Radiator,car over heats on 1994 Honda Civic

problem:Every 3 days or so i have to put water or coolant in the radiator.someone told me it could have a leak.It was check and no leaks.I accelarated the car and noticed that the radiator was spitting the water back in the water jug, and with the pressure it was coming out the water bottle.I took the radiator to get it unclogged was put back in the car and accelarated again and still doing the same.I spoke to a mechanic and he said it could be the thermostat or a blown headgasket! I check and the car has no thermostat.Does the radiator cap has something to do with that?it has a 1.1 on it. Can someone please helppppp! before i go and buy a new one!!! thanks for reading!!

Asked by for the 1994 Honda Civic
Start with replacing your radiator cap as its a 16psi rated cap and if its not holding pressure then it will spit out coolant, But only change this when the engine is cold about $15 at the parts store
Before going out and buying a new radiator I replaced the cap with a newer one and drove the car for about 15min with the ac on,My car didnt overheat and no water had come out, so yes it was the cap!!The mechanic was telling me yesturday it could be the headgasket and come to find out it wasn't!!!!! so thank you so much for the information!!
my sons car is doing the same thing of every three days replace the coolant .and i already replace the radiator and thermostat.. so im going to replace the radiaor cap. i hope this works! thanks
Thanks for the answers, It was the radiator cap.