First time poster, long time browser....what a wealth of info is here, hopefully someone can lend a hand on this. I've done a head gasket on my old RRC, but nothing as adventurous as a full engine rebuild.

Bought a non running 03 Disco for basically nothing with the former owner saying his mechanic said that a couple of the cyliners weren't firing. Thought of replacing the engine, fixing slipped liners at worst, maybe just head gasket?

Finally got the whole engine out and found that one piston head looks to be bent!??! I guess that would explain the convex valley gasket I found on the way in and the corrosion in the cyliner, but is that also responsible for the gunk all the way up in the plenum and throughout the coolant lines? The liners seem to all be in place so is simply replacing the piston my next step? Are there any issues I should take into account even with the liners seemingly in place?

Thanks for any insight.

 

Wow....that's interesting. How does the liner look on the cylinder? Is it scratched up or is it still usable?

I'd be interested in seeing what the rod and wrist pin look like on that one. It could explain the damage.

As far as stuff in the plenum.....I can't imagine that thing was pretty while running, so it certainly could explain it. And as far as mixing oil and coolant, what does the head gasket look like?

I'd definitely want to get the block stripped and pressure tested before using it. And if you're going through all that trouble, you may as well get the shop to put in top hat liners so you won't have to worry about it again.

Edit: Can you post a pic of the head from that side? I'm wondering if it dropped a valve and that would explain the mechanical damage. If so, that could also explain things in the intake and plenum.

 

Here is the head on that side, nothing too out of the ordinary...I think.

As for the cylinder liner, not too badly scratched, some rust but nothing that seems to bad that couldn't be cleaned up. And the head gasket seems almost new (final pic).

The damage, upon closer inspection, seems to be eroded away. No real break but almost as if it has been sanded or ground down.

??

 

My 2 cents is you got a hot spot that started pre-ignition in that cylinder. It started as a tiny fissure in the edge of the piston and he kept driving it until you got the nice blow out on the piston. It happens over time. Bet he ran cheap gas in it. I've seen heads blown out just like that when someone pops a head gasket on the outside but keeps driving it with the blown gasket. It eats the metal out of the head just like that.

 

Also notice the location in relation to the water jacket. I wonder if he ran it dry of coolant and it got really hot there where it's thin, that could of been where the pre-ignition started. Could of cracked the piston and then he fixed whatever was causing the water loss, but the damage was already done. Just took time to burn out the piston from that point.

 

After seeing those pictures, I have to agree with photocrimes. That would seem to be the most likely cause. Zooming in on your original it seems to be more melting and less physical damage than I originally thought (didn't zoom in at first).

Definitely have those heads gone through and the block pressure checked. If it was overheated, you have a very good chance of cracks. See if the machine shop can heat the block while the do the test. It's the only way to know for sure.....if the crack is behind the liner and the liner is tight until the block warms up (typical of loose but not slipping liners) you won't know otherwise.

Of course if you top hat them it should all be good even with small cracks behind the liners. I'd like to beat the Land Rover engineer who thought tapered liners were a good idea.

 

After seeing those pictures, I have to agree with photocrimes. That would seem to be the most likely cause. Zooming in on your original it seems to be more melting and less physical damage than I originally thought (didn't zoom in at first).

Definitely have those heads gone through and the block pressure checked. If it was overheated, you have a very good chance of cracks. See if the machine shop can heat the block while the do the test. It's the only way to know for sure.....if the crack is behind the liner and the liner is tight until the block warms up (typical of loose but not slipping liners) you won't know otherwise.

Of course if you top hat them it should all be good even with small cracks behind the liners. I'd like to beat the Land Rover engineer who thought tapered liners were a good idea.

 

Pistons look steam cleaned, meaning you are getting coolant in the cylinder. Excessive pressure in the crank case would blow the valley gasket out.
What do you mean with piston head? You mean the top of the piston or the cylinder head?

 

Ah I see part of the piston is melted away, missed that in the first look. That is some serious damage.

 

I'd say blown head gasket leaking coolant into #7 cylinder (that's why it is cleaned of carbon) The leak eventually got bad enough that a volume of coolant greater than the capacity of the combustion chamber leaked in (probably while sitting unused) and the next time he turned it over the hydraulic pressure busted the piston. It had to go somewhere. He continued to drive the vehicle after that with the broken piston and so the area of the break eventually became eroded as we see it now.