2013 CooperS, no problems to date. Suddenly noticed that I'm not getting much heat--wondering if anyone has ideas, diagnostic/repair-wise. Here are the details:

1) All of the following seems to apply whether or not I have temperature control on or off.
2) The car takes an unusually long time to start blowing warm air (even then, not hot like I’m used to with this car)
3) With temperature control on, it seems to act (mechanically) as normal: when the engine first starts, with the thermostat set at , say, 74 degrees, the fan stays on the lowest level—presumably to allow the engine to heat up. A couple of minutes later, per usual, the fan speed increases—but it continues to blow cool or, at best, lukewarm air.
4) A couple of minutes after getting up to highway speed, the air blown gets warmer—though not up to usual hot level I’ve come to expect with the car.
5) Then, when I come off the highway and idle at a light, the air returns to the cool/lukewarm state.

Any thoughts or suggestions are much welcomed! Thanks, Mike

 

Is there coolant in the car? Has the cooling system been serviced recently? Has it been bled properly?

Could be a large air pocket, lack of coolant in the car, or a clogged heater core.

I know we've had to clean out the cabin temperature sensors on multiple gen one cars due to being full of dust and crap, you could be having the same issue.

 

You could have a coolant leak from a thermostat housing crack or just low on coolant. Have you seen coolant on top of the transmission housing or leaking underneath. Its the expansion tank up front on the driver side have coolant in it and up to the "Min" mark.

 

Most likely an air pocket.

 

Yep with air pockets there's no way for heat to travel to the heater core if there are is air trapped in there, water is 20 times more efficient at transferring heat than air alone which would explain the Luke warm air. It's common to have air trapped in all places like the heater core if there is or was a coolant leak.