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MG MGB Technical - Brake Servo test

just while im thinking about it, this may sound daft but how do i test the brake servo on my 1974 gt. I never heard anything like a hiss from it but the cars has always been the same pedal feel wise and stops the car OK.

I just dont know how to see if the servo actually does anything.
whiskeyfrank

To test your servo's effectiveness, first with the engine switched of, pump the brake pedal several times, 2nd, keep pressing the brake pedal and then start the engine, if the pedal dips then the servo is working. This is the method that MOT inspectors use to test servo's.
Hope this helps.
john wright

With the single circuit brakes and remote servo you do have to press the brake pedal pretty hard to feel further downward pressure when you start the engine. It may be easier to feel on the later combined master and servo as that gives more assistance.

The other test is of the vacuum circuit and that is after the engine has run, switch off, then pump the pedal as if for the test John says. You should hear hissing and wheezing from the servo as the pedal is operated and the pedal should gradually get higher as you use up all the vacuum in the reservoir. This should still happen several hours after switching off. If John's test works, but this fails, then there is a leak in the vacuum circuit and it will be weakening your mixture (which the carbs may have been tweaked to 'compensate' for).
Paul Hunt 2010

This thread was discussed between 12/05/2010 and 13/05/2010

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