2009 CX-9 GT - Poor brake performance

delucat2

Member
:
CX-9
Are the brakes on this thing just terribly poor...or do I have a problem?

I have a new to me 2009 FWD with 20s, 70,000 miles (grandma's car)... and these brakes are absolutely terrible. In the past I replaced her rotors and pads once because she had issues with squeaking (now has Akebono ceramics at all 4 corners), but no other work because of the low miles.

Recently the car became mine and I heard the booster hissing / very hard to push pedal. Diaphragm gone... so as long as I was in there, I replaced the master cylinder. Vacuum bled the fluid (complete change out - 2 quarts), used a scan tool to cycle the ABS...no air in the system.

Now, even when I stand on the brakes, I can barely get the front wheel ABS to activate. The pedal has what I feel is an excessive amount of travel before getting deceleration (was the same before the parts change), and even with hard application, braking seems weak.

Has anyone chased "soft brakes" in these things before? Are the FORD (yes, FoMoCo all over the brakes and 3.7 engine) brakes just undersized with this vehicle and the 20 inch rims? Change to semi-metallic pads?

Racking my brain.

Thanks
Tony
 
:
2010 CX-9 GT
I've never had any complaints about the brakes in the 2010 I own. It sounds like you have unresolved issues. The pedal travel you describe sounds like air in the system.

I've also not been impressed with ceramic pads in comparison to "normal" pads. They need some heat to work and tend not to have the same initial bite. The do produce less dust, but that's the only positive I've noticed.
 
:
Mazda CX-9 Grand Touring 2016
Are the calipers in good condition and moving freely? Are the sliding rods clean with suitable caliper lube on them? Did the rotors have the preservative oil cleaned off before use? Are the pads free to move within the calipers? New brake hardware correctly installed? Jack the car up, remove a wheel, pry the pads away from the disc, have someone step on the brake pedal and watch the pads move to the disc and the parts of the caliper move. Do this for each wheel.

Could the brake booster or master cylinder be new-defective? Is there one or more spongy old brake hoses? The long pedal is indicative of air in the system somewhere.

The Akebono pads should be great. Did you follow a break-in procedure? Try testing the ABS on a gravel road or other surface that doesn't have the grip of clean pavement.
 

delucat2

Member
:
CX-9
I must have air in the system someplace - but the caliper end is good.

To initial bleed - I ran most of a quart of fluid from the MC to all 4 corners using a MitiVac. Solid fluid (using clear lines), using speedibleeder bleeders all 4 corners with teflon tape) at all 4 corners. Manually pumped with speedibleeders / engine off after that. No air in fluid at that point. Not able to get a firm pedal.

I bled the master by disconnecting the 2 output lines and pumping the brakes with plugs in the ports to clear any the air in the master. I then attached the 2 output lines and bled with them cracked. Cracked the 4 output lines from the ABS and bled those (this is a common fix on similar Ford ABS units). Then attached a scan took with an ABS bleed capability and cycled that while bleeding at the calipers pumping the brake. manually bled a bunch more fluid through by pumping brake pedal. Pedal is still soft / long travel.

DRIVING ME NUTS
 
:
2010 CX-9 GT
I must have air in the system someplace - but the caliper end is good.

To initial bleed - I ran most of a quart of fluid from the MC to all 4 corners using a MitiVac. Solid fluid (using clear lines), using speedibleeder bleeders all 4 corners with teflon tape) at all 4 corners. Manually pumped with speedibleeders / engine off after that. No air in fluid at that point. Not able to get a firm pedal.

I bled the master by disconnecting the 2 output lines and pumping the brakes with plugs in the ports to clear any the air in the master. I then attached the 2 output lines and bled with them cracked. Cracked the 4 output lines from the ABS and bled those (this is a common fix on similar Ford ABS units). Then attached a scan took with an ABS bleed capability and cycled that while bleeding at the calipers pumping the brake. manually bled a bunch more fluid through by pumping brake pedal. Pedal is still soft / long travel.

DRIVING ME NUTS

YouTube and the various Ford Edge forums are littered with examples of spongy brake pedals caused by faults in either the ABS unit or the ABS controller. Maybe you can try some of the fixes proposed for the Edge? It sounds like some scan tools don't cycle the ABS pump properly, are you sure yours is doing the right thing?

Some people had luck with forcing the ABS to actuate by stomping the brakes on a dirt road, which can free a stocking valve inside the ABS unit. Others resorted to buying new ABS parts and swapping them in.

Good luck.
 

delucat2

Member
:
CX-9
YouTube and the various Ford Edge forums are littered with examples of spongy brake pedals caused by faults in either the ABS unit or the ABS controller. Maybe you can try some of the fixes proposed for the Edge? It sounds like some scan tools don't cycle the ABS pump properly, are you sure yours is doing the right thing?

Some people had luck with forcing the ABS to actuate by stomping the brakes on a dirt road, which can free a stocking valve inside the ABS unit. Others resorted to buying new ABS parts and swapping them in


I'm going to the dirt road this morning.
 

delucat2

Member
:
CX-9
This is crazy...after a few quick stops...the passenger front caliper is not releasing...dragging badly. I'll need to replace.


Christine
 

delucat2

Member
:
CX-9
Replaced both calipers. Car drove great for a 2 - 3 mile road test.

Drove again this morning. After 2 miles the TCS OFF light on the dash turned on (would not respond to the switch). I felt the brakes start to drag. Disconnected the pos cable and let it sit.

It is the ABS/TCS that is applying the brakes and not releasing.

About 10 minutes later, started and drove normally. Within a mile the brakes are being applied full force. I tried disconnecting the pos cable on the battery. Still full brakes being applied.

Parked waiting for tow to shop now. This is the craziest thing I've ever experienced.

all it can be is the computer/TCS/ABS - something electronic
 

delucat2

Member
:
CX-9
The shop said they'll take it next week. For now, driving with the ABS disconnected 50A fuse pulled.

Brakes act and feel fine, so mechanically, the brakes are good. The front calipers were likely not bad and didn't need to be replaced. The soft pedal could be caused by the TCS sending improper data to the ABS unit, causing the unit to improperly mess with the brake line pressures. He's never seen it. Wants to see if it stored codes.

According to the shop I'm talking to, this is all driven by a TCS malfunction.

Since the only 5 sensors the TCS uses are the steering angle sensor and 4 - wheel ABS sensors, he believes one or more of the ABS sensors has failed and is sending bad data to the computer. He suggested the cheap way to do this would be to replace the 2 front sensors at the hubs since those were the ones locking up. For $50, doing it and keeping the OE parts that come off.

The tab to date - $130 booster (known bad), $140 master cylinder, $180 calipers, $50 sensors.

In the end it may just be the booster, sensors and a good bleed that was needed.
 

delucat2

Member
:
CX-9
Yeah I'm confused too. Cx7 perhaps?

Also, did they try the brake lines? The intermittent problem sounds like it might be faulty worn brake lines acting up.

I am able to isolate the electrical from the mechanical by pulling the ABS fuse and the connector to the ABS unit. Like this, the brakes work fine.

This is an electrical problem, not mechanical. From booster to pads, the mechanical system operates great.

Connect the ABS... and after about half a mile the TCS/ABS puts the brakes into full lock (if any braking is applied, it holds it) and does not let go. The TCS/ABS lights come on.

I have to put a wrench on the bleeder valve (i have speed bleeders on it) and relieve the stored pressure, then I can drive the short ride back to the house.