Brakes
 

When I push hard on my 08 FEH's brake pedal, I can feel it bottom out on the floorboard. At least that is what it feels like. The behavior is the same with the ignition on, or off. Is this normal?

Re: Brakes
 

No, this is not normal! It sounds like your brake module needs reprogramming or you may need a master cylinder replaced. It also sounds like what my brake pedal did after my brake ABS module was reprogrammed. Your required to do a brake pedal calibration by pressing on the pedal in "Park" as far as it will go. The Ford tech forgot that calibration requirement after the reprogramming and almost drove my FEH into a wall.

It could also be a fault in your PCM not calibrating your brake pedal. Go to the dealership as soon as possible.

GaryG

Re: Brakes
 

OK, I'll do that. Do you know if the system is fully hydraulic when the power fails? Like on non FEH's When other cars do this, it is a sign something is wrong with the hydraulics.

Re: Brakes
 

The brakes are power assist like normal brakes but the assist is electrical instead of vacuum. The intake valves stay open longer in our Atkinson cycle engine and doesn't create enough vacuum for the brakes and they wouldn't work during EV anyway.

If you lose electric assist, you still have hydraulics but it's hard to stop. If you can still stop, the hydraulics are still working. Since you are not getting any warning lights, I suspect the PCM is involved, although I would not rule out a bad master cylinder either. Test your brakes until you get it to the shop, and remember you have "L" to slow you down and a parking brake to help you stop. Just hold the parking brake release while using the foot parking brake pedal you have on your '08 if you lose hydraulics. If you don't feel good about driving it, call Ford roadside assistance to get it towed.

GaryG

Re: Brakes
 

The brakes seem to stop the car, even in an emergency stop. My experience is with the vacuum assist brakes. When the engine is off, you still have hydraulic brakes, and you cannot push hard and get the pedal against the floor. If you do, and the brakes are adjusted, it usually means a hydraulic problem.

I do have to really push on the pedal to get it to the stop, but I think it should never get there!

I'll takt it to the dealer today. If they have another hybrid on the lot, I will see if it's brake pedal has the same feel

Re: Brakes
 

BTW, I believe "regen" only affects the front brakes. The rear brakes are always active.

Re: Brakes
 

Well... regen affects all four wheels in the sense that it doesn't regen at the wheels. The motor drags on the end of the drive shaft acting as a generator... where that "negative" power would go is up to the differential, isn't it? so in effect if you have an AWD model, does't regen affect all four wheels? On the FWD model that wouldn't be true of course.... anyone know the answer to that?

I'm pretty sure its not true that the back ones are "always active"... but to be honest thats only a conclusion drawn from my memory of previous posts. Others that have the repair and service manuals would have a more definitive answer.

Re: Brakes
 

I don't think that the rear wheels, even on AWD models, provide any energy to the generator. Mostly because the hybrid part of the drive system, is the same between the FWD and AWD models. Plus, during braking, I don't think the AWD system, which does its "200 times a second" thing, is ever engaged.

From what I read here and on Yahoo, the rear brakes always being active, is the last "fail safe" in the braking system. If the regen system fails, and fails in a way that prevents all front braking, the rear brakes will eventually stop the vehicle.

Re: Brakes
 

Here is what the manual says guys:

"Since the regenerative braking uses the electric motor to slow the vehicle's front wheels, front brake pad wear is reduced. The rear brake pads, because of the regenerative braking, wear at approximately twice the rate of the front brake pads."

GaryG

Re: Brakes
 

So, does the fact that the rear wear at twice the rate support my thought that the rears are always in use (when braking)?

Re: Brakes
 

It certainly seems to at least imply that.... the USUAL wear pattern on a vehicle is actually the reverse of this... the front brakes usually wear much faster than the rears.

Re: Brakes
 

Yes so what they are saying is you will replace the rear brakes first, most likely at or near 80,000 mi. And maybe the fronts at 140,000 mi. One of the undisccused benifits of a hybrid

Re: Brakes
 

Using "L" like I do may increase the life of the rear brakes pads and rotor much beyond 80,000 miles. Walt ask were the rear brakes always in use and most likely some rear brakes are used, but remember the hole idea is to save as much energy as possible. My habit is to use "L" to slow the vehicle before relying on the computer to use the rear pads. The hypermilers call it DWB (driving without brake) and you'll save gas in any car trying to use this technique. The rubber on my brake pedal looks new at 40,000 miles and I hope it will look new at 100,000 miles.

Back to Walt's question, it all depends on how much brake force you request at the pedal and conditions for regen. If the SOC is high, the battery or traction motor is hot or the outside temperature is below 50F, your going to have more use of the pads and less regen. In ideal conditions, you can almost get ~80-90% regen in "L" at throttle back and 100% with a little more brake pedal pressure. This slows the vehicle down pretty fast in the '05 model.

GaryG

Re: Brakes
 

From what you've posted though Gary it appears that when regen is applied the force developed is only applied through the front wheels even in the AWD model... true? I'm really curious as to what kind of control/differential they have to send power to the back wheels during drive mode. Its not electric only... we know that. If it were a normal differenetial, then this whole 200times per second would be a load of crap because there isn't any smarts in it making decisions.... so I'm curious as to what kind of transfer mechanism there is.... is there any info in those manuals of yours?

Curiousity of an AWD owner.

Re: Brakes
 

Its the same front/rear transfer case that is used in the gas-only models, no?

AWD system makes use of the ABS system's smarts. When the front wheels spin faster under acceleration than the rear, it engages the transfer case to send power to the rear wheels. That power comes from what ever is providing power (electric, gas, both) to the front wheels.

Now, while the sensor can measure slip 200 times per second, I doubt the transfer case can be engaged/disengaged/reengaged that fast.

Re: Brakes
 

Is there some sort of clutch in there then?

Re: Brakes
 

Okay Guys, I'll just quote the manual and stay away from clutches and engagements. We all know the history on that subject.

Rear Drive Axle and Differential:

"The rear axle drive pinion receives power from the engine through the transaxle, transfer case, driveshaft, and active torque coupling, and is always engaged."

"When it is necessary for one wheel and halfshaft to rotate faster than the other, the faster turning differential side gear causes the differential pinion gears to roll on the slower turning differential side gear. This allows differential action between the two halfshafts." Section 205-02-1

GaryG

Re: Brakes
 

Good point... I certainly wasn't trying to start that other "discussion" again. :angel:

Re: Brakes
 

Hello!

Could you, please, help me in my problem.

I'm owner of the o8'Ford Escape Hybrid.
During the Brake Fluid Replacement without Power Bleeder, I've encountered the following problem:

According to manual, scan tool was connected and corresponding service routine "Brake Fluid replacement without power bleeder" was selected.

For first 3of 4 bleeder screws following instructions screens were provided:

1) Attach fluid container, open the bleeder screw, press tick to continue.
2) Fully press and release the brake pedal 10 times, press tick to abort.

During the each press\release step system increased counter from 0 to 10.
After the 10th step it provided instruction to close the current bleeder screw and proceed to the next.

On the last (left front) bleeder screw system proposed to
"Fully press and release the brake pedal 30 times"

But after the 10th press\release counter stopped.
Each following pedal press from 11 to 30 didn't increase the counter. Also brake pedal vibrated during the each press from 11 to 30 (like ABS).
Even after 30 presses, scan tool didn't provide any new information.
It seems it hung after 10 steps.

After that System cannot complete initialization with Error C1525.

I've tried to do this again 4 times - each time system proposed to do 30 presses for the last screw and stopped on the 10th press.

Now, my Escape hybrid has no brakes. I live in Eastern Europe, there is no special support for USA cars near me.

If you earned this problem, or know how to resolve it - please, help me.

Best regards.
Andrey from Ukraine.