Is it possible to have air between master cylinder and caliper?

I've been bleeding the brake system for. A few days now nad still have a mushy pedal. When I crack the bleeder nipple at each caliper, I get nothing but fluid. And the pedal feels pretty good. But after starting the Jeep up, the pedal gets pretty soft. Is it just a different feel with the new PR60 axles and calipers, or could there be air in the line. I have not driven it yet, because I'm still completing the install.

Oh, and yes, I did let the MC get really low one time early on the bleed process. I thought it had more and my helper wasn't paying close attention.

I'm not entirely familiar with the jeep braking system or different brakes on the axels so this is just a general statement... usually the brake lines are routed through an abs unit and can also have long lines and verticals height change. If air gets into the abs system due to a dry reservoir, there may be addition steps to bleed the abs, may or not be a bleeder at the abs. Also if there is a lot of vertical height change sometimes it can be very difficult to push air bubbles down through the lines. A lot of fluid and a power bleeder can be helpful for this and even reverse bleeding can work sometimes.

But again, this a general statement so hopefully someone can chime in on the pr60 brakes if they are normally softer than original.

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Usually if MC runs low enough to get air in it, you have to take it off and bench bleed it first. I would carefully drive the vehicle and see how it is on the road. It is common for new brake parts to create a different pedal feel with the vehicle stationary. If you are happy with how it brakes while driving, then leave it. But if not, take it to dealer, explain what happened, and see if they can pressure bleed it and make sure no air is in the abs hcu.

I bled them myself without draining the master cylinder until there was no air. The pedal feels quite a bit softer, especially in the first bit of throw with the Hardcore 60/60 package. I actually then took it to the dealer and had them bleed it using a computer, and it has about the same feel, softer. It gave me peace of mind while lightening my wallet. Every single employee in the dealership, and every customer was out looking under Beast to check it out while it was on the rack.

I have plenty of braking power, though I haven't actually made a hard emergency stop yet. The pedal feel is quite different than it was with my older stock rear and front Euro Mopar Big brakes. I've gotten used to it with minimal driving. I think if it bothers either me or you, the only solution is a larger master cylinder to get the pedal feel back.

how I bled my ABS -

take everything you need to be able to bleed the brakes on location.

find a good stretch of isolated road where you can get up to at least 50mph and slam on the brakes to kick in the ABS - make sure the ABS does kick in, check the brake fluid level do a quick bleed then repeat.

Don't let the reservoir get low.

I use a Motive Powerbleeder now, keeps the fluid level up and I can do it without a helper.

Im not sure of the process youre using, but you should always starr with the wheel furthest from the mc and work closer. So rr, lr, rf, lf. Air can stay traped if you deviate from that process.

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It sounds like you have air in the ABS module. It also sounds like you just changed to a larger axle with larger brakes. The brakes on 1 ton axles tend to change the feel of the brakes and makes them softer and also requires more pedal travel. If you get to the point you are positive that you have all of the air out of the system I would suggest the mopar master cylinder and booster upgrade from the JK-8. It will return your pedal feel to normal, hell even if you do get all the air out or already do the brakes will never feel like stock again until you upgrade some other items.

I had my abs module bled... I had a soft pedal and I got a little body damage wheeling because I couldn't keep 100% control coming down off a ledge. Brake pedal feels almost stock now


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