Speed sensitive temperature issues on Northstar

[okccadman]

Driving my 2002 ETC around town with the a/c on from 0-35 stop and start traffic its fine, runs right at 1/2 on the guage.  It will idle forever with the a/c on and stay at 1/2.  Get on the highway or steady cruising 40+ mph it steadily climbs all the way to hot and the "engine hot - a/c off" warning comes on.  Exit the highway and get back to 35mph start stop and he slowly goes back to 1/2 and teh message goes away and a/c kicks back in.  Any ideas?  Air in the system, radiator flow, water pump?  Ive never had a car get hot and cool right back down so quickly.   I know Northstars have head gasket issues but this just seems bizarre to me.  NO antifreeze in the oil andd no oil in the coolant. 

[Dave Shepherd]

Was any work done to the car prior to this happening?

[okccadman]

Had the notorious oil leak repaired.  I may have found the issue.  Looks like it may be an air bubble.  I'm told that Northstars are "self purging" and dont need to be "burped" like some cars.  The Titanic was unsinkable too!  I found it is a common issue for the purge line from the coolant tank to the water inlet can get plugged or restricted causing a similar problem.  This line may have been moved or kinked during the repair.  I will check it tonite.

[TJ Hopland]

Interesting.   So was it the purge line?   Before you got to that part I was wondering if perhaps something like an air dam or deflector was missing or broken and that changed the airflow at higher speeds.   Thats my current theory on why my 73 runs hot going down the road but is 'normal' at idle.  On that car I know that all those rubber and plastic bits are missing. 

[Sweede64]

Check the waterpump belt, (at the end of the forward faced cyl head) sometimes i would com loose, the impeller on the wp can also bee deteriated.