So I was initially having intermittent over heating issues (about once every 3 weeks or so). I put a new water pump in and thought that I was in the clear. The truck is still getting upwards of 220 degrees and the thermostat is not opening. Heat comes on initially but then disappears. Both heater hoses appear to be cold. Well the "in" hose is warm initially but then I lose heat and it goes cold.
I shut the truck off and began venting the reservoir cap and all the sudden it was like the floodgates opened. I could hear the rush of coolant through the upper hose. Heat was restored and the truck runs fine. Any ideas on this? Could I have possibly gotten another bad thermostat. This one is new (Stant superstat 195 degree)
I don't know what to do anymore!

 

Did you maybe put it in backwards?

 

No. Thermostat in, springs down, gasket on top.

 

and it's an 02 F250 Super Duty 5.4L 4x4

 

I just don't understand why the heater hoses are cold, then the thermostat opens, they heat up, I get heat and everything is dandy. Does the coolant have to flow that way for some reason? (other than heat). The system should still work with out heater hoses and a heater core (minus having heat) should it not?

 

Clogged Radiator? Wow hard to tell. I know head gasket issues do weird thing with temp..Either way when the thermostat see's temp it should open unless pressure keeping it closed...Do you have a infrared temp gun you could shoot at the therm housing or block? Shouldn't trust truck gauge..

 

Did you buy a cheap parts house thermostat? ExxV10 had a similar issue with aftermarket parts, Is the cooling fan working correctly?

OEM Motorcraft is the only good thermostat for these trucks.

 

It's a Stant Superstat 195 degree. I have read that the motorcraft part is all that works for these trucks a few other places (and heard it too). Cooling fan seems to be working (in that it is spinning). Fan clutch appears to be working too, though I didn't change it when I did the water pump

 

Might want to take it to a dedicated radiator shop. I have one close by that is low tech and not the taj mahal but he knows his stuff.

 

Start with an OEM motorcraft stat

 

I'll start here. I keep thinking the worst. Could this be a head gasket problem? Once everything opens, it runs at temp forever.

 

Another question, when you test the thermostat (in water), when should they open and how much? I have heard mixed answers

 

So apparently it helps to make sure the system is full of coolant for proper function. I couldn't expect me to have heat and the thermostat to open when it should when i was 1.5 gallons low. Live and learn I guess. I got so tied up with the burping the system that I forgot to refill it. When I did it just kept drinking it down. Took it out for a spin and I had heat within 5 minutes and the thermostat opened at around 206* according to my device plugged in to the OBDII port.

 

Awesome! Now get do driving and not worrying!