I posted this on the cooling board but I'm not getting any replies.

I'm not sure if the problems are related but they started about the same time. When I'm at a light or at low speeds temp rises to around 200 even with both fans on which used to keep the car at a constant 170. As I pick up speed tempature continues to rise all the way to the red in the span of less than a minute. It'll hold there for a few seconds then come down to normal temp just as fast. The heater blows cold air on any setting.

I've flushed the system, changed the thermostat, CTS and heater control valve with no luck.

 

i would guess that your low on fluid or have air in the system

 

It could be something as simple as needing a new radiator cap! Happened to me

 

I'll go with both guys above. When your fluid is low or there is air in the system, youget that cold air crap out of your system. I'd also change your cap b/c (as you should know) when you service the rest of the system you are supposed to replace your cap. (You all do do that right? ) I only have two questions (for peace of mind of course) 1. Does the heat come on <i>at all</i> after the temp pops down 2. Are you sure you didn't install the thermostat upside down?

 

Thermostat is installed correctly, give me a little credit. On a test drive today after the temp went back to normal I DID have heat. Then as the temp went up again I lost it. I'll go ahead and throw on another cap just to be safe.