Join Date: Jul 2010
Location: Pittsburgh, PA
Feedback Score: 0 reviews
It sounds like your vacuum pump is weak. 10 CM is about 4", that's low. Funny thing is, mine may be weak, too. I just tested mine at the tree for comparison. I get about 16" initially. It drops to 10" the first time I apply the brake, then slowly recovers to 16". If I pump the brakes rapidly, I can drive it down to about 5", and it takes some to recover. The longer I pump, the harder my brake pedal gets, due to lack of vacuum. I've never noticed a problem while driving, though.
'89 F250 2WD XLT Lariat Supercab,
7.3 IDI, C6, 10.25" 3:55, dump bed.
Mods: Gear Vendors overdrive, ATS 085/088
"Frankenturbo", boost and EGT gauges in pod,
K&N air filter, cold air intake, filter minder, rear
work lights, 'monback beeper, pintle+ball hitch,
brake controller, CB.
Wish list: 130 amp G3 alternator, front hitch,
new hood, fresh paint.