Inconsistent Heat output until fully warmed up

[GTOchris]

Hi,
The previous owner replace the radiator at some point before I bought this 2 years ago. The coolent level is good and of good quality.

With cold starts, climate can be in auto or manual, the fan speeds up based upon when the engine starts to produce heat however unless I'm moving the output can become quite cold. If I hit the highway I can get and keep consistent heat however if I slow down for traffic or a light, I can loose heat and it starts blowing cold. After it gets good and warmed up the heat stays strong.

Should I start with changing the thermostat? Or maybe blow out the heater core?
-Chris

 

[ARunner]

If you are positive you really do have the coolant completely filled, then yes I would suspect thermostat. However, an open thermostat should also mean it's takinf the vehicle a LONG time to warm up in cold temperatures like we have been having. Likely not even getting up to operating temp if completely stuck open. Could be just partially stuck though.

 

[sigepbiker]

[MENTION=106920]GTOchris[/MENTION] did you get this fixed? I'm having the same issue.

 

[Sungod]

I would guess thermostat along with bad clutch fan that is frozen. The clutch fan is an easy check. It should spin freely by hand when it is cold meaning that you can put a piece of masking tape on a blade that is attached to the shroud. This shouldn't break until the fan heats up and engages. If the tape breaks at start up and the fan doesn't spin freely meaning it is permanently engaged, it is bad. It would be drawing in cold air across the radiator when you are stopped. Typically this shouldn't be much of an issue because your thermostat would stay closed blocking the flow of coolant to your radiator, but if your thermostat is bad, it would allow for cold coolant to flow through the block keeping the coolant that is flowing to your heater core cooler longer.

If this were mine, I would start with the clutch fan check and then replace the thermostat. Thermostats are cheap and easy to replace especially with the 6cyl. The clutch fan if bad is easy with the right tools, and isn't terribly expensive.