The throttle body heater runs warm coolant through the throttle body to help warm it. It is mainly helpful for people in cold weather areas.

Sourced from here:WHY Heat The Throttle Body!?

There's two reasons we want to heat the incoming air. The first is that the atomized fuel will mix with warm air better than cold air. This was actually more important with carburetted engines rather than fuel injected engines.

The second reason is to keep the throttle chamber from freezing. Yep, that's right. I said freezing. As in ice forming inside the throttle chamber.

Anyone who lives where it gets cold in the winter has heard of "wind chill". It'll be 30° with a wind chill of 10°. As the air moves through the throttle body, the same wind chill affects the inside if the throttle body. Under certain conditions, such as high humidity, condensation will form inside the throttle body and the moving air will freeze it. This ice will keep building up until it chokes off the air supply and the engine dies.

It heats the throttle body. Hence the name.

Or it could freeze in the wide open after a nice cold trip down the highway

Replaced this recently on my 03. Pull the two small hoses off, remove throttle cables, remove vacuum lines on throttle body, remove screws and pull entire throttle body. The bonus is, you probably need to clean the TB anyway, so it's a great time to do it and makes the heater replacement a piece of cake. Use the right tools to remove the small screws on the heater... wouldn't want to strip those. Otherwise, it's a very easy to do job and you can kill two birds with one stone.

Hope that helps.

anyone have any idea on how cold it would actually have to be (ambient) for this freezing to take effect? I assume it would need be VERY cold...? just curious, as I have taken a couple of trips where it was several days around 0 f. and have seen no issue w/o the tbh. any idea?

Dusty,


as stated earlier it have a lot to do with the wind chill factor, I would assume on a 30 degree trucking 65mph that your wind chill factor would be well below the 30 degree ambient temperature.

Not quite this.

Exactly this. I know someone that this happened to, as a result of bypassing their throttle body heater. It's a good thing he wasn't driving an automatic.

Not cold at all, in fact, it can happen at slightly above freezing temperatures while cruising at highway speeds.

wow. I would have guessed -20+, given the heat produced under the bonnet.

It is true this is unlikely to happen on a large throttle body like on a rover, but a smaller throttle body or carb especially, this can and does happen.

http://www.ultralightnews.ca/bing/im...img_ch_ice.jpg

My uncle had a farm tractor on which the carburetor used to freeze in the middle of summer. You would see the ice forming slowly around the outside of the carb until it was totally encased in solid white ice. I mean for us kids this was crazy as it was happening at 70-80°F during the day under the sun, on a very hot engine. Now I know it was mainly caused by the evaporation of fuel in the carburetor throat. What happens is that in order to go from liquid to vapor, the fuel needs energy, and it takes it from the surface inside the card, thus cooling the carb and causing it to eventually be colder than the outside temp.

Nowadays with injectors the evaporation occurs only past the injectors so the above explanation doesn't apply, but the sudden drop in air pressure past the butterfly in the throttle will cause the air to cool a little. It's the same principle as when compressing a gas, for example in a diesel engine. The simple act of increasing the pressure inside the cylinder will increase the temperature at the same time to the point of causing it to burn. So with the right conditions in the throttle body such as the position of the butterfly, air temperature and intake vacuum, the temperature of the air could drop significantly.

As for the wind chill factor explanation, I think it doesn't apply to the throttle body because there is no evaporation involved at that point. The reason humans feel colder because of wind is because the humidity contained at the surface of our exposed skin evaporates faster because of the wind, and to evaporate it requires energy which is found in our body. This is why we feel cold when we get out of the shower if there's a slight breeze. In the old days we referred to the wind chill factor as the wet bulb temperature. But if there's nothing evaporating like in the throttle body, the wind chill factor doesn't apply.