02 Envoy Soft brake pedal

1655 Views 69 Replies 12 Participants Last post by Horace P McTitties, 2 d ago

Wildvortex

Discussion Starter · 28 d ago

Ok, so this is sort of a whipped horse thing. I see many post and no real solution. I see people saying that these vehicles pedal feels very different than most vehicles.

I bought this vehicle used from a Ford dealership where my father was a salesman. He had it checked over before driving it from Maine to South Carolina to me. The mechanics there said nothing about the brakes. But, they have never felt the way I expect brakes to feel.

Several years ago I had it in the GM shop for something and nothing was ever said about the brakes

Cut to today 13 years later and about 60,000 miles later I am throwing money at the braking system. I have replaced all calipers, pads and disks. Bled, and still felt soft. With Rav's assistance we determined that I probably should replace the MC due to black brake fluid and assuming seal deterioration. I have now replaced that and gravity bled the entire system with about 3 qts of fluid (I had flushed them 6 or so months ago) as I wanted to ensure it was completely flushed. I have a scanner and did an ABS bleed 2 times. Still brakes are the way they always have been.

What I have noticed is that when I press the brake in I hear a rush of air in the cabin. It will stop as soon as I stop pushing and hold the brake without letting off of it. Is this normal with this vehicle?

1 - 20 of 70 Posts

pdcomm

· #2 · 28 d ago

This from Google :
"if you hear a hissing sound when pushing down or letting up on the brake pedal, it usually is caused by the brake booster leaking air, which could mean there's a leak in the booster diaphragm, master cylinder gasket, or vacuum hose. The brake booster relies on vacuum pressure to do its job. "

Personally , I have had similar happen . That was a vacuum problem .

Wildvortex

Discussion Starter · #3 · 28 d ago

That is understandable but, I would think that if you held the brake down then you would continue to hear that leak the entire time until you let off the brake. Not to mention that if there was a leak then pressing the pedal should be technically harder to do.

As an added note, just talked to a friend of mine who also had an envoy and his acts exactly the same. Stops well but pedal once stopped if continuing to push goes near the floor.

chem_man

· #4 · 28 d ago

I know when I had to replace the power brake booster on my 1973 Impala years ago, there really was no more air/vacuum noise after the pedal was depressed and the vehicle stopped. However, the pedal did continue to move towards the floor. If I removed my foot and allowed the pedal to return to it's regular position and then pressed down on the pedal again, there was air/vacuum noise for a few seconds and then quiet and the pedal continued to sink.

I really do not think that brake booster vacuum technology has changed much over the years.

The other thing you could try is to check the vacuum booster's check valve to make sure that it only "passes vacuum" in one direction. It's a one way valve so it should pass air in only one direction.

I'm with pdcomm on it being a vacuum problem.

Wildvortex

Discussion Starter · #5 · 28 d ago

Ok, I did check the check valve and it is good. At this point I have sunk too much into it for the month. It stops really well (almost put you through the windshield). So, like I have been I am going to drive it this way for a while. Likely won't get used much between now and October anyway. Probably will revisit it in a couple months.

chem_man

· #6 · 28 d ago

OK on the check valve.

Good Luck when you revisit the issue in a few months.

Dsport5

· #7 · 27 d ago

But...your brakes are working really well...are you sure you are not chasing a ghost?

04 Envoy I6 - I also have a soft brake pedal but I have gotten used to it

Ravalli Surfer

· #8 · 27 d ago

The rushing air sound is the atmospheric filter that lets air enter the back half -the firewall side - of the booster, equalizing pressure and therefore allowing the pedal to drop.

It usually means you have a brake pedal that is going too far to the floor and the atmospheric side of the booster is just trying to equalize things a little.

After forcing a lot of air through this filter, they can blow out and you will hear the airflow a lot louder.

Solve the over-stroking from the brake hydraulic side of the system and the rushing air sound should go away if not be significantly reduced.

You might need a rear brake adjustment (drums only) because you never use the Parking Brake - which is the way the rear brakes get adjusted (by using the Parking Brake).

Rear disc brakes don't have this system, although there is an internal expanding ring-style parking brake inside the tiny drum that runs inside the rotor.

Ravalli Surfer

· #9 · 27 d ago

Dsport5 said:
But...your brakes are working really well...are you sure you are not chasing a ghost?

04 Envoy I6 - I also have a soft brake pedal but I have gotten used to it

There is a trick to getting the air outta the ABS control System --- but Imma gonna keep it a secret until someone asks.

The brakes on my '05 TB/EXT are firm, high, and very responsive.

Ravalli Surfer

· #10 · 27 d ago

chem_man said:
I know when I had to replace the power brake booster on my 1973 Impala years ago, there really was no more air/vacuum noise after the pedal was depressed and the vehicle stopped. However, the pedal did continue to move towards the floor. If I removed my foot and allowed the pedal to return to it's regular position and then pressed down on the pedal again, there was air/vacuum noise for a few seconds and then quiet and the pedal continued to sink.

I really do not think that brake booster vacuum technology has changed much over the years.

The other thing you could try is to check the vacuum booster's check valve to make sure that it only "passes vacuum" in one direction. It's a one way valve so it should pass air in only one direction.

I'm with pdcomm on it being a vacuum problem.

Yeah - no --- and maybe.

It IS a vacuum thingy - but it is the symptom, not the problem.

Dsport5

· #11 · 27 d ago

Ravalli Surfer said:
There is a trick to getting the air outta the ABS control System --- but Imma gonna keep it a secret until someone asks.

The brakes on my '05 TB/EXT are firm, high, and very responsive.

Hmmmmm. My interest is semi-peaked.

However, I haven't delved into any brake jobs yet so it might go over my head anyways.

Here is my question, though... is there anything dangerous about my laid back brake pedals?

Ravalli Surfer

· #12 · 27 d ago

OK. After I decide if this is a pants-day or a robe-day.
..... and I can get to one of my real keyboards.

metalmike187

· #13 · 27 d ago

Ravalli Surfer said:
There is a trick to getting the air outta the ABS control System --- but Imma gonna keep it a secret until someone asks.

The brakes on my '05 TB/EXT are firm, high, and very responsive.

What's the trick on this robe day?

Ravalli Surfer

· #14 · 27 d ago

metalmike187 said:
What's the trick on this robe day?

Wait! I'm in Physical Therapy right now ...... BBS.

Ravalli Surfer

· #15 · 27 d ago

Dsport5 said:
Hmmmmm. My interest is semi-peaked.

However, I haven't delved into any brake jobs yet so it might go over my head anyways.

Here is my question, though... is there anything dangerous about my laid back brake pedals?

I'd rather you were fully-peaked and panting for an answer.

I can wait 'till then.

EDIT ---> drooling in anticipation is good too. Lemme know.

Reactions: 1

Mad Russian

· #16 · 20 d ago

A while back I decided to have more braking power for my '07 TB. I upgraded everything (except master cylinder and booster) to the brakes from the V8 (which still fits into the 17 inch wheels).
The pedal is still kind of soft, but it will stand the car on its nose if I mash it hard.
I read somewhere that if you replace the rubber lines to the wheels with stainless steel hose it firms up the pedal, but I decided it wasn't worth the expense for a truck that sits waiting for beach fishing days.

JimmyO

· #17 · 20 d ago

My 2004 XUV has had the hissing brake pedal since I bought it used in 2005 with 8000 miles. She still stops great at 140K miles.

I did replace the rotors with the drilled and slotted PowerStops Truck and Tow and flushed/filled with ATE Super Blue. Really seems to help especially when pulling a trailer in the mountains- no fade or heat buildup.

I would like to get rid of the hissing though...

Reactions: 1

Mad Russian

· #18 · 20 d ago

I had slotted rotors, they stopped but we're noisy and ate brake pads for breakfast.

Reactions: 1

JimmyO

· #19 · 20 d ago

I do hear the slots and drill holes making noise when I hammer the brakes. They are quiet when lightly used.

Same with all of my vehicles that have the PowerSlots. And my MB with slotted/drilled factory rotors does the same.

Horace P McTitties

· #20 · 18 d ago

Colloquial wisdom dictates that all noises from under the hood can be remedied by turning the radio volume up. It sounds like you covered everything except buying new Huaraches. If she stops, she stops. Former '05 TB and current '05 Envoy ownership has been consistent with the mushy feeling pedal. Even after going thru the same repairs, head scratching and posting you did. I have somehow gotten used to it again after doing the whole front side a couple weeks ago and haven't thought about them until seeing this post.

1 - 20 of 70 Posts