"Soft" brake pedal when engine running

[new2yukon]

Its going to the shop in a couple weeks. The pedal is nice and firm now with the engine off since I swapped the MC.

I've not had air that I couldn't get out via a few bleeds when I've changed hoses/calipers/pads before on my other cars so while it's frustrating I hope its as simple as the scan tool solution.

 

[YukonRog]

As pointed out, it's believed to be air in the ABS Module. Your pedal will always be stiffer with the engine off vs running because the vaccum booster isn't helping. Seems you don't want to believe that.

 

[CraftyCrafts]

My 2001 Yukon has a firm pedal when it's not running. It's considerably softer when running. Why?

No known leaks.
New front calipers.
New front brake hoses.
New master cylinder. (This helped a little)
Cycled abs via activating on dirt roads and bled all 4 wheels again.

I really don't think my service work has changed the brake feel much at all. Pedal is similar to what it's been for quite some time but my other cars are much much firmer so it seems this can be improved.

Pads are 75,000+ miles old but still have life. It stops "ok" but there's no real brake bite feeling. New pads/rotors prob would help this but when idling those are irrelevant.

Wondering about air somewhere but the pedal is firm with everything off.

Thanks in advance.

Brake booster check valve or power brake booster itself if re-bleeding doesn't solve it.

 

[Neal54521]

My 2001 Yukon has a firm pedal when it's not running. It's considerably softer when running. Why?

No known leaks.
New front calipers.
New front brake hoses.
New master cylinder. (This helped a little)
Cycled abs via activating on dirt roads and bled all 4 wheels again.

I really don't think my service work has changed the brake feel much at all. Pedal is similar to what it's been for quite some time but my other cars are much much firmer so it seems this can be improved.

Pads are 75,000+ miles old but still have life. It stops "ok" but there's no real brake bite feeling. New pads/rotors prob would help this but when idling those are irrelevant.

Wondering about air somewhere but the pedal is firm with everything off.

Thanks in advance.

Hey I have an 01 Tahoe same problem I’ve changed everything except the abs and still soft to idk what it can be even vacuum booster change I’m maybe thinking vacuum leak on intake cause brakes are a lil better after I’m on the freeway and build vacuum just irritating lol

 

[new2yukon]

As pointed out, it's believed to be air in the ABS Module. Your pedal will always be stiffer with the engine off vs running because the vaccum booster isn't helping. Seems you don't want to believe that.

It is certainly clear you have not read all the posts. You're not helping, nor do you know what I believe. In not stupid; this is not my first brake work, nor do I pretend to know it all. Thanks, but not.

 

[new2yukon]

Hey I have an 01 Tahoe same problem I’ve changed everything except the abs and still soft to idk what it can be even vacuum booster change I’m maybe thinking vacuum leak on intake cause brakes are a lil better after I’m on the freeway and build vacuum just irritating lol

You can PM me for more thoughts and what I've done and diagnosing. Posting can sometimes yield derogatory comments rather rapidly.

 

[Scottydoggs]

You can PM me for more thoughts and what I've done and diagnosing. Posting can sometimes yield derogatory comments rather rapidly.

you really need to have thicker skin. ppl aren't trying to bash you or nothin they are just giving an opinion regarding the help you "asked" for. when you feel well that reply dont apply, scroll to the next post.

remember none of us are there with your truck, anything said is nothing more then a educated guess when it comes to forums.

 

[new2yukon]

you really need to have thicker skin. ppl aren't trying to bash you or nothin they are just giving an opinion regarding the help you "asked" for. when you feel well that reply dont apply, scroll to the next post.

remember none of us are there with your truck, anything said is nothing more then a educated guess when it comes to forums.

Haha. Have thick enough skin do I? I know that stupid-axx people tell me its air in the abs without even acknowledging other potential parts, which, I will say, can and do display the same symptoms. Nor read what I've posted. Irrelevant half-axx comments don't help anyone.

Telling me I dont want to believe what the solution is just confirms one's lack of understanding and intellect.

Your diareah you have next month is your shirt color you choose, just sayin. I've given you a proper diagnosis even you just don't want to believe that's the answer.

 

[Fless]

Well, that attitude will certainly encourage people to provide information based on their experiences and how they understand the issue. Or not.

@Scottydoggs was right in saying that people will suggest things based on their experiences and what they've read. And yes, unfortunately they don't always read the details and the back story, or maybe don't understand what was said, but they try to contribute. Just a fact of these types of forums, attempting to diagnose without being in-person, from a distance, with limited info. Just ignore those and move ahead. (I know there is some frustration with that, but it's the nature of the forum beast.)

Carry on.

 

[Scottydoggs]

Haha. Have thick enough skin do I? I know that stupid-axx people tell me its air in the abs without even acknowledging other potential parts, which, I will say, can and do display the same symptoms. Nor read what I've posted. Irrelevant half-axx comments don't help anyone.

Telling me I dont want to believe what the solution is just confirms one's lack of understanding and intellect.

Your diareah you have next month is your shirt color you choose, just sayin. I've given you a proper diagnosis even you just don't want to believe that's the answer.

i can tell you this. if the master drained at any time, you likely got air in the abs pump.