i am currently working on a EF on gas, i put a low k's 4.0l in it a few weeks ago along with a reco radiator, all new hoses, new thermostat, heater tap coolant reservor and radiator cap, the problem was the gas converter frezzing and the radiator cap is spitting coolant/steam and the system wont hold coolant enough to keep the low coolant light off. a quick fix i have removed the thermostat so he can get to work untill i find what the problem is, this is where i am lost the car is running fine without the thermostat (tried other thermostats) the only thing that springs to mind is the heater hose off the gas runs higher than the rest of the cooling system, i know water/coolant will boil at 100 degree's C if air is present, so i am thinking that maybe the hose being higher has a air lock allowing the coolant to boil and spit/steam out of the cap, and running no thermostat the coolant doesnt get to boiling point, sound right any idea's ??

ok
have u tried a new rad cap?
also remove the small wobble thingo in the thermostat to allow small coolant flow

and is the water pump new?

the coolant hose to the gas convertor could be blocked by the opening of the thermostat ( i am presuming the hose to the converter comes fromt eh lower half of the thermostat housing )

yer tried diffrent caps and the water pump is in good condition, this only happens when its first started for the day and after about 5 minutes of driving so the thermostat wouldnt be open at the time it all happens. i was thinking of drilling a few 1/8th holes in the thermostat but i shouldnt have too, there has to be a cause for this. another bit of the story in december the car was running fine not a problem then he blew a heater hose and replaced it himself while he was there he changed his heater tap thats where the problems started, he had the spitting from the cap and frezzing converter and low coolant light anyways he had only dodged the blown heater hose with a new bit joined to the old bit with a peice of copper joining the too, the old peice burst while he was driving and cooked it, thats when i got hold of it, not knowing how hot he had go it i replaced the hose properly started it up and it had a bad miss then pop out came a welsh plug. he had totally f**k it so i got him a good low k's motor dropped it in and replaced the entire cooling system (well nearly), and this is where i am at (back to the top post).

Some thermostats have a plunger that blocks of the pipe that goes to the heater (or converter in your case) when it opens. Perhaps the thermostats you've tried have this on them.

or maybe just repalce the heater tap again, perhaps its blocked? (only $10- part)

well the set up on this has a T peice inplace of the coolant temp sensor one side of the T goes to the sender the other to the converter, could that be a problem there ?

Have you purge the cooling system of air. sounds like the only circulation you're getting is the front of the block. thats one of the main cause for warped heads due to coolant just circulating the front but leaving hot spots at the rear of the block.

Think of it as air trapped in your brake line. not much pressure on the brake pedal cause air is just getting compressed between the fluids. giving it that spongy feel.