Just got done with a head/cam swap and ud pulley on my 98 c5 and now my car has really high coolant temps and yes I've bled the air out the reservoir and ran the heater to fill the core but the reservoir hasn't dropped an inch. Possibly underdrive spinning the water pump slower? Would swapping to a 160 stat help correct this problem?

 

Have you gotten a tune? You could be running lean.

Otherwise-- yes, 160 stat and fans adjusted to come on sooner .

 

I had my tuner get me a start up tune so it'll idle but it still need some driveability tuned on and my fans are set to come on sooner than factory around 195 I think

 

A 160 stat will only open sooner....Not necessarily allow the engine to run cooler.

 

That's kinda what I was thinking, well I drove it this morning and temps never got about 205 so maybe it just had some air trapped in the system somewhere? Mostly all highway so the water pump was turning faster than at idle with the ud pulley and cooler air across the radiator then yesterday's heat

 

You need to bleed the system from the little coolant crossover up near the throttle body.
Break it there and wait till coolant runs out, then fill the resivor.
See if that helps.
205 is normal operating temp.
Also, make sure there isn't a bunch of junk in the radiator, and in between the rad and AC condenser. C5's will fill with grass, leaves, plastic bags etc in there.

Ron

 

Radiator and condenser are clean I just had them out for the cam swap, I ended up swapping out my stat for a 160 and it's around 195-205 parked, about to make some pulls on the dyno at work we'll see how the cooling system works now