There are many possible reasons for over heating. Did your gauge panel show that you overheated or did you just lose coolant?

You could have a bad degass bottle cap OR you could have failed head gaskets.

FYI:
Engine temperature is not the only parameter that the PCM monitors to determine cooling fan operation. This is the reason that you will see some variation in engine temperature as it correlates to fan operation. The operation/description of the FSS (Fan Speed Sensor) from the PC/ED manual has a fairly good explanation as to how the system "thinks". This is not your traditional engine hits temp X and the fan clutch locks up. The fan speed sensor is a Hall-Effect sensor integral to the vistronic drive fan (VDF). The powertrain control module (PCM) will monitor the sensor input and control the VDF speed based upon engine coolant temperature (ECT), transmission fluid temperature (TFT) and intake air temperature (IAT) requirements. When an increase in fan speed for vehicle cooling is requested, the PCM will monitor the FSS signal and output the required pulse width modulated (PWM) signal to a fluid port valve within the VDF.

Engine begins to defuel at 221 deg. The thermostat begins to open at about 190*F to 195*F and is not fully open until about 215*F to 219*F.

 

So the engine shouldn't reach 235 degrees then? It was around 224 deg but spiked and smelt coolant at that time and the programmer said 235 and was flashing at me so pulled over and checked it out. At the time I was running grill inserts and have since removed them and it seems to run a little cooler now

 

have you checked the front of your radiators to see if there clogged up with bugs rocks or dirt?
the high speed setting for the fan on mine turns on at around 196 deg on the outlook monitor when idling.

 

man....that was a mouth full........very good info!!!!!!!!

 

I smell coolant at about 220 degrees, and the fan comes on at this temperature the guage moves to about 3/4 but the monitor is what I am watching mainly. Just wondering if the coolant coming out of the reservoir is normal at 220? This is pulling up hills with a small rv aprox 3000lbs I don't think it should be puking out coolant....ps no EGR cooler at all so that's not the problem

Thanks for the help so far

 

No it's not normal. Possibly a bad oil cooler or worst case the gaskets have begun to be compromised.

 

My fan stopped working yesterday on my way home while pulling my trailer. It will not kick on and I had to drop the trailer to get the truck home. What should I look for and how do I test it.