All good points.

Definitely not an exhaust leak. New gaskets (head to manifold and manifold to down pipes) on both sides. Did this after chasing what sounded like a "diesel" noise that came from the passenger side for quite some time. Turned out to be a leak in the weld at the down pipe flange that finally let loose on a drive home from Tahoe - sounded like open headers on just one side. I removed the catalytic "Y" assembly and had the flange re-welded at a local muffler shop for $10.

I did change to a 180 degree T-stat - it was a Motorad unit from AB. Maybe I'll try a genuine grey one from Lucky 8.

With all the recent work, I stopped short of replacing the rocker assemblies. I ordered some refurbished ones from a used parts supplier, but they looked worse then mine w 190K - they were clean (the new ones), but the shafts were scored. There was no sludge build up at all around the rocker shafts, timing gear, or pan - it all looked surprisingly clean. I know this doesn't mean there may not have been sludge built up within the shafts. Also, would sludge clogs in the shaft assemblies only cause the ticking when up to operating temp and at low RPMs (< 1,200)?

For now, I'll just enjoy the tick free running as long as I can; its been quiet and smooth for about a week and a half now (but something tells me it'll be back soon)...

 

I'll try a genuine grey t-stat
new rocker shafts can be had for $50
what you need to check on the rockera is they are aluminum, but the push rods are steel, so they press a steel cap into each rocker to keep it from wearing, these caps can come loose and cause top end ticking

 

Thanks.

Already ordered the genuine 180 t-stat.

I'll check for the steel caps on the rocker arms. If one (or more) were loose, could they re-seat themselves and loosen back up intermitantly - causing the noise to come and go?

It seems to me that loose rocker arm caps would be more of an issue (ticking noise) when cold - or do the dissimilar metals expanding at different rates have something to do with it?

 

as soon as you pull the rockers off and look at it, your first words will be "who thought of this"

 

mine has a low rpm rattel dont discount the cat heatsheild mine is cracked and rattels

 

So after almost two weeks of tick free, quiet operation, the noise started to come back a couple of days ago. Much lighter than before and infrequently, but it was definitely back. I installed the genuine 180 t-stat yesterday, and it seems to have made a world of difference on how she runs. MUCH smoother and quieter - no ticking. I cannot empirically state that the 180 degree genuine t-stat works better than the Motorad 180 degree unit, but it sure looks that way. I'll continue to monitor and post.

 

Today I installed a new power steering pump, fan clutch, and genuine 180 t-stat (replacing the motorad one which was losing its internal seal). Tick is still there. Kinda pissed, looks like the rockers are next.

 

The ticking is back - and worse than ever...

My initial impression of the genuine t-stat probably had more to do with my head than with how she was running. Again, the ticking was there, but it did not seem to be as bad - kinda like when you think your car is running smoother after an oil change...

I decided to just deal with the noise and do some of the major service items this past week end. Differential and transfer case oil, tranny fluid and power steering fluid. Did not drive the Disco until yesterday morning. Ran fine, the clunk in reverse was much better, smooth shifts, steering felt good. Then, on the drive home, it let loose. The ticking increased in volume and frequency - real bad.

I now suspect the power steering pump may have been the culprit all along. Changing the diff and transfer case oil would have had nothing to do with the cacophony. The tranny felt fine the whole time. But the noise coming from under the hood sure did get worse. Power steering fluid (Lucas PS Fluid w Conditioner) seems to have really pissed it off. I'm going to run it until it gets super noisy again, shut it off, remove the accessory drive belt and see what happens. No noise = bad power steering pump... We'll see.

 

Man, that's awful. You would think with the outrageous cost of these trucks and their parts, they would be at least somewhat strong. Not the case though unfortunately. Good luck on the repair. I hope this ends your annoying tick. Mine was a cam bearing that fell out of the block and was rattling around on the cam. I had checked about everything before I finally found it. I even tried putting an oil additive in to see if it helped. Of course it didn't, never does! It just got so annoying, I guess I was willing to try anything. LOL!!!

 

Well?