Opel Astra H has an electric driven throttle valve. As I know, coolant in throttle valve body would control bimetal plate responsible for warming up. Why can't it control warm up process based on thermo sensor? Why do they need to get the liquid to the throttle valve?

The throttle valve body inlet pipe (55354563) is really flimsy, besides it is designed for one installation only, it breaks if you try to remove it.

For me it looks like an intentional sabotage of z18xer engine.

1 Answer 1


The reason they have coolant running through the throttle body is to prevent frosting in cold weather. If you live in a warm weather area, you can bypass this in most cases. One of the problems with running coolant through the throttle body is it actually makes the throttle body hot once the engine has warmed up.

  • Oh, I doubt that the frosting is a real threat for the throttle, it sits behind the engine and there should be enough heat from the engine to rise the throttle temperature over zero celsius. Besides, I'm actually looking at Holden Astra with this feature. It was specifically made in Germany for Australian market. Why would they care about frosting in Australia? Mar 8, 2018 at 3:43
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    @YevgeniyAfanasyev - You aren't taking into account physics. When the engine is running, there is a large, continuous air flow going through the throttle body. This transfers a lot of heat from the throttle body into the air (think of it like a radiator). Enough heat can be drawn out of the throttle body to bring it below the freezing point and frost will form. This has to do with startup while the engine is cold until it warms up. The reason you'd see it in Australia is two reasons: 1) universal parts; 2) it's not always warm in Australia. Mar 8, 2018 at 11:53
  • Indeed, it's not always warm in Australia. Jun 6, 2019 at 0:27

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