interesting overheating scenario

[Romulus]

Yesterday I drove my Disco down the freeway on LPG, aircon on, no probs at all, purring along quite happily.
We then stopped, turned engine and went about our business. Suddenly, after about 5 minutes, it overheated with engine off, water steaming & forcing out of the top of the header tank lid, nearly lost half the water and took about 10 minutes to calm down so that I could remove the header tank lid and fill it up again with water.
Any ideas??????
On the way back I ran it on petrol with aircon, no probs at all when we got home. Could it be LPG related, as they do tend to run a bit hotter?:confused::confused::confused:

[Scouse]

It would have overheated because the coolant wasn't being circulated by the water pump & being no airflow through the radiator.
Some cars actually activate the thermo fans do stop this but I'm not sure if the Disco is supposed to do this.

Your explanation of why it might do this on LPG sounds feasible but I'm not up on LPG.

[Romulus]

so is this a design fault??....by the sounds of it it could happen on a regular basis?
I did hear the fans running, but I think they started after it overheated and by then it was to late

[PhilipA]

That is why radiators have pressure caps.
I remember I was in the parts department of Nissan in Riyadh getting a new exhaust for my 150Y that my son had broken in half during a driving lesson.

Looked outside and the car was spilling its guts, so I added "and a radiator cap". Fixed it.
Regards Philip A

[Romulus]

not that easy on a Disco 1 radiator....since it does not have any provision for a radiator cap on the radiator itself........

[Scouse]

Nice comeback but Mr A knows his stuff :cool:.

[PhilipA]

But the reservoir has a pressure cap.
This is the only place water can come out unless of course you have bigger problems like a cracked reservoir.
Regards Philip A

[Romulus]

But the reservoir has a pressure cap.
This is the only place water can come out unless of course you have bigger problems like a cracked reservoir.
Regards Philip A

yes indeed it does and thats where the steam/water is spewing out of.
What I still cannot quite understand is why it does that...it runs happily in the hot weather, then WHAM, coolant everywhere.
Could there be another problem on my Disco?, the header tank is OK, thanks for your advise.

[PhilipA]

The pressure cap is mainly to stop boiling after the engine has stopped and the temperature rises in the engine bay from "heat soak" which includes heat from the exhaust etc etc.
The coolant if at the correct ratio of 50;50 to water wil raise the boiling point of water to about 116C AFAIR.
The pressure cap at say 15lbs wiill add another 10c or so to the boiling point.
When water boils the steam has many times the volume of water. It is boiling in the block/heads and forcing the water out the cap.
You should consider a new cap and new coolant at 50:50 ratio to water not the crap you buy already mixed.
Regards Philip A

[Romulus]

great, thank you.
I have already replaced the coolant with a 50/50 solution, so I will get a new cap and that will hopefully stop the overheating/boiling problem.
Again, thank you very much!