Unique Heater Problem

No heat at idle in parking or drive (both with warm and cold engine)
Heat only while driving
Very high heat on turning

Can't be thermostat. Coolant is a couple of years old. I am confused....

YOu were here before but can't remember year and engine type and not shown in your profile .....please specify. However, as soon as someone comes with freak heater problems, I suspect a 3.1/3.4 with a blown head gasket...but I'd be happy this is not the case....
...after checking your previous posts.. 98 MOntana...emm...same reply. :frown:

Sorry, it's a 98 with 3.4L with approx 160,000 miles. I don't think it's a head gasket because there is no loss of coolant or smoke out the rear. Engine temp however is constantly going up and down. Not overheating, just fluctuating.

sounds like the beginnings of the infamous intake gasket/head gasket problem. My 99 went to 144k miles until the head gasket finally gave up. We played the inconsistent heat/add coolant game for a few months before any signs of white smoke coming out the tailpipe.

SO, how hard is it to replace this head gasket. I am mech inclinded with most tools. I have rebuilt engines before. How is the space problem? Do you have to pull the motor out or something?

My brother had his (...a 2002) done last year...said all the gear for wipers must go out first to make room but job is done "on the site". Others who did it will add more details, for sure.