iv got a 91 240sx super hicas thats overheating and i cant figure it out.
it has a new thermostat a new radiator the water pump is working there is no antifreeze in the oil no oil in antifreeze. i did the jack the front of the car up and remove the air bleeder thing like 5 times so im fairly sure its not air in the system. if i idle it it wont overheat and if i drive it it will in less then a mile. unless i get it up to about 55mph and hold it at that speed then it will kind of just stay at whatever temp it is.

so any ideas? something stupid im missing maybe?

 

what makes you so sure that it's overheating? it may sound like a stupid question, but the temp gauge acting up is a common problem with 240s.

 

its getting hot enough its boiling back up into the overflow tank.

 

do you have the clutch fan, or any sort of cooling fans? at about 35mph (i think) or lower the fans are a main component of the cooling process. at higher speeds the oncoming air will aid in the process. also, a faulty radiator cap will cause this problem.

 

yes i have both my fans (clutch fan and a.c. fan) and the clutch fan is working i know. i havent even checked to see if my ac works yet tho so i dont know about the ac fan. i guess ill try replacing the radiator cap and hope for the best.

are the water jackets in the ka24de motors known for getting clogs in them or anything? should i maybe try running a sulfuric or muriatic acid threw the cooling system to try to clean it out? or is there anything that it can harm in the system for that motor?

 

in that case, the only thing i can think of would be; insufficient coolant, a blockage somewhere in the flow (i doubt this to be the case though) or air trapped somewhere. to answer your question, i generally don't use anything other than water to flush the cooling system. i just don't trust those products to react well when used in a coolant system with case iron, aluminum and certain plastics.

 

well i guess ill try a system flush with something mild like vinegar and a new cap. if that dont work i really dont know what to try next... maybe rewire my a.c. fan to run anytime the car is on or replace the head gasket and check the water jackets threw the head. im really getting stumped on this problem....

 

what was that about the head gasket?

 

problem found i think. bad thermostat new out of the box. replaced a old bad one with a new bad one. takeout the thermostat and it runs fine all day long.

 

i was gonna ask if you were sure the new one wasn't installed backwards.

 

yeah it was installed the right way it just wasnt opening. the lower hose wasnt even getting warm when i checked it so i pulled it back out and it ran great. so its time to change the thermostat a 3rd time in 2 months i guess... thanks for the help trying to figure it out tho man.

 

yeah thats true cuz i changed a whole bunch of stuff on mine too n it was just the gauge