NO heat and Overheats when idling or going under 40 miles an hour

Asked by Sep 24, 2015 at 11:49 AM about the 2006 Pontiac Grand Prix

Question type: Maintenance & Repair

I have replaced the Water Pump, New Radiatior, New SuperCharger, New Coolant system all together, around this time of year after using the AC all summer, can't get any hot air, and then it starts to overheat if not going at least 40 miles an hour or idling.  It will boil back into the overflow tank.  I am at Whits end on what to do and don't want to replace everything again.

6 Answers

7,085

check the thermostat

Thermostat was replaced along with the radiator cap, radiator, water pump, supercharger, anything with coolant going through it.

7,085

is the Freon topped off

Don't know, the AC works fine, just no heat, will that prevent the heat?

2,815

Make sure all the air is bled out of the cooling system using the bleed valve on top of the thermostat housing.

3,625

And, most obvious of all, but easily overlooked, make sure the cooling system is actually full. It's either not full or there's air trapped in the system. Really no other reason for a new cooling system not to work.

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