Need Exorcist!! Overheat devil in a 93 240sx. Please advise.

[trackslut240]

ok, car is a 93 240sx with ka24de, manual trans, 203k on car and trans, three weeks ago the stock oem radiator blew off, it separated from the core, meaning the plastic part stuck on the core of the radiator, i blamed the nismo cap(higher pressure, older radiator,etc), car has dual flexalite setup, ebay intake, stock exhaust, the fan is hooked up to the small ac fan connection, so it goes on when the ecu thinks the car is overheating, aftermarket temp gauge sender (installed in the bleed screw(burp screw)).... sorry for the long post, ordered a koyo twin row aluminium radiator, bled the radiator system, car ran fine temp on gauge sitting a little below half, 210 on the aftermarket gauge(its a crappy ebay one, i am sure its not right, but close) ran good for three weeks, turn on the dual fans by turning on the defroster, temps are brought down to 180 or even lower sometimes in traffic, ambient temp being in the upper 30F, this sunday temp shoots up and i panic slowly, take the exit and look for a gas station to fill up coolant, thinking it blew a hose, stuck thermostat, do a quick check, no leak, overflow tank at max level, totally stumped, decide to drive it home, cabin heater does not blow cold air, now i am thinking its a stuck thermo, accelerate gently then idle and cruise, temp goes up on accel, down a little on decel or idle, take the bottom hose off the engine side, open the thermo stat housing and no thermo!!!! so i put in a thermo, after testing it in a water pot on heat, the valve opens when hot, closes when cold, apply gasket sealer and put the thermo in, the pointy part pointing to the radiator, change the water pump too, might as well, installed new belts, an underdrive pulley, burp the system, lifting the front, thru the bleeder hole , drive out and car sits at 180 for sometime then temps start climbing, no heat in car heater, heater starts to work after sometime,its hot, so that means that there is flow, temps sit at 250 to 270, dual fans automatically running all this time, decel cools a little, idling dont help anymore, top of radaitor and top hose is scorching hot, bottom tank of radiator and bottom hose is cool, fans blaring, not too hot air blowing thru the radiator though, hoses were squeezed before startup and coolant moves in radiator, assuming no blockage, once i arrive, the hoses are harder to squeeze being pressurized, no oil in coolant, no coolant in oil, car runs strong and no missing, any ideas and input would be appreciated, sorry for the long post, checked the front of the radiator core for bags, birds etc nothing, totally stumped, i have searched but have not found a definitive answer, tried all that others have, except back flushing, will do that this monday, THANKS ALLnow i am using the stock radiator cap, not the nismo,

[teddy]

I don't have a definitive answer for your problem, but seeing as you're in Chicago, its cooler out, which is weird that your car is overheating with a Koyo/dual fan setup. You could try a reduced coolant mix, stepping it to a 60/40 water to coolant mix, or even a 70/30 to see if this helps. Try adding a bottle of redline water wetter. The only other thing I can think of that you haven't done is that a coolant passage somewhere might have some kind of blockage but I don't know why. Your water pump functioning fine?

[trackslut240]

i have diluted the coolant down to 70 30, used a bottle of water wetter, installed a brand new water pump, blockage....hmmm....., some kind of blockage somewhere, maybe even in the radiator, which might be wierd coz that is a lot of rows on the koyo radaitor, bottom hose is cold, top hose is very hot....thanks for the input, i seriously think i need an EXORCIST..... will back flush the whole thing....

[trackslut240]

problem seems to have gone away for now, must have been an air pocket, still needs a radaitor flush, coz i am not satisfied with the outcome... could an air pocket come into the system after three weeks of use of a new radiator? can they come up after a longer time of use after bleeding the air out of the system?? thanks for the inputs everyone....