I have an o4 Expedition. With all regular driving my brakes act completely normal, the pedal is hard, the brakes work great. If I quickly slam the pedal to the floor the pedal will fall to the floor. It pumps back up and then acts completely normal until I slam on the brakes quickly. Hard braking is no problem, just when I hit them quickly.

When bleeding the brakes I had a hard time getting anything from the driver side rear. The first couple attempts the pedal wouldn't go down even with the breather open completely. I finally got some air to come out and then a couple streams of pure fluid. The other brakes bled fine.

After test driving I had the same problem. I re-bled the brakes and had the same issue with nothing coming out at first, then finally some air and fluid.

There is no evidence of any leaks, the level stays the same in the master cylinder.

I appreciate any advice.

 

First I would suspect your master cylinder is on it's way out because the rubber cups are probably worn to the point where they can't flex fast enough with a quick brake application.
Second- vehicles with antilock brakes generally require that you use a scan tool to energize the anti-lock solenoids in order to open the line for complete brake bleeding.

 

Look underneath the master cly. on the booster. Is it wet (master. cly. will sometimes leak like this). However, if the pedal is 'hard', i assume you might mean you have pedal, but then pumps down. Yep, that sounds like a classic master. cly. problem. And by the way, even with ABS, if you have a pressure bleeder, you can get away with not doing a service bleed. Also; you mentioned the calipers. Are they working and not frozen, leaking, or adjusting? Just food for thought.

 

As best I can tell without taking the wheels off the pads on both sides of the back are wearing evenly. Without a pressure bleeder can I get by with old fashioned bleeding or will I need to bring it in? If I do pressure bleed is there a max or minimum pressure? Should I still bench bleed the Master cylinder. As far as I can tell there aren't any leaks, I don't seem to be losing fluid. Would you guess then that the bleeder that was hard to bleed is a separate issue then, maybe some debris from the master cylinder? I took it all the way out and it still took some pushing to finally get fluid out.

 

First- We always bench bleed any Master cylinder before installing it.
Second--- You should have a pressure bleeder to use when bleeding the system, and they generally use around 30 psi to compress the bladder.
You might have to run the vehicle to get the ABS valves to open so the air can get out to the bleeder fitting.
Without the proper equipment it might be best to have someone who has the equip. do the job.
Depending on how you make out after replacing the Master cyl will determine what you need to do.

 

Oh yes, you absolutely HAVE to bench bleed the master before installation, then will have to bleed the entire system. And yes, the one wheel bleeding problem could have been caused by dirt (or anything else) that got packed in there. If the bleeder is able to turn and take out, take it out and clean it. You'll get air in the system, but as you have to bleed it anyway, now's the time. I would really recommend a pressure bleed as it prevents a lot of problems with having to do a service bleed on the ABS.

 

First, thanks for all your help.

I'll look into a pressure bleeder but can I get around it with bleeding with the truck running? I'm going to do some more bleeding to make sure there's no problem with the rubber brake line and caliper, then if all isn't well I'll attack the master cylinder. I wont get to it for a couple days at least, but again, thanks for the help.