Afternoon All,
Setup:
1990 Mini
Brake Servo - Bulkhead mounted with twin output master cylinder to brake bias valve (standard).
Servo rebuilt with new diaphram and seals, vacuum line attached to Inlet Manifold.
Entire brake setup new from Servo onwards, New lines, calipers, drums, flexi connections, Briaded lines from Master to Bias. I did rebuild the servo to try and fix this problem but it has not worked (new diaphram seals etc).
The top inch or so of my brake pedal is very airy and doesnt provide any braking power, past this point the brake pedal is firm and the car stops as normal. This is consistent when the car is running, however the pedal is firm when the engine is off.
Ive bled and bled and bled the system and there no air in it.
Ive been around the servo and used brake cleaner to hunt for any sort of air leaks in the system and the car has not changed idle at all.
Sometimes when pulled up at traffic lights and on the brakes, the idle will hunt slightly indicating there is a leak or something changing the pressures in the inlet somewhere, when on just the handbrake the engine idles fine.
This afternoon ive disconnected the vacuum line from the inlet and taped up the banjo bolt on the manifold and gone for a drive. Pedal is heavy with no movement before brake force is applied, confirming that the system is bled correctly.
Am i missing something here or is there an issue with the Servo itself, its almost like when the engine is on its pulling a large amount of vacuum onto the servo, so the initial press of the pedal is just picking up the slack of springs in the system until the pedal plunger in the servo reaches the servo diaphram.
The engine is very tuned, Bored/Cammed/Ported and at around 90hp, would this be causing excess vacuum on the servo pre engaging the brakes?
Worst comes I will purchase an older pedal, double spring and a vertical master cylinder and ditch the Servo, obviously letting my insurance know, bonus right leg workout.
Any help would be great, thanks!