Low Brake Pedal Won't Go Away

[jhchevy1]

So 1 week ago I did the brakes on my 08 fusion SE. I did front pads, hardware and had the rotors turned. The rear had new rotors, pads, and hardware. I used the rear caliper tool to spin the pistons back in. The brake lines were never opened during this. I had the master cylinder res. cap off when I compressed the calipers so I had to remove some fluid as I did this. The brakes worked great until my daughter drove the car and hit some potholes on the dirt road by us. Ever since then I have a low brake pedal. The fluid level never goes down and there aren't any leaks.The front brakes are the only thing working at the bottom of the pedal stroke. When I press the brakes while driving I can feel the brakes starting to grab about halfway down then the pressure goes away until the last quarter of the stroke. I bled all the brakes out and tried it again but it did the same thing. It sounded like the master cylinder went bad so I picked up a remaned one from O'Rielly's for $110. I bench bled the new one and installed it then bled out all the lines again and made sure all the new fluid had flushed out the lines. The f-ing thing did the same thing when I test drove it.

 

I had read that sometimes air can get into the abs module so I took the car to a brake and muffler shop that I used to work at to have them bled the abs module with the computers help. They said the lines need bleeding and it would be $30 so I had them do it. After and hour or so they test drove the car and then pulled it back in. The messed with it for a while then came over and told me the master cylinder is bad. I explained the situation and they said the remans are crap and that is what is wrong. They would bleed the lines for free next time.

 

I took off the master cylinder and took it back to the store and got another one. They said it sounds weird to them since the remans don't give problems usually. I put in the new M.C. and bled the lines again but I'll be damned if it didn't do the same damn thing.

 

When I was bench bleeding the new M.C I noticed that more air would seem to enter it somehow when I was working the shaft. The air seemed to come out the front port only.

 

I wonder if maybe my res. bottle for the M.C. might have a sealing problem and if anybody has had this happen before.

[FusionDiffusion]

When you bled the lines were there any air bubbles in them or not?

 

The other things I thought of were:

 

1. The rear brake hoses were somehow damaged while doing brakes and they are allowing air in or are expanding like balloons rather than holding the pressure.

 

2. The brake pads and caliper are not seated properly (force is not being transferred to the rotors effectively).

 

3. The caliper seals were damaged when you pushed the pistons back in and the leak is either very small or in a place where you can't see it.

 

4. There is some other unseen damage somewhere in the system (rock or something hit or damaged a line somewhere under the car).

 

I think you should tell the shop you did your own brakes if you haven't already, and have them take the calipers off and inspect everything.

Edited October 26, 2012 by FusionDiffusion

[jhchevy1]

That's where I'm at now. I rented the rear caliper tool again so I can take it all apart and inspect everything. It seems to be affecting the rear brakes the most so the caliper seal is a good place to start and then brake lines.

[jhchevy1]

I tore everything apart on the brakes and inspected everything. I took it back to the brake shope to bleed it again. The pedal feels better but they now think my abs module is bad. When you hit the brakes there is a weird clicking noise coming from it, like a bad valve inside. She probably blew it up hitting the bump and the brakes at the same time. Crap!!!!!

[Carontoc]

I've got the same problem with my 2007 4 cylinder. The problem has occured 3 times now, each time after hitting a pothole with my front passenger wheel, and resolved itself the first 2. I had two different brake places check it after each of the two previous times and some how the problem was resolved while on the lift but without the technician knowing what happened to fix it. The first time they put new pads on it but I didn't buy their story that slight seperation in the front pads was the cause... Sure enough it came back, but the second time I took it to a different shop and they changed the oil before test driving it to see the problem and when the test drove it, it was gone. Now my wife has hit another pothole and it is back. I've never gotten an ABS light but I'm suspecting it is related to the ABS because the problem only occurs when I hit a pothole (bumps don't do it) on the front Passenger side.

 

it is interesting to see someone else has the pothole instigated issue. I would cross off any issues caused by the pad and rotor change in this case.

Let me know if you figure out what is going on.

Edited January 1, 2013 by Carontoc

[FusionDiffusion]

So were you braking when you hit the pothole?

[Altjira12]

I'm having the EXACT same issue with the exact same model. Randomly my brakes go. There is an odd loud "thunk", the car lurches and the brakes hit the floor. I don't know if it is a coincidence or not but it has happened 4 times and every time I have been turning. My brake light does not come on and once the car is turned off and back on the brakes seem fine (still soft though) When I park I pump the brakes till they don't push down anymore and they will stay that way for days, until the car is turned back on and then they are mushy again. My mechanic is at a loss. I haven't hit anything, no potholes, nothing.

[thefoeyouknow]

Make sure all the caliper slide pins are free and can move with little or no effort. If one gets stuck, the caliper cocks sideways, which make the piston have to travel out further, and you get a long pedal stroke.