well, if by fluid u mean coolant than yes. If coolant is leaking, there wont be anything to cool the engine temperature. Replace the cap, there very cheap.
Sound like ur head gasket has a crack or is blown need to fix it ASAP
Blown head gasket or cracked block.
your head could be cracked you will not notice the water lose when you car is running see if the water is coming out of the tale pipe
A seal, or hose is leaking or you have a cracked carb. Check the fuel filter and make sure it's not loose or cross threaded.
Coolant entering the combustion chamber. You have a blown head gasket or a cracked head. Warning: Stop running this engine or serious damage will occur.
Bad head gasket? Cracked Head? CRacked block?
Cracked head or bad head gasket.
The head gasket or actual cylinder head is cracked.
Steam (White Smoke) coming from the tailpipe is the #1 indicator.
If you have coolant coming out of the exhaust. You have either a blown head gasket, a cracked head, or a cracked block. This can totally ruin your motor.
Cracked fuel hose(s); bad fuel line connections; or cracked filter housing.
White smoke is a good indication you have a blown head gasket. And/or a cracked head. Did you noticed, when it happened that the engine started running rough? Best i can do with little info.