Disco II V8 stranded in Czech Republic - help!

Thanks for the explanation, that all makes perfect sense to me.

Hence, presumably, why engines built with "top hat" liners supposedly cure
the problem for once and all?

Examination of spark plugs this morning showed all same colour and no sign
of bleaching or washing, so dealer has now started to pull the top end
apart. While they do that, I will be quietly praying over the weekend to the
cylinder head gasket god (in case one exists) that it will turn out to be
nothing worse than a blown head gasket!!

More news early next week, so fingers crossed!

Simon


"Badger" <[email protected]> wrote in message
news:[email protected]...
>
> "Simon Oates" <[email protected]> wrote in message
> news:[email protected]...
>> Thanks for that. I guess that's probably what the dealer was trying to
>> say when I was asking about porous liners, but it got "lost in
>> translation"
>>
>> Simon
>
> Just in case you don't know, what actually happens is that the ally of the
> block cracks behind a liner (normally near the top and close to a head
> bolt hole), allowing the block to loosen its grip on the liner when hot.
> This can result in coolant being forced up the side of the liner, or
> combustion gasses being forced into the waterways.
> During the manufacturing process the liners are force-fitted into the
> block with the block heated to expand the ally. The liners would sometimes
> lift a few thou as the blocks cooled during manufacture, believed to be
> caused by non-uniform cooling of the block. The top faces were then
> machined flush as the top of the blocks were final-machined. The cracks
> form (normally accelerated by overheating) in the first place because of
> unequal wall thickness of ally around the liners, caused by shift in the
> sand cores as the molten ally is poured to cast the blocks.
> In service, if a block cracks and loosens its grip on a liner, the liner
> can then slip downwards a few thou, compromising the already poor seal
> across the head gasket. It's the combination of a crack, a slipped liner
> and an inadequate seal that causes the loss of coolant/overpressure.
> Badger.
>

"Simon Oates" <[email protected]> wrote in message
news:[email protected]...
> Thanks for the explanation, that all makes perfect sense to me.
>
> Hence, presumably, why engines built with "top hat" liners supposedly cure
> the problem for once and all?

Yes. They are firmly inserted all the way (and held there!) then the liner
tops skimmed.

> Examination of spark plugs this morning showed all same colour and no sign
> of bleaching or washing, so dealer has now started to pull the top end
> apart. While they do that, I will be quietly praying over the weekend to
> the cylinder head gasket god (in case one exists) that it will turn out to
> be nothing worse than a blown head gasket!!

Had a 4.6 engine from a hillrally motor in here some years back with blown
head gaskets - blown to the point of warping the heads by 8 thou (!!) and
losing chunks of gasket to the outside world next to 4 cylinders (centre two
on each bank, strangely enough). It was absolutely fine after new gaskets
and a skim of the heads, even though I suspected the worst re. cracking.

> More news early next week, so fingers crossed!

Will await your news, fingers crossed for you.

Badger.