yo what up peeps new to the forum my name is Lupe, i own a 86 fc that i just bought like 2 months ago, i also own a 95 240sx that is currently in the shop getting painted with s15 front end conversion, bomex front, D-max rear and sides, and i got a 99 accord as a daily driver. I love my fc pearl white all stock good condition but it overhearts occasionally the guy i bought it from changed the water pump and radiator but the radiator isn't oem it has a radiator cap and he said the oem didn't have a radiator cap it was closed off, but he put a t-hose from the radiator to the overfill tank and somewhere else i gotta check i forgot buy if the radiator cap is on it builds up pressure and overheats. If i take off that cap it wont overheat but water spills every where under hard acceleration, im not sure how those lines are supposed to go from the overfill and radiator i think thats the problem, im new to rotarys so im not sure please help me out.........Thanks

 

Change the cap for an OEM one.

 

definatly get a new cap.. radiator cap will increase boiling point of your coolant and release pressure

 

i'll try that but why would the cap build pressure in the hoses

 

because the cap has a "breaking point" sort of, and the aftermarket one you have might have a higher breaking point than the oem one, retaining pressure in the coolant system, and increasing the water temp, thus making it boil.

 

Actually, increasing the water pressure will make it harder to boil. More coolant pressure should not increase the water temperature, but it will increase the boiling point of the water, making it harder to boil.

How are the "T" hoses connected? If one end goes to the thermostat housing and the other goes to the radiator, you might try leaving the higher pressure cap in the radiator and putting lower pressure (stock) one in the thermostat housing. This should cause your burp point to be at the highest point in the system (ideal).

I may have misunderstood you, but I think this will help.