'01 PT Cruiser overheats in drive, but not in park

Purchased car in 2008. In summer '08 I replaced hoses, thermostat, and
water pump. Went through most of 2009 okay, replaced thermostat again
in 2010. My car started to run hot today and I realized coolant was
low. I had to run the heat full blast on the way to AutoZone to buy
the coolant. I put the coolant in and sat in the parking lot with car
in PARK with A/C running full blast. The temp never got above half. It
sat running full A/C for over 10 minutes without a problem. So I put
the car in DRIVE and pulled out to the light. By the time I got 500 ft
away from the AutoZone, car temp was back up above 3/4. I again turned
off A/C, rolled the windows down and ran the heat full blast in order
to get home without overheating the car. Any thoughts at
all?????????????????????

 

I suspect problem with the transmission. Have you checked the transmission
oil level and condition?

 

Take the thermostat out and run the engine without one.

It's summer-time, it's not like you really need a thermostat right now.

I used to drive my '65 Dodge Polara with slant-6 without a thermostat
during the summer.

 

changing your trans fluid and filter might be in order, and flush the trans
cooler (or just blow it out if you have an air compressor). but before
doing that, check your lower radiator hose and make sure its not real
squishy. It could be collapsing from water pump suction while driving.

 

when you put the AC on, it runs the fan which eventually cools down
the coolant. When you drive, if the AC is not on, Fan wil be controled
by coolant temperature sensor. check if your coolant temperature
sensor is working, or just put one in for 5 dollars.