ABS to Conventional brakes, where did I go wrong?

Boonze

Registered User
After reading the forums here, i decided to undertake the ABS to conventional brake swap. removed the "abortion" and installed a used junkyard booster from a 92 cougar (clean with no rust) & a new master from the 93 crown victoria. Plumped all the brake lines as instructed on the forum & ran vacume hose from the largest vacume line behind the plenum. Bled about a gallon of fluid through the brakes till i am sure there is no air. Replaced the booster push rod for a longer one & adjusted to 1/16" clearance between the push rod & m/c bore plug. So basically I think I did everything right. So I start up the car & watched the pedal get sucked down about 2-2.5" (to the floor) and was hard as a brick. Soon as i shut the car off I hear a slight "wooshing" sound and watch the pedal return to it's upright position. Otherwise the booster make no noise at all. When I tried to drive the car it acted like the brakes were dragging reguardless of the adjustments to the push rod. I checked that i had good vacume, checked the one way valve (all good). So I am wondering what I did wrong, just bought a bad booster ? or do I need to bleed more or something ? Do I have too much vacume going to the booster ? I am at a stand still & would appreciate any advice.
-Big Bad Boonze
 
That is not a function of air in lines. and I doubt there is too much vacuum going to booster.

is there a chance that the boost pressure is getting into the booster some how...

did you try running it without the check valve and seeing what happens...
 
yepper

Well I pulled the vacume hose off of the boosters one way valve while the car was running & it had enough vacume to stick the hose to my thumb, pulled the one way valve out of the booster & was only able to blow one way through it. With the car completely off the pedal feels somewhat normal & is quite tall. I thought I had too much vacume because as soon as the car started the pedal was sucked 2" to the floor & when I turned the car (and vacume) off the pedal (on it's own) would return the 2" with a little wooshing sound.
 
Last edited:
Sounds like a bad booster to me.

Worst case - use it for core and get a reman / new from AutoZone, Rockauto, Advance Auto, O'Reilly's, whatever's local to you.

RwP

Edit: If you block the vacuum line and leave the booster installed, but with no vacuum to it, do you have brakes (hard though they may be)?
 
Ralph's got the right idea, here. If when without boost the brakes perform as expected, you're almost certainly looking at a bad brake booster.
 
Back
Top