Ok so not brilliant news ..
It lost coolant driving back from were you bought it ( private sale ? ) and it over pressurises when run upto temp.
The temp .. 100 is too high for a car at idle so you have a fan issue or you have a coolant circulation problem .. there is one other but ill leave that till the end.
Lets say there is an airlock .. coolant wont circulate and it will over heat .. that will push coolant out the cap .
A faulty water pump or thermostate will do the same .
A faulty cap .. basically not holding pressure will do the same .
The last one .. which you dont want to hear is a headgasket failure and having x2 headgaskets it might be tricky to find which one .
I will say its very rare , in fact i havent seen one go this way .. when they normally go it lets coolant into the engine and you get D chunk ... again ive only ever seen a handfull in nearly 15 years .
First thing is replace the cap .. and get the system bled out.
Then get your garage to do a "sniff test " .. its a device that detects combustion gasses in the coolant ... if this is ok then thermostate / water pump is were i would be looking next and im kinda leaning towards these due to the temp the car got to ..
Btw .. 100 is not an over heat .. 120 is ! .. 100 is also the boiling point of non pressurised water !!!
Sorry for the bad news but i always try and list out what a fault can be .
It lost coolant driving back from were you bought it ( private sale ? ) and it over pressurises when run upto temp.
The temp .. 100 is too high for a car at idle so you have a fan issue or you have a coolant circulation problem .. there is one other but ill leave that till the end.
Lets say there is an airlock .. coolant wont circulate and it will over heat .. that will push coolant out the cap .
A faulty water pump or thermostate will do the same .
A faulty cap .. basically not holding pressure will do the same .
The last one .. which you dont want to hear is a headgasket failure and having x2 headgaskets it might be tricky to find which one .
I will say its very rare , in fact i havent seen one go this way .. when they normally go it lets coolant into the engine and you get D chunk ... again ive only ever seen a handfull in nearly 15 years .
First thing is replace the cap .. and get the system bled out.
Then get your garage to do a "sniff test " .. its a device that detects combustion gasses in the coolant ... if this is ok then thermostate / water pump is were i would be looking next and im kinda leaning towards these due to the temp the car got to ..
Btw .. 100 is not an over heat .. 120 is ! .. 100 is also the boiling point of non pressurised water !!!
Sorry for the bad news but i always try and list out what a fault can be .