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Got an interesting one for the forum. After the truck (2016 GMC Sierra) has been sitting a while (usually over night or for a few hours) the pedal let's out a nice squeak. On rare occasions I can get it to do it twice in a row, but most of the time the squeak is only for the first press then is gone for all the other presses. Normal daily driving I don't hear it, it's only the first press or when I have to hit my brakes hard (ex, cut off by someone). My local dealer service department (who's treated me well and has good mechanics) looked at it and said they can't repeat it enough to truly diagnose it. Some squeaks are real quick and others last about 2 seconds. The only way I can describe it is like a relief valve letting some air out, but with a squeak. Sometimes I can hold the pedal in place after depressing and the squeak continues to let out. It's not like a metal plunger rubbing on a rubber boot as I depress the pedal, plus I would be able to make the sound every time if that were the case.

 

Below is a video I took on two different occasions, they are looped a couple times. You'll hear what I'm talking about and see that it's gone on the second press. I did have the vacuum pump replaced due to the recall about a year ago, I noticed it after that but the dealership said the pump and vacuum is holding well the entire time, even when it squeaks. They only guess they had was to replace the brake pedal assembly or the brake booster, but admittedly said that would just be throwing parts at it. Just got the truck back today, didn't get charged for the diagnosis since they couldn't figure it out. Now I'm turning to the forum. Any idea what's going on?!?

 

 

Edited by midwestdenaliguy
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3 hours ago, midwestdenaliguy said:

Got an interesting one for the forum. After the truck (2016 GMC Sierra) has been sitting a while (usually over night or for a few hours) the pedal let's out a nice squeak. On rare occasions I can get it to do it twice in a row, but most of the time the squeak is only for the first press then is gone for all the other presses. Normal daily driving I don't hear it, it's only the first press or when I have to hit my brakes hard (ex, cut off by someone). My local dealer service department (who's treated me well and has good mechanics) looked at it and said they can't repeat it enough to truly diagnose it. Some squeaks are real quick and others last about 2 seconds. The only way I can describe it is like a relief valve letting some air out, but with a squeak. Sometimes I can hold the pedal in place after depressing and the squeak continues to let out. It's not like a metal plunger rubbing on a rubber boot as I depress the pedal, plus I would be able to make the sound every time if that were the case.

 

Below is a video I took on two different occasions, they are looped a couple times. You'll hear what I'm talking about and see that it's gone on the second press. I did have the vacuum pump replaced due to the recall about a year ago, I noticed it after that but the dealership said the pump and vacuum is holding well the entire time, even when it squeaks. They only guess they had was to replace the brake pedal assembly or the brake booster, but admittedly said that would just be throwing parts at it. Just got the truck back today, didn't get charged for the diagnosis since they couldn't figure it out. Now I'm turning to the forum. Any ideas what's going on?!?

 

 

Does it make the noise if you move the pedals to another position, you should have the adjustable set with the Denali. 

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10 hours ago, JimCost2014 said:

Does it make the noise if you move the pedals to another position, you should have the adjustable set with the Denali. 

You are correct, I have the adjustable pedals. Unfortunately the squeak happens no matter where I have the pedals - tried them all the way down, up, and in between. It still happens.

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2 hours ago, JimCost2014 said:

I would  imagine this is the next step, if there are no lube points on the assembly.

Everything has been hit with lube by myself and the technicians in the service department, squeak is still there. I can get the entire adjustable brake assembly for $120, so I'm now at the point of throwing that at it to see if it fixes it. Know much about a job like that? Seems to be plug and play, but don't want to assume anything and create a mess for myself. I've searched high and low and can't find anything on someone replacing the brake pedal assembly.

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3 hours ago, midwestdenaliguy said:

Everything has been hit with lube by myself and the technicians in the service department, squeak is still there. I can get the entire adjustable brake assembly for $120, so I'm now at the point of throwing that at it to see if it fixes it. Know much about a job like that? Seems to be plug and play, but don't want to assume anything and create a mess for myself. I've searched high and low and can't find anything on someone replacing the brake pedal assembly.

 

3 hours ago, midwestdenaliguy said:

Everything has been hit with lube by myself and the technicians in the service department, squeak is still there. I can get the entire adjustable brake assembly for $120, so I'm now at the point of throwing that at it to see if it fixes it. Know much about a job like that? Seems to be plug and play, but don't want to assume anything and create a mess for myself. I've searched high and low and can't find anything on someone replacing the brake pedal assembly.

The dealership didn't know what to do with this? You have a leaking diaphragm. I repair these all the time. They are really bad on the Acadia,Traverse,Enclaves. Replace the brake booster assembly. If you have a hydro booster let me know and I will explain to you how to do it on that because the diaphragm is different on those.

 

What is happening is when it sits a long time the rod slips in the diaphragm and after you press it, it reseats it. That's also why you can press it extremely hard and get it to make the noise. 

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13 hours ago, carnau said:

 

The dealership didn't know what to do with this? You have a leaking diaphragm. I repair these all the time. They are really bad on the Acadia,Traverse,Enclaves. Replace the brake booster assembly. If you have a hydro booster let me know and I will explain to you how to do it on that because the diaphragm is different on those.

 

What is happening is when it sits a long time the rod slips in the diaphragm and after you press it, it reseats it. That's also why you can press it extremely hard and get it to make the noise. 

Thank God, someone knows what's going on! How do I know if I have a hydro booster? Never replaced a brake booster assembly but I have the tools to do just about any job and have been doing regular maintenance and repairs on all my vehicles since I was a teenager. Unless you truly think this should be left to a technician, this a big job? Shoot me straight, won't hurt my feelings. 

 

Also, how do I know replacing the booster with another oem booster won't lead to the issue again? You get many returns with another bad diaphragm? Is there an aftermarket replacement to consider?

Edited by midwestdenaliguy
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20 hours ago, midwestdenaliguy said:

Thank God, someone knows what's going on! How do I know if I have a hydro booster? Never replaced a brake booster assembly but I have the tools to do just about any job and have been doing regular maintenance and repairs on all my vehicles since I was a teenager. Unless you truly think this should be left to a technician, this a big job? Shoot me straight, won't hurt my feelings. 

 

Also, how do I know replacing the booster with another oem booster won't lead to the issue again? You get many returns with another bad diaphragm? Is there an aftermarket replacement to consider?

Ok. So the reason this happened (or should I say the most common reason) is because someone pressed the brake pedal really hard (maybe getting into an accident. That's where I see it the most) The new OEM booster can absolutely have this happen again. More than likely you won't have this happen again. But it is man made. Things break. That's why I got a job.

 

Is it a 2500 diesel? If it is a 1500 you dont have a hydro booster. Vacuum Boosters are easy to replace. You remove the master cylinder (do not disconnect the brake lines) it has 2 bolts holding it on. Disconnect the vacuum. Take the through rod loose from the brake pedal assembly (it has one 10mm bolt and a slide to hold the BPPS on) and then you remove four 15mm nuts and the booster comes right off. 


No you can ABSOLUTELY do this yourself. It is super easy. https://amzn.to/2NO9OfW is the part you need.

 

Here is a video (I know it is a 2006 but the principles are the same.) You don't have to adjust the rod depth though on a 2016. 

 

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7 minutes ago, carnau said:

Ok. So the reason this happened (or should I say the most common reason) is because someone pressed the brake pedal really hard (maybe getting into an accident. That's where I see it the most) The new OEM booster can absolutely have this happen again. More than likely you won't have this happen again. But it is man made. Things break. That's why I got a job.

 

Is it a 2500 diesel? If it is a 1500 you dont have a hydro booster. Vacuum Boosters are easy to replace. You remove the master cylinder (do not disconnect the brake lines) it has 2 bolts holding it on. Disconnect the vacuum. Take the through rod loose from the brake pedal assembly (it has one 10mm bolt and a slide to hold the BPPS on) and then you remove four 15mm nuts and the booster comes right off. 


No you can ABSOLUTELY do this yourself. It is super easy. https://amzn.to/2NO9OfW is the part you need.

 

Here is a video (I know it is a 2006 but the principles are the same.) You don't have to adjust the rod depth though on a 2016. 

 

Pressing the pedal really hard makes complete sense, I had the vacuum pump issue and had to nearly stand on my pedal a couple times to get the truck to stop before hitting someone (I'm 6'4" 220 lbs so lots of pressure). Vacuum pump was replaced as part of the recall. That would also explain why the squeak showed up after it was replaced because I took it in right after I had to stand on the brakes, I didn't drive it any more until I felt it was safe.

 

I have a 1500 so no hydro. Wow, based on your instructions this will be a simple plug and play. Thanks for the part link and video. I'll be tackling this by next week at the latest. Really appreciate the help, I'd buy you a case of beer if we lived closer. Cheers.

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46 minutes ago, midwestdenaliguy said:

Pressing the pedal really hard makes complete sense, I had the vacuum pump issue and had to nearly stand on my pedal a couple times to get the truck to stop before hitting someone (I'm 6'4" 220 lbs so lots of pressure). Vacuum pump was replaced as part of the recall. That would also explain why the squeak showed up after it was replaced because I took it in right after I had to stand on the brakes, I didn't drive it any more until I felt it was safe.

 

I have a 1500 so no hydro. Wow, based on your instructions this will be a simple plug and play. Thanks for the part link and video. I'll be tackling this by next week at the latest. Really appreciate the help, I'd buy you a case of beer if we lived closer. Cheers.

No problem. Glad I could help.

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UPDATE - Installed a new OEM ACDelco brake booster (part # 178-0922 or 23135220), with new gasket (part # 15974046) and no more squeak! Thanks again Carnau, install was a breeze. Total cost with both parts shipped to my door was $107. Ordered both through Amazon because their cost was on par with OEM parts websites, but had quicker shipping with 2-day delivery. 

 

Anyone who's considering doing this job yourself...it can easily be done as long as you have a 15mm deep socket and some socket extensions. Only semi painful part was getting to the booster bolts behind the brake pedal assembly, it's tight getting a deep socket in there. Overall an easy job though that's 7x cheaper than going through dealer (was quoted $700 for them to do it).

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On 7/5/2020 at 11:16 PM, midwestdenaliguy said:

UPDATE - Installed a new OEM ACDelco brake booster (part # 178-0922 or 23135220), with new gasket (part # 15974046) and no more squeak! Thanks again Carnau, install was a breeze. Total cost with both parts shipped to my door was $107. Ordered both through Amazon because their cost was on par with OEM parts websites, but had quicker shipping with 2-day delivery. 

 

Anyone who's considering doing this job yourself...it can easily be done as long as you have a 15mm deep socket and some socket extensions. Only semi painful part was getting to the booster bolts behind the brake pedal assembly, it's tight getting a deep socket in there. Overall an easy job though that's 7x cheaper than going through dealer (was quoted $700 for them to do it).

Great man! I am so glad it helped! NOW SEND ME SOME MONEY! ?

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14 hours ago, carnau said:

Great man! I am so glad it helped! NOW SEND ME SOME MONEY! ?

Ha, just creeped your YouTube channel. Awesome stuff man, can only imagine how much you've saved people both headache and cost wise with all your how-to repair videos. Just sent you a little something to support the channel, keep the content coming! Cheers brother.

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2 hours ago, midwestdenaliguy said:

Ha, just creeped your YouTube channel. Awesome stuff man, can only imagine how much you've saved people both headache and cost wise with all your how-to repair videos. Just sent you a little something to support the channel, keep the content coming! Cheers brother.

WOW! Thanks so much! I was completely kidding. I really do appreciate it, you didn't have to! Thanks again!

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