Spongy brakes, have tried most everything.

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May 29, 2005
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Location
Ozark Mountains
2012 Mazda 5 with 156,000 miles. It is the sort of tiny mini van with a 2.5 L 4 cyl. and an automatic. It is in good condition otherwise.

The brake pedal goes almost to the floor but then seems to stop normally. Then if reapplied quickly the pedal has slightly more pressure resistance when pushing on it but not much. Use the brakes again and then the same thing.

Changed the master cylinder twice just in case I got a bad new one. All the short flexible brake lines are new. Complete rear new brakes including new calipers.

Three different people have bled the brakes including a good shop.

Please help. Thanks. I am getting desperate.
 
2012 Mazda 5 with 156,000 miles. It is the sort of tiny mini van with a 2.5 L 4 cyl. and an automatic. It is in good condition otherwise.

The brake pedal goes almost to the floor but then seems to stop normally. Then if reapplied quickly the pedal has slightly more pressure resistance when pushing on it but not much. Use the brakes again and then the same thing.

Changed the master cylinder twice just in case I got a bad new one. All the short flexible brake lines are new. Complete rear new brakes including new calipers.

Three different people have bled the brakes including a good shop.

Please help. Thanks. I am getting desperate.
Next on the list is the booster !
 
An independent shop tried to bleed the ABS controller, but they could not connect with either unit they had. A scan tool?

Then the head tech. at Mazda said Mazda does not support the software to bleed the ABS for that year and model anymore. He said it should bleed itself during a normal brake bleed though. ??

I was also told by the Mazda tec. that the brakes would get harder to use if the booster was bad. ??
 
An independent shop tried to bleed the ABS controller, but they could not connect with either unit they had. A scan tool?

Then the head tech. at Mazda said Mazda does not support the software to bleed the ABS for that year and model anymore. He said it should bleed itself during a normal brake bleed though. ??

I was also told by the Mazda tec. that the brakes would get harder to use if the booster was bad. ??

It might bleed itself if you activate the ABS function. It won't ever if you just drive. You could try that on some grass or any slippery surface where there's nothing to hit.
 
Sounds like HCU failure. fairly common on that generation fords.
 
Had similar symptoms once on a mitsubishi, where it was the HCU but hundreds where it wasn't.

the mitsubishi was a lot like a volvo s/v40 so maybe there's a link to ford aswell. Can't remember what brand GCU it was. Denso or Bosch seems most likely.
 
Back when I was a kid during the Jurassic period spongy brakes meant you mostly needed a new master cylinder.

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Then the head tech. at Mazda said Mazda does not support the software to bleed the ABS for that year and model anymore. He said it should bleed itself during a normal brake bleed though. ??
??? Sounds quite bogus to me, more like, I don't feel like spending lots of time on a low paying job where I might spend more time doing diagnostics than replacing parts.

Sounds like air in the line to me. If you can't make the ABS cycle via software, you can make it by doing brakestands in a snowy parking lot.

Complete rear new brakes including new calipers.
Can you do a quick check on the rear calipers, and make sure that the bleeders are physically above the brake lines? Every so often, someone makes a goof and gets left side mixed up with right side. You can tell because the bleeder screw has to be the highest point in the caliper--air rises, and the point is to let the air out. Get it wrong and the brakes will never bleed properly. I'd do this quick check first before going any further.
 
Sounds like HCU failure. fairly common on that generation fords.
I still remember GMT400's with RWAL, The dump valves would hang open & cause a low pedal. No amount of bleeding or service brake parts would fix it.....The HCU had to be replaced or bypassed.

In those days when ABS was a rarity....This drove many mechanics crazy!
 
When the master cylinder was replaced both times, did you bench bleed it first? This needs to happen before you install it in the vehicle.

Sounds like you still have air in the system.

On a vehicle where I could not activate the ABS pump via 2-way scan tool, I would place the vehicle on jack stands, having both drive wheels off the ground. Then lightly clamp a pair of long-nose locking pliers on the rubber brake line on one wheel. Lightly press the brake to engage the the transmission, then accelerate the wheels to about 20-30 MPH. When you press on the brake to slow the wheels, the ABS should activate since the one wheel won't slow down as fast.

This has worked a few times, then bleed the brakes, repeat if necessary.
 
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