Did you ever check oil pressure with a gauge? You also need rocker shaft assys. Also, do a search in the forum for "Walked Cam Bearing".

 

I bought this bad boy not running. $300 CAD for a 2004 Disco 7 seater with 150000KMs was too hard to pass on, and that was originally as a parts car, but I’ve decided to sell my ‘99 and fix this one up.

I did run the engine, which sounded like a freight train given that not only was there an exterior head gasket leak in two cylinders, but the owner had cut out both cats!

Honestly the rocker assembly looks
fine save for some oil clogging here and there. All rockers move smoothly, though there is some sludgy resistance.

I’m not at all afraid to tear into this engine, I’ve done extensive engine work on my BMW 850i and 540i, so I’m ready I also have a 1999 Range Rover Autobiography that I just bought that will need some work, so this will be the pilot 4.6 project.

what I don’t want is just to replace things for the sake of it, and I’m interested to get to the bottom of this particular failure. What I do know for sure is this:

1-the head gasket is blown on the on the passenger side, badly in two cylinders to the outside.

2-when I removed the valve covers both valves in cylinder 6 were not returning fully to their closed position. There was enough play that the rods would knock around in the rocker cups, but not enough that the rods could slip out. This rocker cups were well pounded by the rod tips. The lifter caps were also pounded down about a quarter inch from the upper edge. The rods showed only minor abrasions from pounding the rocker cups.

3-the retaining clip on one lifter from both cylinder 3 and 4 broke, and the push rods pushed the caps aside and were pushing deep into the lifter. The two push rods showed minor damage to the bottom ends.

4-the bottom surfaces of two lifters shows a square patterned wear mark. One lifter was the one from cylinder 3 that had a broken clip, but the other was from cylinder 1 and showed no damage or wear anywhere else back up to the rocker.

5-the rocker assemblies have some friction due to sludge, but still smooth. It looks
like besides the two damaged rockers that it would function smoothly with a good clean. The two damaged rockers still rotate on the rocker bar. Also, when I removed the rocker bar the valves from cylinder 6 that wouldn’t reseat, returns to their closed position. When I removed the head, there doesn’t appear to be any damage in any cylinder.

6-the cam looks fine, but I’ll obviously know more when I take it out.

Next job job is to take apart the heads and look at the valves and guides.

i agree that oil starvation seems likely, but it almost looks like someone but random pieces back into this engine.

 

I cleaned my rockers with extra strength oven cleaner and a scotch brite pad, and made sure passages were clean and clear. I have 2 D2's and one for parts. There is no 12 step program for this addiction.

 

So here’s an update:

I removed all of the valves and everything looked great. The valves actually look pretty good and all slid nicely out except one.

the intake valve from cylinder 4 needed to be coaxed out. It must have been a bit bent or warped at the top because it would not slide nicely into any other intake guide. All of the other intake valves slid nicely into its previous guide. That valve was one that lines up with a lifter that had a broken clip at the top, and no damage to the bottom surface.

so an intake valve is needed along with a handful of other stuff, but it all seems so disjointed, and the cam doesn’t seem damaged at all from what I can see and feel. The heads need decking for sure, but everything looks normal, and while I will clean up the valves, the stems all look really good, and there is only moderate carbon on the exhaust, and virtually none on the intake ones.

next up is disassembling the rocker shafts...

 

I took the rocker assembly apart and everything looks fine except the two damaged rockers.

after some thought I think I have narrowed down the issues.

1- the head gasket blown is a separate issue.

2- the issue has nothing to do with the rocker assembly or the valves.

3- the issue is with the 4 broken lifters.

after looking at the head and rocker assembly, I think I was mistaken about the stuck valves in cylinder 6. Instead what happened was the two lifter for those two valves were compressed. The caps for those two lifters sits halfway down the lifter for some reason. This meant that when the cam
lobe pushed the lifter up it pushed the push rods up, but only enough to smack the rocker cup, not move the valves. This is why the rods rattled the whole time I hand cranked the engine. I thought the valves were stuck, but it was actually because the lifters weren’t lifting the push rod high enough to do anything but make light contact with the rocker cups.

with the engine running the valves in cylinder 6 would likely not be opening at all!

the other two damage areas were the intake lifters for both cylinders 3 and 4. The retaining clips had broken on both and the caps had flipped vertically. This left the pushrods to move up and down inside the lifter as the camshaft lobes brought them up and down. There was no damage to the rockers, and no rattling of the rods that I noticed, but I could have missed it.

it looks like neither intake valves for cylinders 3 and 4 would have opened during operation either.

the last bit of damage were the two intake lifters from cylinders 1 and 3. Both had some scoring on the bottom faces that contact the cam shaft, in a square pattern. The camshaft shows no noticeable toughness or damage to either of those lobes, or from any other lobes for that matter.

All of the lifter bores allow a ‘good’ lifter smooth access, though some of the older looking lifters seem to have mushroomed slightly.

what would have cause the top clips of two lifters to break?

and what would cause to lifter caps in the same cylinder to drop to the halfway mark?

 

If I remember correctly, lube if fed to the lifters from the lifter bores, to the rocker shafts from the cylinder head through the rocker stanchions at the front of the head. Is the engine sludged up? Sludge is known to foul the oil feed holes in the rocker stanchions. Sludge could foul some of the lifter feed holes also - its feasible. Check the rocker shafts and make sure they are not upside down where the oil feed holes are at the top of the rockers instead of the bottom.

It almost does sound like someone swapped in some bad parts. Oil pump failures will make all the lifters bad, not just a couple.

 

"...the other two damage areas were the intake lifters for both cylinders 3 and 4. The retaining clips had broken on both and the caps had flipped vertically. This left the pushrods to move up and down inside the lifter as the camshaft lobes brought them up and down. There was no damage to the rockers, and no rattling of the rods that I noticed, but I could have missed it."

My first thought is someone removed and disassembled these lifters to "fix" them, put the cup in upside down, then couldn't get the snap ring back on so left it off.
At some point you have to stop. I would leave rotating alone, hook up a good aftermarket mechanical gauge to the location in the front cover, Reassemble and run it. Take it from there. You are still money ahead.

 

There were two rocker cup holes that were blocked where they connect to the push rods, but other than that there wasn’t much sludge.

the oil is dirty and I will make sure to clean everything before reassembling. The heads are being sent out for decking and cleaning/pressure testing, and I have some new parts coming to replace the damaged ones.

Im going to put it all back together and see how she runs. If I need to go back in and replace the camshaft so be it, it’s not that difficult to tear this engine down, and the head gaskets were the big fix here that won’t beed doing again.

if I could see it feel any damage to the camshaft I would replace it, but it just doesn’t seem damaged, and oil is flowing onto it.

what do you mean by a mechanical gauge? Where does it attach and for what purpose?

thanks for all of the input so far folks, I really appreciate it.

 

A mechanical gauge has a small oil line (copper or plastic) from the sending unit to the gauge, instead of a sending unit that uses a wire and electrical current to the gauge.. I got mine from Summit, Jegs might be better for your location. Just their cheap name brand is fine, if it gets good user reviews.