I got my crap together recently and started working on installing my new big brake kit. The front rotors and calipers were a very simple swap, no leaks (so far ) but I'm having a bit of a problem.

After the swap the pedal is mushy, and if I hold it down, the power steering pump cries out in pain because it can't keep up the vacuum. It's almost like I have a vacuum leak somewhere, but I have made no changes in that area. The brakes have been bled thoroughly, and I can't get any more air to come out, yet the pedal is still soft and it otherwise acts like theres an excess of air in the system. I have not taken it for a drive yet, I want to try to resolve this problem before I need to depend on the brakes to stop.

I did disconnect the brake line but I did it at the caliper, the old factory line was a perfect fit on the new calipers. I got everything else ready and the last thing I did was disconnect the brake line and right away connected it to the new caliper so I can't imagine there being too much air left in the system.

Am I forgetting something else? I remember reading about a problem like this before but I don't remember the solution.

By the way, the larger rotors and red calipers look BEAUTIFUL in my opinion. There's about a 1/4 inch clearance from the caliper to the side of the wheel (less than that between the lettering on the caliper and the spokes of the wheel), but it looks awesome. Here's a picture.

http://putfile.com/pic.php?pic=1/2920422098.jpg&s=x2
http://putfile.com/pic.php?pic=1/2920435252.jpg&s=x2
http://putfile.com/pic.php?pic=1/2920450750.jpg&s=x2

The pictures don't really do it justice. Next time the sun shines I'll get some more pictures.

[IMG]local://upfiles/20167/4BDB98162AAA4DC18D0034BFF656A021.jpg[/IMG]

 

Ther is no doubt in my mind you have air trapped somewhere in the system.Try pressure bleeding from the caliper toward the master cylinder.You can bang around the brake system with a hammer to try and dislodge the air bubbles.

 

make sure its a sledge hammer... better yet, a jackhammer.

 

the front calipers came with air in them. make sure when u bleed them that you start with the caliper farthest away, then closer until u get to the closest. and i have no freakin clue why ur power steering pump would cry out if you did brake work. it is completely unrelated. double check all of the fittings for tightness as well

 

No, it is related. The power steering pump provides the vacuum for the brake booster on the 4.6 engines.

I put the right front rotor/caliper on first, and bled it right away without starting the car, just to get the majority of the air out. I then swapped the front left side, and bled it, too. Here is where the pedal started to feel funny. With only one new caliper on, it felt normal. Anyway, I then started the car and bled the front right, till no more air came out (two bleeds), then did the front left (this one took 5-6 bleeds). The pedal still felt soft so I checked the front right again, and no air came out with two more bleeds. Checked the front left again with two bleeds and no air came out.

I took it out for a cruise today, and got up to the speedlimit on my road (55) and slammed on the brakes as hard as I could without locking them up, and there is a definite increase in braking power over the stock brakes at higher speeds. With how far the nose dipped down, they are definitely clamping very hard. The pedal has a slightly larger soft zone than it did before, and it feels like it comes up a little slower but otherwise it feels alright and there is plenty of power there. I'll bleed them again after I go for a cruise tomorrow again and see if I get any more air out.

The kit came with new brake lines, but I did not swap them because they were the exact same hose. All of the rest of the factory hardware was re-used and no leaks. I just hope the softness in the beginning of the travel of the brake pedal will go away after I swap out the rears, too.

Snapped another quick picture while I was out.

[IMG]local://upfiles/20167/4B321C9CC2F74EA6906C55E28E250C74.jpg[/IMG]

 

hmmm, weird. i guess you learn something every day

 

how much oversize have you gone with the new 'big brake' kit? the reason for the 'mushyness' or further peddle travel your feeling is most likely due to the need for a larger master cylinder

 

If your gonna wait to do the rear brake's I would bleed them also I bet you will get your stiffer pedal back. Start with the passenger rear. Or like you said you will get it back when you do the swap.

 

I am with ninja sounds like the master bore cly. is to small I have had this problem with 87-93 change over to 4 wheel disc

 

Thanks for the help all.

The oversize is the same size that is on the cobras. 13" in front, 11.5"(? somewhere around there) in the rear. The calipers are two piston calipers straight from FRPP for the Cobra, and the rotors are just off-brand slotted and drilled rotors, still 13" in diameter. Did the Cobras have a different master cylinder?