Aspire brake swap bleeding/pedal softness issues...

[micah]

i have a 90 festy and swapped over the aspire brakes all around. also swapped in an aspire booster and master cylinder (did not swap in the proportioning valve). and as an fyi, i am using a clear hose and a one-way bleeder valve so i can see if there is any air in the lines and make sure it doesnt go back into the caliper as a i bleed. in addition, im doing this w/ someone pumping while i bleed/open and close the bleeder valve on the caliper. all that to say, i dont see how any air could be getting back in while im doing it.

using the above method, i bled the brakes the first time and they were still spongy/soft. (cant remember if it was off or on the first time i did this). had to wait a few weeks until i had time to do it again and finally had some time over the weekend.

in case it matters, the car was off / not running. went around and did each corner a few times. still felt soft. went around a few more times and after a while the pedal finally started to harden up. thought the problem was fixed. put the car on the ground. started it up and the brake pedal went soft again!!! i have also noticed that the car kind of seems to want to die when i push in the pedal (would this point to a booster issue? but a bad booster wouldnt make the pedal soft would it? wouldnt that point to a bad m/c assuming there is NO air in the lines?).

i have no idea what the problem is and would love any advice you guys may have to offer. and im happy to try bleeding them again if anyone things im doing something wrong. ive worked on a lot of cars (including doing complete brake swaps just like this) and never had this much trouble w/ brakes.

thanks.

[FestYboy]

gravity bleed.... but before that, re-bench bleed the master (can be done in the car)

[freshtiva]

Booster push rod needs adjusted out ??? Just a stab, im no expert !

[mechanicaldj]

is it a new master cylinder?

also what kind of adjustment did you do on the rod between M/C and brake booster?

FYI you did not need the booster from the Aspire, old one would work just as well

[JoDan]

is it a new master cylinder?

also what kind of adjustment did you do on the rod between M/C and brake booster?

FYI you did not need the booster from the Aspire, old one would work just as well

same question, is it a new master cylinder? Because I got one for my car and forgot to bench bleed and found out the hard way:p

[freshtiva]

I looked in both my festiva manual and an aspire manual and the push rod clearance is different between the cars. Looks like the aspire boosters are different from manual to auto as well.

[Mike McKown]

I'd bench bleed the master cylinder to make sure all the air was out of it.

Seems to me if the push rod clearance wasn't right you'd either have the brakes locking up or a low pedal, depending on which way it was off.

[micah]

booster and mc came out of a wrecked aspire that another board member owned. i just slapped it in assuming it was fine b/c he said it was. so no known issues w/ it being mechanically bad.

i had the booster and even though i didnt think i NEEDED it thought i would slap it in as well so everything matched the aspire set up.

now my 2 questions are:
1. what is bench bleeding and how do you do it?
2. what is the specs on the push rod clearance? how different? should i be making some sort of adjustment to compensate? i didnt adjust anything thinking it would already be good to go (based on past experiences w/ similar brake swaps etc)

and as an fyi, i dont have any of the old festy stuff to compare or swap back in so unfortunately, thats not an option here.

thanks to all of you so far for the quick and helpful posts!

[wcbarker]

Make sure the self adjusters are working on the rear
If they are under adjusted it would cause this problem

[micah]

Make sure the self adjusters are working on the rear
If they are under adjusted it would cause this problem

would the e-brake be functioning properly if they werent adjusted properly? asking b/c it is and i didnt want to make start making changes to that if this would be a clue...

[Mike McKown]

1. what is bench bleeding and how do you do it?
2. what is the specs on the push rod clearance? how different? should i be making some sort of adjustment to compensate? i didnt adjust anything thinking it would already be good to go (based on past experiences w/ similar brake swaps etc)

Put the master cylinder in a bench vise. Run lines from the cylinders output ports back into the reservoir and fill it enough to cover the ends of the lines. Stroke the MC piston until air stops blowing into the reservoir's fluid. 6-8 times should do it.

I can't tell you what the clearance of the pedal pushrod should be but I'd guess maybe an 1/8" or so. That would be the slack you can feel on the pedal at the top of the pedal stroke if you move the pedal by hand. All you doing is making sure the pedal pushrod doesn't put any travel on the master cylinder piston with you foot off the brake pedal. If it strokes the MC piston just a very little, the MC piston seal will cover the compensating port in the MC bore and cause the brakes to stay on and not release.

[mechanicaldj]

would the e-brake be functioning properly if they werent adjusted properly? asking b/c it is and i didnt want to make start making changes to that if this would be a clue...

did you put the drums on with a slight drag( when spinning the drum)

were the adjusters free to move?

out of adjusted rear brakes normally cause a low pedal, not a spongy one.

master cylinders can go bad just sitting on a shelf with used fluid in them

[micah]

i will go through the rear brakes tomorrow and see if anything looks odd.

anyone have an idea as to why it eventually bled and felt fine until i started the car? something to do w/ the booster not having vacuum until then...?

thanks again for all of the help!

[FestYboy]

if you're touching hte rear brakes, make sure your e-brake levers are moving properly, they have a tendancy to freeze on the pivot point and cause poor adjustment and e-brake activation.

[micah]

i took the rear brakes apart this weekend to inspect them. plenty of pad, e-brake lever works and moves like normal, and they self adjusted just fine. problem is still persisting.

if the car is off and i pump the brake a few times it hardens up and then goes soft again as soon as i turn the car on (im assuming this is b/c the vacuum pressure is released/equilibrated once the booster gets vacuum).

drove it around the block and also noticed that there is a pulse feeling when the pedal gets to the bottom of its stroke. not a shimmy in the wheel like if the rotors are warped but a pulsing you can feel through the pedal. the movement feels fine in regards to the slack/etc.

any thoughts are welcome? in addition, how do you bench bleed the MC while it is in the car? and what do you use to run the fluid from the ports back into the reservoir? i dont have any extra metal brake lines or anything like that lying around.

thanks again for the help.