back together. The truck sounded great when I started it, no more tick. I drove it a couple of miles down the road to get it warmed up, and the tick was barely there but still a huge improvement. After a 20 mile drive the tick is back as bad as it was before.

I'm thinking if those $150 rocker assemblies turn out to be good, I may order those, and a set of pushrods since mine show a bit of wear. Does that sound like a reasonable next step?

 

Sounds like a plan. When you took things apart, did you clean out the oil ports in the rocker arms?

 

Yup, I sprayed cleaner through the pushrod cup of all of them to make sure it was coming out of the port inside the arm. Am I right in guessing that once the oil that I applied directly to the parts when I assembled them stopped cushioning things, the amount of oil that normally gets pumped up top wasn't sufficient for my worn parts and that's why the tick went away at first, then slowly came back?

 

Yep. So mechanical oil PSI test showed what? You running somethingW40 oil?