Front Brake Bleeding

[NSFIAT]

Hello all - I may be in over my head and am hoping to get some clarification!

I recently replaced the brake booster and master cylinder on an '81 (the booster itself was on it's last legs and needed to go). In bleeding the brakes I'm able to get fluid out of the rear brakes, but not the front. When the brakes are pumped I can see the fluid coming up from where the bleeder screw sits, but a full push of the pedal is never enough to push the fluid out. I have steel braided lines on the rear, but rubber lines on the front (both are just over a year old).

Before getting into this I never knew about adjusting the nut on the booster - could this be the leading cause? If so, what am I looking for in regards to adjustment, etc?

[vandor]

The adjustment nut has nothing to do with this. Make sure the fluid inlet hose from the reservoir to the master cylinder is not kinked and is able to supply fluid to the cylinder.

[narfire]

See if this helps
http://www.international-auto.com/fiat- ... lation.cfm

[NSFIAT]

[NSFIAT]

This is the current set-up - the hose feeding the master cylinder is new as well. Of note is the fluid level in the left side of the reservoir - it's at the 'Min' line, while the fluid in the right side is lower. Does the left side hose feed the front brakes? Apologies if that's a stupid question!

The hose doesn't seem to be kinked, but it is definitely pushed up by the presence of the booster. I took lots of photos before taking the old hose and booster out - everything is identical.

[kilrwail]

Make sure you have two copper crush washers installed on the banjo bolt at the caliper - one above the hose fitting and one below.

[azruss]

you may have air trapped in a portion of the MC. loosen the front brake line connection on the mc just enough for it to leak under pressure and see if you can bleed the mc.

[NSFIAT]

Thanks all - all signs are pointing to trapped air in the master cylinder. Up until last night I didn't know what bench bleeding was so I definitely got ahead of myself. I'm going to recirculate back into the reservoir tonight and go from there!

[131]

When the brakes are pumped I can see the fluid coming up from where the bleeder screw sits, but a full push of the pedal is never enough to push the fluid out.

I'm assuming you're applying pressure to the pedal, cracking the bleed nipple, tighten bleed nipple, release pedal? Repeat?

[DieselSpider]

I use a MightyVac vacuum bleeder myself however once the brake fluid starts flowing they gravity bleed with a pretty good flow with no pumping required.

[garion]

When I did mine, I went with speed bleeders. Makes bleeding a breeze. Open bleeder, get friend to pump until it comes out smooth, close bleeder. No need to open/close repeatedly.

[gchocevar]

My Problem Solved,

I had a 69 124 Spider decades ago and a host of other cars that I never had problems bleeding the brake lines until I rebuilt my 1979 Spider a couple of years ago. I tried all the tricks... lowered this, raised that, primed the master cylinder, checked and rechecked the acorn nut gap. The brakes would still grab very close to the floor. I finally went out and purchased a simple manual hand brake bleeder that has up to 30 Hg(~14 psi) of vacuum in which you only require 5 to 10Hg. Lines are now purged and the brake pedal is real hard. If you can't push the air bubbles out try pulling 'em out.

30 bucks well spent.