Is this normal?
 

I was in the car the other day for the first time in HOT weather, it peaked at 110. drove across town and saw the temp gauge was almost halfway betwen the middle and hot but staying very steady.

Turned the car off, then 10 minutes later had to run out for some ice.. started it and it was at 3/4. Didn't want to drive it, so I took a friends car. Is it normal for it to run hotter in.. well.. hotter weather? I understand cars get hotter once you turn them off. On the way there it was mainly 55mph plus so I thought it should have stayed in the middle, but it wasnt and like I said steady at that mark.

Should I do a coolant flush? I opened up the overflow cap and noticed gross yellow brown gunk. I did top off the system with dexcool when I changed the thermostat back in December. Heater core is also bypassed. Lately I've heard a light hissing sound after turning it off. I'm thinking it may be the hose clamps on the heater core bypass. I dont have those quick connect fittings on them, just the hose clamped onto the pipes. Bought two quick connects, but havent installed them yet, will do that when I flush.

And if my research is right... if you have air getting into your system with dexcool it can cause it to gunk up like that.

My first thought was I was loosing oil into the coolant, but the oil level is right where it should be after I let it cool down and checked it.

The engine bay itself seemed really hot too. But this is the first time in weather above 85 or so, not sure what to expect..

Thoughts, Ideas? I know I'm going to need to do a coolant flush. Overflow looked pretty grody. Anything else?

are the cooling fans working? sounds like it could be possible they aren't if the car cools down when you start driving it.

you said you topped with dexcool and there was gunk? was there dexcool in there initially?

Both fans appear to operate fine.

The stuff that was in there when I did the thermostat, I'm not sure. It certainly didn't look green. And there was a little bit of that crap in the overflow when I did the thermostat. I topped it off with 50/50 premixed dex cool. This is the first time I think I've checked it since. That was December.

I'm thinking it may have had old regular coolant in it now. Hm. The only thing I'm going to be able to do is drain/fill, drain/fill since I dont have a garden hose at my apartments to hook up. Should I take the radiator completely out of the car and bring it to my car wash and power wash it out?