[softailrider]

The vehicle has about 23000 miles on it, and this is a fairly recent development. The brake pedal is going down too far when it's applied. Took the car in for service, service manager agreed the pedal is going down too far but he said everything checked out good. It's disconcerting, I'm not happy about it. Anybody have any thoughts?

 

[walker]

Flush out all the old brake fluid with a pressure bleeder?

 

[HyRax]

Yep, flush the lot and start again.

 

[seagrass]

Third vote for replacing brake fluid.

Brake fluid absorbs moisture over time and is recommended to be changed every 3 years or 36,000 miles which means your 2019 vehicle is due or almost due for this maintenance item.

Seagrass

 

[dpgabg]

The vehicle has about 23000 miles on it, and this is a fairly recent development. The brake pedal is going down too far when it's applied. Took the car in for service, service manager agreed the pedal is going down too far but he said everything checked out good. It's disconcerting, I'm not happy about it. Anybody have any thoughts?

I find it amazing that the Service Manager wouldn't suggest doing a brake fluid flush.

 

[Bassman]

There is a possibility, if a brake fluid flush does not do the job, that your car's vacuum booster is bad (has a tear or leak in its diaphram). This will drain brake fluid from the system and cause the brake pedal to drop down a bit.

 

[blkprlz]

There is a possibility, if a brake fluid flush does not do the job, that your car's vacuum booster is bad (has a tear or leak in its diaphram). This will drain brake fluid from the system and cause the brake pedal to drop down a bit.

+1!

 

[Justin3.6R]

If you pump the pedal does it stay up? Could be air in the system. No wet spots anywhere?

 

[LogicalPosition]

Well IF the pedal is lower than it "should" be, then there are several possibilities.

Does the pedal drop immediately upon the first pump?
Or does the pedal slowly drop while holding your foot on the brake?
Does the pedal go all the way to the floorboard? If so, quickly or slowly?
Do the brakes feel spongey, like there may be air in the lines?
Have you recently added brake fluid to the reservoir?
Have you been offroading recently, or run over debris in the roadway?
Do you live in a region that rusts vehicles?
Has anyone measured the "free play" of the brake pedal?

If you have performed no recent work on the brake system, and the vehicle just recently began showing this symptom, we can probably rule out human error from a repair.

I have seen brake hoses that puffed up(blistered) when brakes were applied causing the pedal to drop.
Or brake lines have been damaged by road debris. Inspect all hoses and hard metal brake lines.
I have seen master cylinders fail to function properly, won't hold pressure.
As mentioned above, the vacuum brake boosters can fill with brake fluid from a bad seal on the master cylinder.
Brake calipers can leak pressure past the pistons in the caliper.

Given the fact that you only have 23K miles, I honestly cannot imagine this issue is caused by anything but a failing part, and I'm gonna say it's the brake booster, especially if brake fluid is simply disappearing mysteriously.
Is there a chance the pedal itself somehow got out of adjustment?

 

[softailrider]

I find it amazing that the Service Manager wouldn't suggest doing a brake fluid flush.

He did not suggest doing that.

 

[softailrider]

Well IF the pedal is lower than it "should" be, then there are several possibilities.

Does the pedal drop immediately upon the first pump?
Or does the pedal slowly drop while holding your foot on the brake?
Does the pedal go all the way to the floorboard? If so, quickly or slowly?
Do the brakes feel spongey, like there may be air in the lines?
Have you recently added brake fluid to the reservoir?
Have you been offroading recently, or run over debris in the roadway?
Do you live in a region that rusts vehicles?
Has anyone measured the "free play" of the brake pedal?

If you have performed no recent work on the brake system, and the vehicle just recently began showing this symptom, we can probably rule out human error from a repair.

I have seen brake hoses that puffed up(blistered) when brakes were applied causing the pedal to drop.
Or brake lines have been damaged by road debris. Inspect all hoses and hard metal brake lines.
I have seen master cylinders fail to function properly, won't hold pressure.
As mentioned above, the vacuum brake boosters can fill with brake fluid from a bad seal on the master cylinder.
Brake calipers can leak pressure past the pistons in the caliper.

Given the fact that you only have 23K miles, I honestly cannot imagine this issue is caused by anything but a failing part, and I'm gonna say it's the brake booster, especially if brake fluid is simply disappearing mysteriously.
Is there a chance the pedal itself somehow got out of adjustment?

Service manager said they checked the vehicle out and didn’t find anything failing. He agreed the pedal is going down to far but he didn’t have any remedy‘s. He said there is no adjustment to raise the pedal, I asked him that.

 

[LogicalPosition]

Service manager said they checked the vehicle out and didn’t find anything failing. He agreed the pedal is going down to far but he didn’t have any remedy‘s. He said there is no adjustment to raise the pedal, I asked him that.

Without knowing EXACTLY what he and his team did, it's hard to say they didn't find a failure. There IS always a remedy. Obviously you both agreed it's not functioning as it should. "Too far" can be measured.
For them to claim there is no adjustment in the pedal play makes me skeptical, but since I haven't actually inspected the pedal in one of these newer Subaru's, I guess I'll have to trust him. I doubt there is a problem in the physical linkage or the brake pedal, but it's a simple enough question, smart of you to ask.

It could be something in the ABS, but that seems like it would throw a code and maybe a warning light on the cluster.

Bottom line in MY mind, an abrupt change in pedal drop would indicate a loss of fluid or air in the brake line. Next would be the master cylinder/power booster area.

Again, did YOU check the reservoir for fluid?
You didn't explain the FEEL of the brake pedal, instant collapse, slow drop, or spongey?
Do you have an alternate dealer to visit?

 

[hydrex]

Had a master cylinder fail in my 1998 OB. Replaced with a NAPA one and it still did the same thing. Eventually we figured the NAPA one was bad, a royal PITA. NAPA replaced it free and now brakes are perfect. Hard to believe, with 23,000 miles that could be the problem, but....

 

[Rymar]

Make sure that the caliper pins are sliding smoothly; they should be cleaned and lubricated with a good quality disk brake (hi temp) grease, at each brake service. If they are sticking, then the pads will not automatically extend as they should, each time the pedal is pressed, to adjust for pad wear. This can cause the pedal position to end up too low.

 

[apb]

Hmm... Our 2018 OB with eyesight and all whistles has had a sinking brake pedal since the day we bought it new. Dealer claimed this is normal for the fly-by-wire braking system. Brakes otherwise function well. Was I right that this should not happen, and dealer wrong? Note there has been no change in performance since we got it almost 4 years ago.

 

[Justin3.6R]

Hmm... Our 2018 OB with eyesight and all whistles has had a sinking brake pedal since the day we bought it new. Dealer claimed this is normal for the fly-by-wire braking system. Brakes otherwise function well. Was I right that this should not happen, and dealer wrong? Note there has been no change in performance since we got it almost 4 years ago.

I was told by the dealer that my screen going blank was normal. Persistence got them to replace the CCU and no problems since. I think dealers sometimes don't know their own product. Had a similar experience with a newer '88 Ford TurboCoupe and a local dealer. Basically they wanted me to pay for them to learn how to fix my car.

 

[Sub4Fun]

Air in the system makes the pedal feel spongy. The pedal should move, but start to feel firm. Spongy is not firm. If it's spongy, do what everyone else said and change out the fluid. Spongy is not drop to the floor either. Spongy will feel give you feedback, but not continue to sink.

With the car idling, press the brake pedal. It should start to move downward then become firm. If it starts to move downward after this point with any force you care to apply, then either the master cylinder is bad or the ABS dump valve in the ABS pump unit is stuck open. To diagnose which problem it's experiencing, a more subtle test is required that you may or may not be able to interpret the results of since some prior experience helps a lot.

The ABS dump valve is essentially a larger "leak" than a worn master cylinder. The ABS dump valve will cause the pedal to drop faster, but once the pedal is quite low, it will become firm and brake well. With the master cylinder issue, the pedal will eventually bleed out all of the pressure and head towards the floor/pedal travel limit.

If it's a worn master cylinder, it will need to be replaced. If it's a bad ABS dump valve, the pump will need to be replaced or rebuilt (not necessarily the electronics, but a dealer won't seperate the two). ABS pumps can fail early if brake fluid is allowed to get contaminated.

"but he said everything checked out good "
What an odd thing to say...He just said the brake pedal was low!

 

[Ken C]

The vehicle has about 23000 miles on it, and this is a fairly recent development. The brake pedal is going down too far when it's applied. Took the car in for service, service manager agreed the pedal is going down too far but he said everything checked out good. It's disconcerting, I'm not happy about it. Anybody have any thoughts?

Sinking brake pedal -- probably a worn seal inside the master cylinder.
When you step on the pedal, this pushes agains the piston in the master cylinder, which then pushes on the fluid in that master cylinder. That fluid in the master cylinder is supposed to only flow out toward the cylinders in the caliper (via the ABS, of course). Since its a closed system, that is the only way for the fluid to move, and after the caliper piston is stopped against the brake pad (which is pressed against the rotor), the fluid can't move anymore, and neither can the master cylinder's piston -- and the brake pedal also can't move, so it just stops sinking.
But if the seal in the piston of the master cylinder is worn, fluid can also flow out the "other way", back towards the master cylinder's reservior. That lets the brake pedal continue to sink as more fluid returns to the reservoir.
So you can have the pedal actually sink to the floor. Then when you release the pedal and it rises, fluid is drawn from the reservoir back into the cylinder of the master cylinder.

 

[dukey33]

I find it amazing that the Service Manager wouldn't suggest doing a brake fluid flush.

Yeah.
I find it more amazing the SM concurs the brakes aren't normal yet releases the car back to the owner with no fix. That could be considered negligent.

 

[walker]

Some other things you can test - although this is what the service department likely did, you can always double check.

brakes spongy-soft

I have drained and replaced all the brakes fluid in my impreza out back, and bled the brakes, but they are still super spongy. I have to pump the brake pedal to get them to work. Ive checked the brake lines and they are all good, but I believe the former owner disabled the ABS but cant see where...

www.subaruoutback.org