[marc999]

I am experiencing issues with overheating and I'm wondering if it's related to the water pump or the thermostat. Here are the details. Please help !

the current outside temperature are just below freezing right now.

The car will overheat and the heater won't blow anymore hot air when this happens.

8:10 car drives normally and the coolant temperature is around 90C. The heater start blowing cold air.
in traffic, outside temperature is -2C and the radiator fan is ON
8:11 coolant temperature is at 96C
8:13 coolant temperature hovers between 99 and 104C ( driving 40km/h )
8:14 coolant temperature rises from 106 to 109C
8:15 coolant temperature rises from 114 to 120C
8:16 coolant temperature reaches 125C and the car goes to limp mode. I stop on the side of the road.
8:17 stopped on the side of the road, I turn the engine off and back on a minute later and the temperature hovers between 82 and 87C
8:20-30 drove to work while the temperature hovers between 80-89

Do you think it's the water pump or the thermostat ? Why does it drop back way down when I turn it off and back on ? Just trying to change only the needed parts to save costs. I've read a bunch of threads on here and I haven't seen anybody mentionning the heater blowing cold air.

*** UPDATE 2018-11-28

changed the thermostat (only) over the weekend hoping to fix the issue.
Still not fixed. Car goes to limp mode after 15-20 minutes of low speed driving (40-60 km/h)
before it starts overheating, I loose the hot air coming out of the vents (it's winter here)
when it goes to limp mode, a quick off and on of the engine will bring the coolant temperature to normal and the hot air comes back in the vents.
Last night I noticed the fan would up and down every 30-45 seconds while idling in the laneway.

coolant was changed and bleed while doing the thermostat. The fan works and blow really hard and the pump sounds ok (while I was doing the bleeding procedure)

*** UPDATE 2018-12-10 ***
after changing the water pump, the issue is finally fixed.

thing to keep in mind:
-if the fan is acting up if the car is not even overheating, it points to a faulty pump

-the coolant was flowing through the over-flow hole in the tank but kinda smoothly. When the pump was changed, the over-flow was flowing noticeably faster and with a lot more pressure. Almost spitting out at times.

-When doing the bleeding procedure (max temperature / min fan speed / accelerator 100% for 10 seconds) the sequence would start normally and then the fan would start full speed and wouldn't stop for the rest of the bleeding procedure. Actually the bleeding procedure wouldn't stop on its own even after 20 minutes (at which point I stopped it myself turn the car off)

- When doing either thermostat or pump, do both. They usually die in the amount of time / mileage and it's a pain to get to and change (I did that twice). Since I was doing it myself it was only my own time that I was *wasting* but at least I didn't have to pay somebody to do it.

-while you have the pump and thermostat out, check that the oil pressure control valve is not leaking. It is located in front of the engine right above the water pump and it's a pain to access when everything is in place. While the pump is out, it's much easier. The o-ring is worth about $8 CAD and is fairly easily replaceable. Mine was leaking.

Thanks to all of responded. Next up is the valve cover gasket sometime later in the winter or in the spring. It's already leaking...

thanks

Marc