RR 4.6 overheating

Hi,
I have read several comments about over heating, but as ever, nothing fits my problem:
First the background:
The car is a 2000 4.6 HSE & has a quality LPG fitted in 2008.
[I now know all the negatives about LPG]
A month back the heater hit the red and it was found that the thermostat was faulty.
Both heads were taken off, skimmed and re-built with the correct gaskets etc., to a high standard.
The car worked ok for a couple of days then overheated when on LPG.
After lots of checking, it was decided it was a porous lock.
Iron Tite was used to the exact instructions.
The car worked ok for a day on both petrol and LPG, then started to overheat again.
The LPG is now totally isolated from the engine including the water cooling pipes. The engine is just that, an engine.
It now also overheats on petrol.
We have a new thermostat - it still overheats.
Did a pressure test on the cooling system which is ok.
Done a compression test with all cylinders coming out at the same reading and all very good.
When it over heats, the hot water comes out of the expansion tank like a fountain.
The expansion tank cap was replaced.
The other weird thing is that when the engine is switched off, it can return to normal temperature in less than 5 minutes.
A vacuum test has been done to remove air locks.
The water pump was removed and found to be working ok [metal fan blade]
Now we are at a dead end.
Any thoughts greatfully received.
Thanks

Blocked Radiator?? Viscous Fan not working ??

engine is fooked iron tite does not work for long if the crack in your block is growing with the overheating mine did the same thing but i got a few months out of it but the end of the day your going to need a engine ..

Slipped Liner??

i had the exact same issue,, not with l.p.g fitted though,, it was a new engine in the end as we couldnt rectify the problem no matter what,, i fitted a coscast lump in the end,, superb,,

Hi Guys,
Thanks for the replies.
Yes, we even fitted a new Viscous Fan and still no luck.
It looks like it's doomed.

Did you check the tstat if it is opening properly?put in in a kettle with water and look if it is opening when the water starts to boil,i bought two tstats to replace mine and both of them were faulty so the third was fine.check also if the coolant is coming back to the exp tank from the bleed pipe.chek for cold spots on the radiator also,if the above doesn't solve it,prepare yourself for a new block.good luck

:behindsofa:
Been there, done that....Twice, once with my old 3.9 Classic and the second time with my 4.6. Remove the plugs and look for one that appears "Washed" clean, that will confirm the faulty cylinder(s).
Put a new short engine in it and you can start again with a clean sheet. Replace the rad. whilst you are at it.
Both of mine ran on Petrol not LPG. I am of the firm belief that LPG greatly increases the chances of block related problems though which can dispel the feeling that money is being saved especially after having to fork out around £3000 for a new short lump.

Hi,
Thanks again for all the replies.
Everything asked has been checked and is ok.
Compression test comes back spot on.
Pressure test on colling system is good.
Sniff test on cooling system is ok.
Radiator seems ok.
Despite all that everything points to a new block.
Has anyone got any recommendations as to a good suppier?
Thanks again.

HHMan said:

Hi,
Radiator seems ok.
Has anyone got any recommendations as to a good suppier?
Thanks again.

Click to expand...

Rads are the most likely cause with these engines, there's an advertiser in LRO who re-manufacture blocks which apparently cure the slipped liner issue once and for all. Turner Engineering - Remanufacturer of Land Rover Engines and supplier of Land Rover engine parts

Forgot to say £1250 + drat! You pays yer money I suppose...