Another Hydroboost question

[Bronkster]

I finally fired up the Bronco after many upgrades and a year of being apart. The hydoboost is all plumbed in and I cycled the steering countless times and have that full. I tried to bleed the brakes and can't get any fluid moving. I cracked the lines at the master cylinder because I completely removed the bleeder from the passenger rear and could get no fluid and finally removed the cap from the master cylinder and had someone apply the brakes and...nothing. I have the angle bracket and fulcrum from ebay and I lengthened the rod from the pedal as far as I could. I remember reading where a guy had the rod missing from the hydroboost and had similar problems, but I checked that. It seems like there is plenty of throw to make it work, in other words the rod on the input side of the hydroboost moves quite a bit, but still nothing. The pedal has about 4" of travel and seems to bind a little at the very bottom and you have to pull on it to get it to go back to the top. Where should I start?

 

[Pedestrian]

"I lengthened the rod from the pedal as far as I could"

Try readjusting your pedal freeplay.
You need about a 1/4 inch of play in the pedal. If the rod is extended too far, the mastercylinder piston will not return far enough to pick up fluid from the reservoir.

 

[Pedestrian]

Also, you can bleed the brakes without the motor running, makes it much easier.

 

[Bronkster]

I'll try making sure the master cylinder piston is returned all the way and shorten the pedal rod for a little freeplay. I tried bleeding with the engine running and not running, but if it's working shouldn't I be able to crack the line at the master cylinder while someone applies the brakes and get fluid?

 

[ransil]

Did you bench bleed the master cylinder?


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[TOFIC]

start with the master cylinder!!
assuming you have the HB hooked up right this is the first place to start
Bench bleed the SOB again, make sure you see fluid movement in the reservoirs before you go on. this is critical so do not continue until you are 100 and 10 percent confident the MC is working.
after this, mount the MC and connect the brake lines
do NOT connect any rods or other parts just the lines!!
open the bleed valves and see if you get fluid flow out of the wheel cylinders.
if you do not find out why and correct the problem.
using a rod (screwdriver works) push the MC actuating piston and have some one listen for the brake pistons to work.
if this works, bleed the brake system using the screwdriver until most of the air is out.
connect MC to HB but NOT to the brake pedal
watch the rod out of the back of the HB, movement should be minimal.
if this works, do the HB bleed sequence, then do it again!!
make sure this is working correctly,you should be able to push the rod into the HB and see the brakes work (watch the front calipers, you have discs right?)
make sure everything works, before you continue.
put the rod on the brake makes sure there is some slack (25 thou is the norm)
bleed both systems again!!!
that should do it
TOFIC

 

[Bronkster]

I did not bench bleed the master cylinder, but will do that. Pedestrian was correct with the piston not completely returning. I had to put spacers between the hydroboost and the angle bracket to allow that to happen. Replaced both rear bleeders and still no fluid. Great flow at the front calipers. I can crack the line at the master cylinder for the rears and have fluid there. I'll bench bleed so I can watch what's going on and then work my way back to see how far fluid is traveling and why it's not making it to the rear wheel cylinders. Thanks for the help!