brake servo hissing

[geoff]

I have just started hearing a hissing sound from where the brake pedal rod enters the servo. This is accompanied by a hestitating of the engine.
Are we talking about the need of replacing the servo ?
regards
geoff

[rridge]

Diagnosis by part replacement is particularly inconvenient on the brake booster. Two other air leak suspects are the check valve on the front of the booster where the vacuum hose connects and the vacuum hose itself. Put a helper in the driver's seat while you get your ear closer to the booster while the brake pedal is depressed. But yes, the rubber diaphragms inside the booster housing have a finite life.

[courtenay]

I have just started hearing a hissing sound from where the brake pedal rod enters the servo. This is accompanied by a hestitating of the engine.
Are we talking about the need of replacing the servo ?
regards
geoff

Yes. Use vise grips to Pinch the vacuum hose leading to the booster. Then put your foot on the brake. If no whoosh and no change in idle, the unit is pooched. See my booster replacement thread in the General Maintenance section.

http://www.fiatspider.com/f15/viewtopic.php?f=9&t=39014

[SteinOnkel]

Text book example of vacuum leak at brake booster.

Enjoy. It's a pita to replace, just like everything else on these cars.