Hey guys ive had a look around the posts but cant find the answer im after, its an EF xr6 on LPG. the car was loosing coolant slowly at first but in the last few weeks its seems to lose about 1-2LT within a day, i replaced the coolant about 3-4 months ago, then replaced the cap in case it was not sealing properly, no good so i replaced the thermostat just monday with an 88C one but still no good, but heres the twist when the low coolant light comes on the dash, i loosen the cap to relieve the pressure to top up the tank and the coolant will mostly flow back into the tank from the radiator. So the way its suppose to work is as the temp rises the pressure increases in the system which causes expansion of the coolant, so why then does the coolant disappear when hot and under pressure but when i remove the cap the pressure drops and the coolant retrieves back to the tank. Some ideas would be great. No apparent leaks either, but remember the system holds pressure so a leak is really out of the question. if it was leaking into the the cylinders at the rate of loss the motor would probably hydaulic lock. just trying to answer the obvious replies first.

Cheers Joel

check the lpg converter,the coolant may be going into the motor.

converter only 6 months old, doubt it is that.

Fine and dandy but how does it run on LPG. If its a little rough then your diaphram in the converter would be cactus.
Hows your interior smell? Like a rotten houso house? Could be your heater box leaking behind the dash.
Other causes I can think of would be a leaking heater tap, possible welsch plug, rad hose, or the dreaded head gasket.

Geez you guys are so negative! , maybe some poor slob is siphoning his radiator water cause he can't afford his own! (just got the water rates in - ) - watch out I might be heading your way next!

runs fine on both petrol and gas. No external leaks, question is why does the coolant reappear when pressure released. im at a loss to where the coolant dissapears too,the interior doesnt smell so im tipping that the heater core is sweet. some days it wont use a drop and other days pumps it out, im thinking its getting pumped out the overflow, system over pressurizes.

Sounds to me like it has an air pocket somwhere that is compresing as the pressure rises.

Was the heater turned on and the cooling system bled properly after the coolant change??

Found it, its the head gasket but it wasnt obvious as it was leaking right under the zorst, so it was drying as soon as it came out so i couldnt find the drips, it would pump out when on deceleration of the throttle only tho which was a bit weird . But i have since bought a new tickford motor and have just about finished stripping ready for a makeover. its gunna be mint.