I was looking over some pics I took from the 20th and noticed that the brake master cylinder in the original pace car is a little odd.

It seems to have an added spot with an extra switch behind the fluid bowl, anyone know what it is or what it's for?

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Could be a brake lights switch.

My guess would be a redunant (sp?) sensor/switch to the one mounted on the output side of the master. That way they could monitor problems both before and after the master. It looks like the wires lead back and join the normal sensor wires.

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quote Originally posted by fierohoho: I was looking over some pics I took from the 20th and noticed that the brake master cylinder in the original pace car is a little odd. It seems to have an added spot with an extra switch behind the fluid bowl, anyone know what it is or what it's for?

The Indy had a HydroBoost braking system installed. There is an additional line not visible in this picture that leads to the space inside the fender ahead of the left front wheel where the pump is located. The thing screwed into the master cylinder is likely a pressure switch that triggers the hydraulic pump inside the fender. You'll note there's no vacuum booster. The SD4 engine probably didn't develop enough vacuum for regular vacuum-assisted boosting to work properly.

JazzMan

[This message has been edited by JazzMan (edited 07-24-2003).]