Clueless Brake Issue
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Joined: Apr 2016
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From: San Antonio
Clueless Brake Issue
2001 EX with 7.3
Brake issue. Changes calipers, torqued everything to spec. No leaks. Bleed the brakes, pedal still goes to the floor. Bleed them again. Air? Odd since the previous round I bled to the point of only fluid. Pedal still doesn't come back. Another round of bleeding. Same issue. Many more rounds and still the same issue. Mechanic at the garage says "Bad Master Cylinder". (Btw, I'm on a military base in Italy using the MWR garage). Okay, lets get one. Bench Bleed the Master Cylinder, install and same issues. head scratch. No idea. Everything is torqued to spec. Nothing's leaking. If nothing leaks, then how is air still in the system? (please don't recommend another few rounds of bleeding the wheels. If you knew how many rounds I've gone through and quarts of Brake Fluid, you'd see the definition of madness).
Any constructive ideas are welcome and appreciated. Thanks
I can't catch a Brake (pun intended)
Brake issue. Changes calipers, torqued everything to spec. No leaks. Bleed the brakes, pedal still goes to the floor. Bleed them again. Air? Odd since the previous round I bled to the point of only fluid. Pedal still doesn't come back. Another round of bleeding. Same issue. Many more rounds and still the same issue. Mechanic at the garage says "Bad Master Cylinder". (Btw, I'm on a military base in Italy using the MWR garage). Okay, lets get one. Bench Bleed the Master Cylinder, install and same issues. head scratch. No idea. Everything is torqued to spec. Nothing's leaking. If nothing leaks, then how is air still in the system? (please don't recommend another few rounds of bleeding the wheels. If you knew how many rounds I've gone through and quarts of Brake Fluid, you'd see the definition of madness).
Any constructive ideas are welcome and appreciated. Thanks
I can't catch a Brake (pun intended)
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Could this be a situation where the ABS unit got some air in it? If so it needs to be "opened" via computer to allow for proper braking and bleeding.
Unfortunately I am far from an expert on this, but am just throwing it out as a possibility since you just replaced the calipers.
Unfortunately I am far from an expert on this, but am just throwing it out as a possibility since you just replaced the calipers.
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I had considered this and though possible, I believe it’s improbable. When I go back to the garage, I’m going to bring my computer and autoenginuity (not sure if this has the feature) and see if I can check that part.
it still wouldn’t explain why air is still in the system after we bleeding though.
it still wouldn’t explain why air is still in the system after we bleeding though.
Tuned
Joined: Jul 2005
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I've found my mighty-vac hose to leak air at the bleed valve, so I now use a zip-tie on it. Also, sometimes the threads of the bleed valve will leak air on the wheel cylinder or caliper, so I now install new valves with thread tape whenever I do a brake job or bleed. Have experienced both of these situations with dirt bikes & snowmobiles, clutch master cylinders, all of my daily drivers, and the wheel cylinders of 2 classic cars.
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From: Media PA
I had considered this and though possible, I believe it’s improbable. When I go back to the garage, I’m going to bring my computer and autoenginuity (not sure if this has the feature) and see if I can check that part.
it still wouldn’t explain why air is still in the system after we bleeding though.
it still wouldn’t explain why air is still in the system after we bleeding though.
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No Sir, I wouldn't think so. All hoses are Stainless Steel Braided for a 8" lift and less than 2 years old
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Veteran/Sheepdog
Joined: Feb 2012
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From: Western AR
Check the hydro-boost unit, but if it was working fine before the caliper change...
There is a test function on my NGS tester (Ford software) that allows me to purge my ABS module by cycling the pump and pushing fluid through it. I have used it successfully to fix a "soft pedal" on my '04 Expedition.
There is a test function on my NGS tester (Ford software) that allows me to purge my ABS module by cycling the pump and pushing fluid through it. I have used it successfully to fix a "soft pedal" on my '04 Expedition.
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If you let the master cylinder reservoir drain of brake fluid there is a good chance of getting air into the ABS controller, and depending on the situation it can have enough air to use up all the displacement during full pedal stroke. And without using software to follow the service procedure of activating the valves and pump it is extremely hard to purge all the air out. Sometimes if there is a small amount of pedal response you can spend a day using the conventional bleeding procedure and mass quantities of brake fluid by making 35mph stops on a loose surface to activate ABS between rebleeding, but it’s not fun. We had to do that after installing prototype ABS systems with no scanner software available.
Without letting the reservoir drain of brake fluid when many people change out calipers and go through the bleeding procedure the brake pedal gets pushed longer then normal travel. Unfortunately with a system where the brake fluid has water absorption and anti-corrosion inhibitors have depleted over time corrosion forms in the back areas of the master cylinder bores. So travel into this area nicks the master cylinder cups on one or both circuits causing loss of pressure integrity and long travel. A master cylinder change out is the only solution. A booster failure would result in a short and hard to apply brake situation.
I often tell people to replace masters with Motorcraft cylinders. There have been too many times other aftermarket master cylinders have failed during install, and I’m not sure if it’s just a quality issue, or as built it’s poor initial lubrication that hurts the new seals, but it happens too often.
Without letting the reservoir drain of brake fluid when many people change out calipers and go through the bleeding procedure the brake pedal gets pushed longer then normal travel. Unfortunately with a system where the brake fluid has water absorption and anti-corrosion inhibitors have depleted over time corrosion forms in the back areas of the master cylinder bores. So travel into this area nicks the master cylinder cups on one or both circuits causing loss of pressure integrity and long travel. A master cylinder change out is the only solution. A booster failure would result in a short and hard to apply brake situation.
I often tell people to replace masters with Motorcraft cylinders. There have been too many times other aftermarket master cylinders have failed during install, and I’m not sure if it’s just a quality issue, or as built it’s poor initial lubrication that hurts the new seals, but it happens too often.
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Stewart
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From: San Antonio
So I'm an Idiot. I was attempting to swap brake systems which didn't work out so I went back to the old system. When I installed it, they were reversed. L on R and R on L. They fit right? so whats the big deal? Brake Bleed valves that are pointing down are a no-go. Pulled them off, swapped them over, bled the system and instant pedal. This was caused by not paying attention and I guess it happens to us all sometime or another. This was a good learning point for me though because next time I have an issue, I'm gonna sit back and just look at what I've done to see if I'm not missing something. Please pass today's bonehead award to me 
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Thanks guys. Nothing like a little dose of humility to bring you back to earth. I’m thick skinned and have a good sense of humor about it. I’m sure this will make for some cannon fodder for months to come, lol.
