brake booster, master cylinder or vacuum pump? - Ford Powerstroke Diesel Forum
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post #1 of 8 Old 08-06-2013, 05:26 AM Thread Starter
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brake booster, master cylinder or vacuum pump?

So i got my good ole 95 going again finally, and forgot a out the brake issue it had. Back before i pulled the hpop for resealing and before i bought it the guy had the brake master replaced along with the booster right after that at a shop. So the issue im having now is that the brake pedal feels good, has good travel but returns slowly. Slow enough that i had to put a spring on it so the brakes would release at ap light so i could take off. Also the parking brake light will come on sometimes...then go off then flash here and there, which is kinda weird to me. Has anyone else had a similar experience? And where should i start and test?
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post #2 of 8 Old 08-06-2013, 08:40 AM Thread Starter
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Well so far i found someone that said i should have 16 in. Of vacuum at an idle so ill test that whem i get home. What makes the pedal return? Is it a spring in the booster or master cylinder?
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post #3 of 8 Old 08-06-2013, 11:14 AM
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Does the pedal feel like it sort of "sucks" to the floor when you apply the brakes and then "delays" on return? If so, when I had the same symptoms it was the booster. I replaced it with a "zero loss" booster and problem solved. Cheers!

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SOLD - 1994 F350 CC DRW 2WD PSD, 5 Speed, 4.10 LS, SBC Con-O, Baldwin Filter, Tymar HPX Hose, DPPI DP, Bilsteins, $12 AIC, Coolant Filter, Explorer Overhead Console, A-Pillar w/ISSPRO Black Ice, EV Boost, and EV Pyro, Modified Pedestal, Gutted EBPV.
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post #4 of 8 Old 08-06-2013, 11:59 AM Thread Starter
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I will pull thespring off the pedal and try it tonight...thanks
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post #5 of 8 Old 08-06-2013, 04:22 PM Thread Starter
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Well i pulled the spring off that i had on the pedal....and now the pedal does return at a decent rate...it feels pretty spongy and i started it with a vacuum gauge hooked into the line that controls the heater controls and was getting 25-26 in. Hg. (hooked in before the little vacuum filter/modulator on the line) but when i pumped the pedal i could actually deplete the vacuum supply...it would take about 10 sexo ds or so to rebuild to peak vacuum but it would do the same thing everytime....is this normal? I think the pump is working fine after watching it but think im gonna give a brake bleeding job a try first. Any input or help is much appreciated...ill be posting my findings/results until this is cured.
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post #6 of 8 Old 08-06-2013, 04:25 PM Thread Starter
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Oh and i also forgot to mention that the brake light on the dash is still lit...and goes out periodically...i unplugged the e-brake plug as well as the pressure switch on the master cylinder without it going out....any ideas there guys? Could it be air in the master cylinder throwing it off?
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post #7 of 8 Old 08-06-2013, 06:42 PM
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If the vacuum is depleting, its probably the pump (and low vacuum will light the brake light on the dash) or you have a leak somewhere. You should have 17-24 in-Hg at idle. Measure at the vacuum manifold. Cheers!

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post #8 of 8 Old 08-07-2013, 05:34 AM Thread Starter
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Ya it has good vacuum at 25-26 but if i pump the brakes i can draw it down to nothing after 4 or 5 good pumps...and then i can wait 10 seconds and itll rebuild back to good vacuum...i bled the brakes and they seem to be working better. I also found the low vacuum switch and the nipple off the side of it is broken off and someone had just looped the line originally going to it back to the manifold, so im going to be ordering one of those today
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