Nissan Repair: nissan frontier 2000, coolant loss, radiator fluid

Question
QUESTION: the truck was in amazing shape and we changed the oil often but somehow the gasket caps and heads cracked. there was a leak in the radiator fluid and we used an adhesive product and ran it through the engine. We are not sure yet if it fixed the leak, but now the truck wont blow hot air when we turn on the fan and turn it even all the way up. What can cause the gasket caps to break without over revving the engine? and why wont the heat work?

ANSWER: Kole,

The stop leak has plugged the heater core.  You could remove the heater hoses and backflush the heater core with a water hose and possibly get the blockage removed.  Let me know what a gasket cap is.  I am in the United States and have not lived in the United Kingdom since the 1970's.  If gasket caps are the valve covers they will leak after this number of years.  If you are talking about the tanks on the radiator they are plastic and they fail about every ten years as well.

---------- FOLLOW-UP ----------

QUESTION: thank you a lot! as far as i know, (gaskets, gasket caps, or "spacers" are the "spacers between the engines core, pistons, hoses and other parts, providing a barrier between liquids or explosions and creating a seal even when the object is under great heat or pressure. Made usually with rubber, steel, or plastic. There are also a more specific type of gasket called "head gaskets" which keep anything from getting into the the cylinders.) Let me know what the proper term for them is. The actual "CAP" is the cover around the engine, a long band holding the gaskets in place. If you understand what i am talking about, what can cause all or any of these objects to break besides over-revving the engine? I apologize for asking a second time.  

Answer
Kole,

The headgaskets are most probably the issue.  I would think the stop leak could have solved the issue with them if the coolant loss has stopped.  If the valve cover gaskets are leaking they would need to be replaced.  If there is still coolant loss and you have water in the exhaust then the headgaskets would need to be replaced.  Nissan uses torque to yield on most of their engines so the head bolts would need to be replaced too.