I’m at a loss with brake issues…

Joined
Jun 5, 2016
Messages
518
Location
California
I’m at a loss and looking for some advice from people that have experienced what I’m experiencing. I had this issue even prior to changing everything that I’m going to list below:

Vehicle: 2002 F-150 220k miles

Replaced: Brake master cylinder (Motorcraft), all 4 calipers with new Element 3’s, new Motorcraft blue brake pads, all rubber brake lines replaced (Motorcraft) and front lines replaced with SS lines.

I bench bled the MC, installed on the truck, then bled at the MC lines with my Motive bleeder.

Connected my Autel scanner and cycled/bled the ABS pump twice before moving on to each caliper (staring from furthest from the booster). Then did a brake bed-in procedure (Zeckhausen).

Got all of the bubbles out and even used a rubber mallet to tap on each caliper to get any and every bubble out. My problem is that when I press on the brake pedal with the engine running, the pedal makes a “whoosh” sound and travels “softly” about 1 1/2” before getting firm. Sometimes if I drive for too long and try to come to a stop, I experience brake fade and it’s hard to stop. Am I bleeding the ABS correctly? Am I supposed to bleed the ABS per caliper?

I’ve read that this could be a bad ABS pump, a bad booster (split in the diagram), or still have air in the lines.

I’m at a **** loss..
 
The sound is normal since the booster is pneumatic. When you press the pedal down, air is admitted from the cabin area (pedal side). Is the push rod from the booster to the MC adjustable? You may be able to get some of the play out by making it longer.

Sometimes if I drive for too long and try to come to a stop, I experience brake fade and it’s hard to stop.
I'm not sure what you mean there. Brake fade results from overheating. Do the brakes heat up when you're driving without using them?
 
The sound is normal since the booster is pneumatic. When you press the pedal down, air is admitted from the cabin area (pedal side). Is the push rod from the booster to the MC adjustable? You may be able to get some of the play out by making it longer.


I'm not sure what you mean there. Brake fade results from overheating. Do the brakes heat up when you're driving without using them?
I bought the booster rod adjustment tool from CSSB and have .20 thou air gap between the MC piston and booster rod. I’ve heard that sometimes new pads can gas off and cause brake fade. But yes it’s not really heating up but I can smell the pad material. Could it just be newer pads that are causing this?
 
Last edited:
I've had several vehicles not want to stop 'til the frictions were bedded in & cooled. Brake Boosters generally have a diffuser to quiet noise. The Booster should hold a vacuum.
I just don’t get why after bleeding everything, my pedal is spongy for the first 1 1/2” and the gets firm
 
Does the Booster hold Vacuum? Shortly after shutdown....Try removing the Booster Check Valve....If no vacuum is stored in the Booster, Either the Booster diaphragm is busted OR vacuum is leaking at the master cylinder mount
 
Engine off .................... is the pedal nice and solid hard with a very short travel then?
Yes with the engine off the pedal gets solid after about 3-4 pumps. If I hold onto the pedal while it’s hard and start the engine the pedal goes down slightly
 
Does the Booster hold Vacuum? Shortly after shutdown....Try removing the Booster Check Valve....If no vacuum is stored in the Booster, Either the Booster diaphragm is busted OR vacuum is leaking at the master cylinder mount
I’ll have to try that thank you
 
Yes with the engine off the pedal gets solid after about 3-4 pumps. If I hold onto the pedal while it’s hard and start the engine the pedal goes down slightly
I'd say booster vacuum is probably not the issue then.

Vacuum pump on the engine (diesel) ................. vacuum gauge on its output - start the engine and see the response from gauge - should get pulled down promptly and then stay there ............

If you now press the brake pedal what happens to the vacuum reading?

Booster you installed - 100% sure its the correct thing? .............. possibly a dual stage that can supply a lot more than a single stage boost? (often responsible for diesel brake pedal creep on diesels)
 
I'd say booster vacuum is probably not the issue then.

Vacuum pump on the engine (diesel) ................. vacuum gauge on its output - start the engine and see the response from gauge - should get pulled down promptly and then stay there ............

If you now press the brake pedal what happens to the vacuum reading?

Booster you installed - 100% sure its the correct thing? .............. possibly a dual stage that can supply a lot more than a single stage boost? (often responsible for diesel brake pedal creep on diesels)
My truck is an F150 so it’s gas. Changed out everything besides the brake booster. Pedal travel is long and grabs halfway down..
 
Yes with the engine off the pedal gets solid after about 3-4 pumps. If I hold onto the pedal while it’s hard and start the engine the pedal goes down slightly
Erm this is a nono - should be solid imediately.

Try again:

pump pedal with engine off till nice and solid with engine off ..............

go have a beer

come back and pedal should still be solid on FIRST pump with engine off - yes?
 
Erm this is a nono - should be solid imediately.

Try again:

pump pedal with engine off till nice and solid with engine off ..............

go have a beer

come back and pedal should still be solid on FIRST pump with engine off - yes?
I’ll have to try this tomorrow morning and report back!
 
You stated you get 3-4 power assisted pumps, there is nothing wrong with your booster or check valve. A swoosh sound when applying the brakes is normal. Leaky boosters will hiss all the time the engine is running. I would rebleed the brakes again with your scan tool.
 
Last edited:
I'm willing to bet that something is up with the ABS pump if you replaced all those parts and have the exact same issue. Have you regularly replaced your brake fluid on this truck?

I would try this test. Get the truck up in the air safely at all 4 corners. Have another person press down the brake pedal or wedge a board between the seat and brake pedal. Go out to the truck and try to spin all 4 tires. They should be locked at all 4 corners. If they aren't you may have an ABS valve that is sticking.

As for the brake booster, does the brake pedal firm up when the truck is off?
 
I'm willing to bet that something is up with the ABS pump if you replaced all those parts and have the exact same issue. Have you regularly replaced your brake fluid on this truck?

I would try this test. Get the truck up in the air safely at all 4 corners. Have another person press down the brake pedal or wedge a board between the seat and brake pedal. Go out to the truck and try to spin all 4 tires. They should be locked at all 4 corners. If they aren't you may have an ABS valve that is sticking.

As for the brake booster, does the brake pedal firm up when the truck is off?
I’m going to try this because I didn’t know about this trick. I’ve heard that these trucks are known for having bad ABS pumps as they get older as well
 
Back
Top