2011 Soft Brake cause and the fix I almost missed!

[bb56]

Hi all,

 

I thought I would pass along my hard earned lesson when I decided to tackle fixing my squishy, soft brake pedal.  The pedal (engine running or not) was going very low to the floor, and stopping power was not great. The pedal would stop the car, but it would continue to get lower and lower as long as I was pushing it down. I've been fixing cars (and everything else) for a long time and I keep my cars for a very long time, so I've seen plenty of problems and fixes.

 

I went around and bled all 4 wheels, using a quart of new brake fluid. I made sure the pads were at least 1/4" thick or more. Fronts were 1/4, rear were 3/8 inch. The fluid that came out was clear, no bubbles, so no fix.I noticed that the rear brake disks had a bit of light rust but since it just rained, it made sense.

 

I decided to change the master cylinder for lack of a better indication of where the problem was. Although I did the bench bleed on the new one,  by the time I reconnected the brake lines,  I was certain I left air at the fittings connecting to the master cylinder. So I bled the fittings by loosening them and having someone push the brake pedal until no more bubbles and spurts came out. The brake pedal felt the same, so again, no fix. I knew I needed to bleed the brake lines again, but I had to go buy more brake fluid first. 

 

While waiting until morning, I spoke with my neighbor who also has plenty of car repair experience. One thing he mentioned was to check the pads to see if they were stuck and flexing under pressure. So since I needed to start on the right rear brake caliper when bleeding, I gave the pads extra scrutiny.

 

Sure enough, there was at least 1/16" gap between the piston and the inner pad! I exercised the parking brake cable and saw that the piston comes out to close the gap. I had my neighbor push the brake pedal while I watched and the piston come out as expected - but then retracted right back to where it was. So the piston was not frozen. It simply was not adjusting to the pad wear. If I exercised the park brake, it should move out then stay, and each subsequent park brake exercise it should do the same, ratcheting it's way toward the pad.  To be certain, I checked the opposite rear wheel and it was fine - the piston was right up against the pad. 

 

With this evidence, I replaced the caliper for $90 (FoMoCo part from Napa) and it worked. Brakes feel fine now. I am embarrassed that I missed this the first time when checking pad thickness.  It was so obvious after the fact.

 

So the lesson here for those with squishy/soft brakes - check the rear adjusting calipers. They should be touching the brake pads, otherwise all the fluid from the master cylinder push will go toward filling up that volume of the retracted piston, the second pump, if fast enough, will bring up the pedal and improve the stopping power - just like mine. Both rear brakes were not getting the pressure from the brake pedal thus causing slow stopping power.

 

I hope this helps others with soft brakes. My guess is that it might even get missed at the dealer service shop which is why you see others on the forum have so many issues with soft brakes.

 

Lesson learned.

Good luck!

 

[Gadgetjq]

Great post BB!  The most frequently mentioned cause of a soft pedal in the Gen1 Edge is the brake booster.  Now I'm wondering if some owners opted for that fix when the 'real' culprit was a faulty caliper.   Yours is a nice addition to the 'possible reasons' database.

 

Cheers!

[bac2010]

I had soft brakes a few years back and brought it into Ford.  They had a hard time finding and fixing the problem - took 3 days.  They did replace a leaking caliper but I think the overall resolution was removing air in the anti-lock brake system.  Not saying the bad caliper didn't contribute to the problem.  Also had the brake booster replaced under the extended warranty coverage so hopefully good for a while.

[bb56]

Thanks @Gadgetjq. 

I had the brake booster replaced 18 months ago under the warranty but it was obvious what was wrong. The pedal would go down and a whistling noise would start as the brakes lost more and more power.  Just sitting still with my foot on the brake pedal would allow the car to start rolling until I pushed harder on the pedal.

 

@bac2010 - I've seen a lot of folks on the forum tell the "several days at the dealer" story for soft brakes and it is the principle reason I decided to document this. Checking the operation of the self adjusting rear brakes is now one of the first things I plan to do if the brakes get soft again.

 

I'm not big on taking my car to the dealer. I got burnt badly when my wife's Mercury Montego had a bad Instrument Cluster and indicated with a seat belt warning light. I have the service manual and the second step of the troubleshooting procedure pinpoint testing would have pointed to the bad IC. After a week at the dealer, I asked if they ran the pinpoint tests and they said yes. The next day the car was fixed and the manager told me that the pinpoint tests showed them where the trouble was.  I'll never know if the tech I spoke to ever told him and just did the pinpoint tests, or he was embarrassed and fessed up. The dealers are not known for their quick troubleshooting skills - they need billable hours like lawyers so why follow the Ford prescribed steps.

[WWWPerfA_ZN0W]

Excellent info and trackdown.  Thanks for adding your experience to the forum.