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Bosch Throttle Bodies: Valve Assembly Removal


Bosch throttle bodies have a number of parts that are easily swapped out like the motor, magnets, middle gear and the potentiometers in the cover. The hard part is the valve assembly. This is a pretty robust piece that probably doesn't need to be replaced but it houses the sensitive potentiometer fingers which can be worn and also damaged very easily.

The simple way to remove the valve assembly is to knock out the plug at the end of the valve and press it out. That would work nicely except the plug is a one shot deal and is destroyed by removing it. As far as I know, there is no place to buy them. For the throttle body in the Ferrari 360, there's very limited access to the shaft from that position.

Another way in: Pry off the cap. 

To take the valve assembly out, another way was needed that wouldn't be destructive to the original throttle body.

Before removing the valve plate from the throttle body, measure the distance between the top of the cover and the shaft on the valve assembly. This is a critical measurement so be sure to get it right. When installing the valve assembly, this measurement must be repeated. The distance between those delicate fingers and the graphite of the potentiometer has to be right or the throttle body will malfunction or not work at all.

This is the measurement I made: 5.66 mm. Like I said, critical. Do this measurement BEFORE removing the valve plate as the valve plate holds the valve assembly at the correct depth.

Here's the reading after removing the plate: 4.62mm. About a millimeter less. This is the distance between the bearing keeper and the bearing. Be careful! This operation requires the protective cover be removed. Who designed that silly thing?

Since changing the valve assembly requires also having another throttle body for parts, one of the parts that can be used is the valve plate itself. The method involves cutting the valve so that it can be used to press the valve assembly out of the body of the throttle body.

The idea is to cut enough off the top of the plate so that there's travel in the shaft and enough off the bottom of the plate to insert some sort of rod or bar to be used during pressing. This has to be a solid bit of steel that won't bend under load. The load to press the valve bearing out of the body is about 500 lbs. Enough to bend a screwdriver.

It's a very good idea to chamfer the edge of the plate that's going to be pressed against (the bottom). The act of pressing will distort the edge of the plate, making it impossible to remove from the throttle body. Adding a slight chamfer allows for the plate to be removed even with slight damage during pressing.

Install the modified plate in the throttle body.

The next thing needed is a way to press down on the sensitive end of the throttle body. I came up with a 3D printed tool for this.

Here's the throttle body ready for pressing. Pressure is applied at the top of the red fixture and two strong steel bars are inserted into the throat of the throttle body, under the valve plate to resist the pressure. The result is the valve assembly moves up and out of the throttle body.

Here's the setup in the press. I'm using two wheel holders as the fixtures.

Not exactly perfectly upright but it doesn't matter. It takes about 500 lbs. to push out the bearing. 

Alternatively, if you lack a press, here's another way.

This actually worked but was a LOT harder and a lot less controlled. If you don't have a press, this will work. Be sure to use jaw inserts that are plastic to keep from damaging the throttle body. It has to be really clamped in hard to resist the pressure it takes to force out the bearing. Be sure to apply equal pressure to both screwdrivers or the shaft may be twisted or bent. When it starts to move, it will get easier when it's nearly done. Go slow and be careful.

Here's the valve assembly after removal.

Note the gap between the keeper (the black circle below the bearing) and the bearing. It's about 1mm. This is from the factory and not caused by pressing the bearing out. Leave the protective cover on. One small mistake and all your work can be thrown in the garbage. Do not touch the fingers!!!

The spring that keeps the valve under tension also can propel the valve assembly across the room. Be sure to have the valve assembly restrained when the valve plate is removed after pressing. The thing will jump and try and commit suicide. It happened to me the first time but the protective cover saved it.

Keep in mind that the shaft of the valve assembly is split and can be bent easily. The screws holding in the valve plate are torx, so no downward pressure is needed when removing them. Try to avoid pressing down on the shaft. Even a slight deformation will render the shaft unusable.

Link to the .step file for the tool:


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