Overheating Problems?

Have a 96 Intrepid 3.5L that’s been overheating under normal driving conditions. Replaced the radiator and thermostat. The system is circulating fine after about ten minutes it overflows from the reservoir tank. Head gaskets are fine, water pump, fans, hoses & fuses and heater core are all good. Checked the trouble codes get #21 O2 sensors, and then disconnect the neg lead checked codes again and nothing, then it keeps repeating in this manner. Leads me to believe that there's a wiring or sensor problem, maybe a short somewhere? There is some after market parts, horns from a sound system which the radio doesn't work and alarm wiring all over maybe is might have something to do with it, but I'm not an electrician. Any suggestions??

Have a 96 Intrepid 3.5L that’s been overheating under normal driving conditions. Replaced the radiator and thermostat. The system is circulating fine after about ten minutes it overflows from the reservoir tank. Head gaskets are fine, water pump, fans, hoses & fuses and heater core are all good. Checked the trouble codes get #21 O2 sensors, and then disconnect the neg lead checked codes again and nothing, then it keeps repeating in this manner. Leads me to believe that there's a wiring or sensor problem, maybe a short somewhere? There is some after market parts, horns from a sound system which the radio doesn't work and alarm wiring all over maybe is might have something to do with it, but I'm not an electrician. Any suggestions??
How many miles do you have on your vehicle? It's possible the vanes are wore out in the water pump. Are the cooling fans coming on? Also there's a Temperature Control Sensor in the block somewhere, and fan control sensor in the radiator. Hope this helps!!

120k miles, egine temp is normal it's just dumping coolant through overflow tank...

you may have an air lock and also these engines are very prone to have water pump problems you must be 100% sure your water pump is good eaven at that mileage

you may have an air lock and also these engines are very prone to have water pump problems you must be 100% sure your water pump is good eaven at that mileage

It just accured to me that maybe you should check out the radiator cap, maybe it's weak and not holding the proper pressure.

Pressure should be at 16psi, I'll check, but do you really think the cap could be the problem??

I just bought a 97 Intrepid with a over heating problem. The radiator was blocked and replaced. We also discovered the fans would not come on. Traced it to a coumputer problem. I have ordered a solid state programable fan controller to bypass the oem computer. the sensors mount in a tube that is installed in the upper radiator hose. Much cheaper that replacing the PCM.

Thanks for the advise all. This problem is truley strange! It has everyone stumped!! The system is functioning fine, just for some unknown reason it dumps all the coolant through the reservoir tank!!??

thats what my car was doing. Radiator was blocked. This allowed the antifreeze to get hot and expand beyond normal operating....$300 later running cool (still have the fan issue, however never gets hot to need them, yet)

well just pulled out the water pump, seems to be in good working order.. is it possibly a computer problem? The car has a mid sized dent on the front quarter panel right in front of the computer, may have caused some problems with it...

If the system is not airlocked (The system is under pressure and coolant flows out of the bleeder valve on the Thermostat Neck when opened.) and the engine is not overheating, (Temperature guage NEVER goes to or beyond half scale) then the Radiator cap is not holding theat the correct pressure or you have a possible head gasket problem.

system calls for a 16psi cap, i just bought one, there was a 17psi on it. think that would cause it?

well great got the overheating problem fixed! took it for a test drive and lost the power steering, the res is empty and there was a large puddle of amber fluid on the ground. Funny thing is that the puddle is under the drivers seat!! I can't pin point the leak.... Any suggestions??

Was it the cap????

the 2 most common area for leaks are 1)hoses & 2)pump/rack. I had a hose rupture and at idle showed no leak. wipe everything dry, fill tank, run car & have someone turn wheel and watch for leaks (flashlight helpfull). I was by myself so I stuffed pawer towels around everything and turned the wheel and went back to see the spot on the towel. It was the pressure hose. Lucas ps treatment works, I highly recommend after the repair pour in the whole bottle.

my02r/t how much did that fan controller cost, just wondering cause I had problems with my fans so I hooked them up to a toggle switch.

The same sensor for the coolant fans is also important for others things too. Toggle swicth avoids this and still leaves things incorrect. The coolant sensor tell pcm when engine is warm and ready fpr close loop operation. It will affect cranking since there is no choke it uses coolant sensor to accomplish this. If you disconnect coolant sensor fan should run. If you engage ac fan should run. If they don't then you have fuse bad, fan relay bad, or bad pcm, grounds. Rad cap has to be good. Proper coolant level. Correct thermostat.Also there are 2 coolants switches or sensor, 1 for guage or light and 1 for pcm.

turned out to be the water pump. I have the chiltons book on this model and it really only says how to replace the ps pump, nothing on trouble shooting or the lines...

It was $100. I know, but it is fully independent of the PCM and can be set to different temps between 174 and 230 degrees. Has 3 LED's power, low fan on, high fan on. I plan on installing the lights where the TC switch would be. I plan on tapping into the factory relay (pcm ground) signal to simiply the wiring. My relays & fans work, just no pcm signal. So I will use the factory relays & wiring.

the solid state programable fan controller cost $100. You can set different temps and will work for both the low & high speed fans correctly.