Clutch Problem?

The coolant loop through the throttle body is used to warm the body. For cold climates so you don't get vapor lock. I disconnected that coolant loop bypassed the throttle body and barreled the little coolant lines together when I first bought my 07. That was 17,000 miles ago. A Rad heated throttle body is not needed down here in Florida. All it will do is stress that expensive throttle body & motor with 190 degree heated water. Plus the car runs really good in the summer with a cool body. I had no issues inducing air into the coolant system. Very little coolant leaked out. Maybe a tablespoon.
Now in Minnesota your screwed without a heated throttle body.

 

The only way you will know if there is any impact is if the throttle plate sticks due to some ice buildup

The more important question is what do you gain by bypassing the coolant to the throttle body?

 

Its debatable, I don't notice a difference, but car makers work at bringing cold air into the intake, so it makes sense to me to keep the intake itself cool. This thread claims 1-2 hp in a saturn.
Step-By-Step - 3.5L Throttle Body Coolant Bypass (with pictures) - SaturnFans Forums
I had thought of adding a valve controlled shut off for the coolant line, to adjust for the seasons, I will if required. I do like to modify.

Here is a lengthy priuschat thread with more info pro and con
http://priuschat.com/forums/gen-ii-prius-modifications/42065-tb-hot-water-bypass.html

I personally do not do much high speed driving at freezing temperatures, so its also based on my driving needs. I also figure, whats the worse that will happen? The throttle plate freezes up, the engine doesn't run right (I'm well informed about ua by now) I pull over to the side and wait until the ice melts, though I do suppose it could harm the throttle motor. I'm also for the most part the only one who drives the car, and so I can take a few more risks .

I will make a point to look for any icing in the throttle body next winter. One other consideration, I often will drive an older backup car during rainy /icy /snowy weather thus avoiding the times this would happen. The prius is not designed for 100+ miles of mud roads.

Additional interesting info found here
[ame]http://en.wikipedia.org/wiki/Carburetor_heat[/ame]

 

I've had carb ice in airplanes, and it's no fun. You don't need freezing weather for carb ice. You need warm enough weather to have water vapor in the air, which gets frozen in the throttle body by adiabatic cooling. That won't happen if it's really cold or really hot. It's the humid in between that will get you.

Tom

 

In non-hybrids with Otto cycle engines, colder air intake does increase wide open throttle power but also reduces partial throttle fuel economy by increasing air pumping loss. The vast majority of driving is at partial throttle, so some hypermilers seek warmer air intake year round.

The Atkinson cycle engine in the Prius reduces the later effect, but does not eliminate it.