A llittle more information might help. What's the ambient temp when you're seeing 110 with the A/C on? Have you had any work done on the A/C lately, i.e. recharge, adding oil, converting to R134, etc.? What kind of driving are you doing - open-road cruising or stop and go city or freeway traffic? Does the fan eventually bring it down to under 100 and shut off?
When idling, try putting the trans in neutral. This removes some of the load from the engine. You could also try putting it in neutral and raising the idle speed (via the gas pedal, of course) to about 800-1000 rpm. This will get a little more air moving past the radiator without adding significantly to the engine load. I've used this on my '86 300E to bring the temp down noticeably on really hot (105-110 deg f.) days here in So. Calif.
I've also been running Evans NPG+ instead of regular coolant for the last 30K miles. It's a nonaqueous propylene glycol coolant that has a boiling point of 375 deg. F and runs at 0 psi system pressure. Check our their website at:
BTW, don't get the NPG and NPG+
is a direct replacement for the coolant in your car. NPG is an earlier product designed primarily for racing engines. It's much thicker and requires different radiator, pipes, hoses and coolant pump.
Depending on where you are and what kind of winter temps you experience, you might want to try a more water-diluted mixture of antifreeze and water if you don't need the freeze protection. The more water in the mix, the better the heat transfer and hence the better the cooling effect will be. I think you can go as low as 70/30 and still have adequate corrosion protection. Check the label on the coolant container. That's another good thing about the NPG+; no water, so no corrosion.
There's also Redline Oil's Water Wetter, which reduces surface tension dramatically to bring more of the water in contact with the internal metal surfaces to improve heat transfer. It can be used with either straight water (usually required for racing purposes) or with a water/antifreeze mix. For me, it was a toss-up between Water Wetter and NPG+ for a while. I checked out every post I could find on various discussion boards and researched them both on the web. I think either one is a good way to go, but I liked NPG+ better for a number of reasons.
Here's a link to Redline website:
All in all, though, 110 deg.C isn't going to hurt anything in your engine. That's why the red zone starts as high as it does.
This is from a previous post by tkamiya:
T-stat will start to open at 85 to 89C and fully open at 102C
Fanclutch will cut in at 96 to 104C AT THE CLUTCH
Electric fan will come at full speed at 107C and off at 100C
A/C will cycle at 116 to 118C and fully shut-off at 119-121C
Pressure cap will open at 130C
Hope this helps.
Disclaimer: I have no connection with anyone who makes or sells any of the products I discuss in my posts. These are just my personal opinions. Some are based on my personal experience and some are not.