If it's a ring issue with 30 psi, I'm willing to bet you'll find major cylinder scoring on number 5. The only disco I've torn down that had cylinder damage was due to lack of oil. These engines are almost at the point they don't make enough power to damage the rotating assembly unless they have help via a major oil or cooling failure.

Even at 250k our DD was within spec to hone and install new rings. It's pretty much everything that's wrapped around the engine is what causes the disco to be such a maintenance nightmare with age/neglect.

 

Thanks for the advice.

Pulled all the plugs, got 150-155 psi on cylinder 1,3,7
Wet tested cylinder 5, got 30 psi still, also holds that psi for a while. Maybe if I were more generous w the oil it would be different?

Does that Engine Restore do any good? There was a thread on here where someone used it to fix their cylinder 5 misfire. Clearly a temporary fix, but might we worth doing?

Plugs 7 and 8, below have some dark residue on them, the other plugs look great.
Photos below are cylinder 5, does not look steam cleaned, I suppose that only means coolant is not getting into the cylinder. I suppose a blown head gasket could still be on the exhaust side? Is that just a massive carbon build up on the piston? I generally run premium fuel for what that is worth. I did not pull photos, but it looks like the cylinder walls were evenly hatch marked. I could not see any unusual scoring.

Any thoughts on next steps? Pull the heads and see what I have? It currently runs, albeit poorly, if it is more than the heads, I think I need to get it to another shop, if it is the rings or other cylinder issue. Which raises the question of do I source another engine? We just replaced the rear frame and everything works, so I am all in on this truck. To a reasonable limit. I just bought a new Range Rover, which is pretty nice, I still love the Disco.

Is it worth tracking down a leak down tester? If it appears to hold the 30 psi?
I have tracked down a few machine shops to see who would be willing to take a run at these. I imagine it only makes sense to do all the valves? Should I bother with the passenger side, or just do the drivers side? Any repair kit seems to include both sides anyway. Or, it could always be something worse. From the above comments it looks like it is the head gasket. I have been waiting for this. 10yrs+ of discos and never had the head gasket job to do.

 

Time to pull the head. I'd go ahead and do both. Just had a small shop machine both my heads for 160 including refacing and sewing valves. That's price for the set.

Adding oil will boost the numbers if it's a ring issue.






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Hopefully that is all, does not look like too much of an issue. I have been calling around for machine shops, seems like most of them are out of business. Or the phone does not work. If anyone has a recommendation in Central NJ, or Philly, let me know.

If it runs quietly, do I need to replace the rods or tappets or rockers?

Any other things I should test before I start pulling it apart? I expect that once I get the head off and I can test it for leaks by pour gas into the combustion chamber. I am inclined to get them both professionally cleaned and tested, but not having luck finding a shop.

 

Wouldn't hurt to look at the cam to see if any bearings have been walking or lobes worn. You'll likely not be able to remove all the lifters easily as they mushroom on the cam side making it difficult to pull upwards sometimes. Sometimes they are so bad you have to drop them down once the cam is out. That requires the engine being pulled from the vehicle.

That being said, if everything looks ok id slap it back together and not worry about it.

 

There is no water jacket passage between the head and block for the middle 2 cylinders on each bank, see photo below. It could be the exhaust side. You would probably be able to feel it if that was the case and you held your hand down there while running. But the blow could very well be between the cylinder and valley, see other picture.

 

I will also say pull the head, but before doing that, get the valve cover off and make sure nothing looks weird with the rocker/valve spring that could be holding the valve open or something. 50% chance you have some issue with the valve seat since the wet test did not increase the compression, like maybe something went through the engine and nicked it or the seat dropped out.

 

Thats a good idea, ill take some photos.

 

What am I looking for on the rockers? It looks fine to me, but I would hate to get it all back together. I suppose I need to get the rocker pulled off to get a better look.

I ordered a new set of fuel injectors, these are in pretty bad shape, is it better to install ones from china, or try to refurbish mine knowing they did not have a problem before?

Interesting trick for draining the coolant. With the inline thermostat. Put a jug on the top hose that comes out of the engine block and blow into the upper radiator hose, the one that goes into the top corner of the radiator. That will push about a gallon of coolant out of the system with out spilling it all over the place.

 

With the plugs out spin the engine over by hand. Follow the travel of the rocker arms on your weak cylinder. Compare the length of travel to that of your good cylinders.

My 03 head had good travel but crap compression due to carbon buildup. Likely a combination of multiple short travel intervals and 87 octane fuel. Had less than 85k on the odometer