Intermittent Over Heating
 

A few weeks ago I noticed my water temp was running near 225 while cruising along on the interstate on a cool night. Temp fluctuated between 220 & 230 for about 15 minutes then suddenly dropped to the normal 190. No issues until this weekend when I noticed the temp was 225 as I pulled into the driveway on a fairly cold night. Additionally there was no warm air coming out the vents even though the knob was on max hot. Drove to work this morning in 45 degree weather and temps were again in the 220's and no hot air from the vents. However on the drive home, the temp was back at the usual 190 and the vents were providing hot air as expected.


I assume the thermostat is sticking and needs to be replaced but I have no idea how this affects the ventilation system ??

Check the coolant level, sounds like you have an air pocket in the system causing it to spike hot and stop the heater core from functioning.

Your Robispec-Cooler is probably leaking coolant

Have you replaced your coolant with something other than the factory blue supercoolant?
PS: It should be at the very bottom of the range in the reservoir just as it ships from the factory. Did you overfill?

Which would cause a low coolant level causing an air pocket........

No leaks, coolant in the reservoir is mid way between the marks. My logic is when the thermostat is closed obviously no coolant is sent to the radiator but I'm not sure if that would also cut off circulation to the heater core as well. When it did start working, it was like a switch was thrown and the temp plummeted back to normal. Seems like an air pocket stuck in the system would be a more persistent issue?

It all depends. Crack the bleed screw on the heater hose and see if it's straight coolant.