Chevy Bolt EV Forum banner

21 - 40 of 42 Posts

·
Registered
Joined
·
2 Posts
Just got my 2018 Bolt back from the Chevy dealer warranty repair where they fixed the same clicking sound by replacing the SL-N-Cylinder (04650-C) and its fluid. They also replaced the brake booster control module assembly. My service advisor said the parts would have been over $1200 + labor. He also said the tech found the issue in this forum and not on the Chevy service bulletin website. Thanks to everyone who gave answers to this issue. The dealer also said that Bolt/Volt forums are more active then all of the other Chevy forums.
 

·
Registered
Joined
·
6 Posts
SL-N-Cylinder (04650-C)
Its a master cylinder, right?

They also replaced the brake booster control module assembly
You mean the brake booster control module itself OR you mean the assembly = booster+master cylinder+brake pedal assembly ?

My service advisor said the parts would have been over $1200 + labor
That is why I'm not keen yet to replace it (warranty not valid for my car anymore).

Pharlyn, could you please ask your service advisor:
  • if they consider it as failure which might cause later more serious malfunction of the brakes OR its annoying thing only, I mean the clicking sound?
  • if they could dismantle all the assembly (or at least the iBooster) apart to carefully inspect what exactly has failed?
  • if they are going to discard everything they dismantled maybe they could sell it to me for some symbolic price?
 

·
Registered
Joined
·
2 Posts
Its a master cylinder, right?

I typed exactly what my receipt said. I assume it is the master cylinder.

You mean the brake booster control module itself OR you mean the assembly = booster+master cylinder+brake pedal assembly ?

Only the brake booster control module as the receipt did not list a brake pedal assembly.

That is why I'm not keen yet to replace it (warranty not valid for my car anymore).

Pharlyn, could you please ask your service advisor:
  • if they consider it as failure which might cause later more serious malfunction of the brakes OR its annoying thing only, I mean the clicking sound?
  • if they could dismantle all the assembly (or at least the iBooster) apart to carefully inspect what exactly has failed?
  • if they are going to discard everything they dismantled maybe they could sell it to me for some symbolic price?

Anytime you have gears that are constantly moving against each other when the car in not moving says to me that they will eventually wear out.

My experience with warranty repairs with dealers is they need to send the broken parts back to Chevy so they can go to the manufacture to recover their cost and get them to improve the part.

I wish you all the best in your non-warranty repair.
 

·
Registered
Joined
·
34 Posts
Took my 2017 Bolt into the shop today with the brake booster tapping noise. They "DIAGNOSED AND ORDERED BRAKE BOOSTER/MASTERC YLINDER ASSEMBLY AND PUSH ROD RETAINER"

Sadly, the part is on order and may take a few days (weeks?) to arrive due to the GM strike since parts suppliers shut down, too. Happily, it will be a warranty repair.

Thanks to all in the thread for sharing the symptoms and diagnosis.
 

·
Registered
Joined
·
2,316 Posts
Took my 2017 Bolt into the shop today with the brake booster tapping noise. They "DIAGNOSED AND ORDERED BRAKE BOOSTER/MASTERC YLINDER ASSEMBLY AND PUSH ROD RETAINER"

Sadly, the part is on order and may take a few days (weeks?) to arrive due to the GM strike since parts suppliers shut down, too. Happily, it will be a warranty repair.

Thanks to all in the thread for sharing the symptoms and diagnosis.
Fortunately, with the Bolt, you may not need to use your brakes. ;)
 

·
Registered
Joined
·
4 Posts
Mine just was replaced, under warranty. I Booster Bosch Brake Module, now quiet vehicle with no more low thumping sound at rest.
GM Bolt Central is well aware of this problem; dealers not so much.
Would there be any way you could email me a copy of your service bill? My Bolt is doing the same thing. Last time when I had the rear axle problem, I showed them a Bolt forums service record and they immediately repaired the problem. They thanked me profusely for bringing the other person's service info. My Bolt seems to get every problem, sadly.
 

·
Registered
Joined
·
1 Posts
Started noticing this same tapping sound in my Bolt a few weeks ago and my local dealer has just confirmed the source is the brake booster. Unfortunately for me, the warranty covering the brake system is up on this car and dealer quoted $2K to replace the booster assembly. I’m curious if anyone has confirmed if this is truly a safety consideration or not? Or if anyone has this problem and decided to leave it alone and what the outcome was? My understanding is the Bolt’s regenerative braking will continue to function even if the brake booster were to fail since they are separate systems but I think there are still scenarios where friction braking is important. It’s not clear to me from booster documentation how functional the hydraulic brakes would be without the booster working.

I talked with the certified Bolt tech at this dealer and he simply couldn’t tell me if this sound was a sign of impending booster failure or not where the tapping sound was coming from specifically within the assembly. Judging from the video linked earlier in the thread, I’d guess the sound is coming from the input rod sliding up against one or the other limit of the boost body. Doesn’t really give me any insight into why the problem would suddenly appear or if it has long term consequences though. Has anyone managed to learn more about this failure mode?

I’m also curious if anyone else has had this job done not under warranty and if the price I’m being offered is comparable?

Appreciate any information. This thread was tremendously helpful in guiding the service folks to the problem quickly.
 

·
Registered
Joined
·
120 Posts
Started noticing this same tapping sound in my Bolt a few weeks ago and my local dealer has just confirmed the source is the brake booster. Unfortunately for me, the warranty covering the brake system is up on this car and dealer quoted $2K to replace the booster assembly. I’m curious if anyone has confirmed if this is truly a safety consideration or not? Or if anyone has this problem and decided to leave it alone and what the outcome was? My understanding is the Bolt’s regenerative braking will continue to function even if the brake booster were to fail since they are separate systems but I think there are still scenarios where friction braking is important. It’s not clear to me from booster documentation how functional the hydraulic brakes would be without the booster working.

I talked with the certified Bolt tech at this dealer and he simply couldn’t tell me if this sound was a sign of impending booster failure or not where the tapping sound was coming from specifically within the assembly. Judging from the video linked earlier in the thread, I’d guess the sound is coming from the input rod sliding up against one or the other limit of the boost body. Doesn’t really give me any insight into why the problem would suddenly appear or if it has long term consequences though. Has anyone managed to learn more about this failure mode?

I’m also curious if anyone else has had this job done not under warranty and if the price I’m being offered is comparable?

Appreciate any information. This thread was tremendously helpful in guiding the service folks to the problem quickly.
My brake Booster Module has been replaced Twice, under warranty. Sorry I can't help you on the non warranty pricing.
I don't think I could live with the sound, day after day.
Comparison shopping, perhaps with an Indie Shop, might be in order.
 

·
Registered
Joined
·
5,738 Posts
My understanding is the Bolt’s regenerative braking will continue to function even if the brake booster were to fail since they are separate systems but I think there are still scenarios where friction braking is important. It’s not clear to me from booster documentation how functional the hydraulic brakes would be without the booster working.
You could pull the electric brake boost motor source fuse in the underhood fuse box. It is fuse 29. This should allow you to do a controlled test. I don't know what codes it might throw however, and whether you can just clear them by turning the car on and off ten times, or whether the dealer would need to clear them.
 

·
Registered
Joined
·
1 Posts
I have the exact same problem on my 2018. I took it to the dealer and they can hear the problem but told me that it's not an issue with performance of the car and they can't get approval from GM to fix the issue. They said that without approval they can't guarantee they will be reimbursed. Complete BS. I'm going to find a certified Chevy EV dealer that has a mechanic and try my luck there. It's a nonstop clicking even when the car is off. It only stops once the brake is pressed, so I'm confident that it's the exact same issue. I've also noticed that the regen brake is not as effective.
 

·
Registered
Joined
·
120 Posts
I have the exact same problem on my 2018. I took it to the dealer and they can hear the problem but told me that it's not an issue with performance of the car and they can't get approval from GM to fix the issue. They said that without approval they can't guarantee they will be reimbursed. Complete BS. I'm going to find a certified Chevy EV dealer that has a mechanic and try my luck there. It's a nonstop clicking even when the car is off. It only stops once the brake is pressed, so I'm confident that it's the exact same issue. I've also noticed that the regen brake is not as effective.
Boy, thats a new one on me, not replacing because its "not an issue with performance"
Get it replaced, under warranty.
 

·
Registered
Joined
·
6 Posts
Update after almost a year with this annoying ticking/clicking noise:
1) I ended up by replacing the iBooster two times, both times with a used one. I did everything by myself. If you need advices for the replacement I'll be glad to help you.
2) I disassembled the original iBooster to inspect what was wrong with the internals. Mechanically everything looks in perfect condition, no signs of wear of any of gears. So definitely the attached electronics or the attached position sensor failed. You can change this sensor but to do that anyway to have to remove the full brake booster first to gain access to it.
 

·
Registered
Joined
·
5,738 Posts
Update after almost a year with this annoying ticking/clicking noise:
1) I ended up by replacing the iBooster two times, both times with a used one. I did everything by myself. If you need advices for the replacement I'll be glad to help you.
2) I disassembled the original iBooster to inspect what was wrong with the internals. Mechanically everything looks in perfect condition, no signs of wear of any of gears. So definitely the attached electronics or the attached position sensor failed. You can change this sensor but to do that anyway to have to remove the full brake booster first to gain access to it.

Thank you for getting to the bottom of the Bosch i-Boost failures!
 

·
Registered
Joined
·
1 Posts
In my Volt it happens at rest too. As well I can hear it in some intervals when moving up to 20mi/h speed. I guess it is always there simply I do not hear it later anymore because other noises (wind and tires) are more loud.
I just received a 2020 Bolt and when I stop the car and step outside I notice a frantic clicking under the hood (not inside).
is this the same problem or different?
it ends after 1-2 minutes and it starts again when I unlock the car in the morning.
 

·
Registered
Joined
·
5,738 Posts
I just received a 2020 Bolt and when I stop the car and step outside I notice a frantic clicking under the hood (not inside).
is this the same problem or different?
it ends after 1-2 minutes and it starts again when I unlock the car in the morning.
There is a very easy way to answer your own question. Open the hood and stick your ear near the brake master cylinder. It is indicated by the brake fluid label in this picture.


Also, if your step on the brake it stops.
 

·
Registered
Joined
·
1 Posts
My 2018 Volt Premier with 6200 miles is in the shop at the moment for this very reason. They just called to say they ordered the part and not sure when they'll get it. They told me I can come get the car and drive it for now without problems. Hope it doesn't take too long.
 

·
Registered
Joined
·
1 Posts
Started noticing this same tapping sound in my Bolt a few weeks ago and my local dealer has just confirmed the source is the brake booster. Unfortunately for me, the warranty covering the brake system is up on this car and dealer quoted $2K to replace the booster assembly. I’m curious if anyone has confirmed if this is truly a safety consideration or not? Or if anyone has this problem and decided to leave it alone and what the outcome was? My understanding is the Bolt’s regenerative braking will continue to function even if the brake booster were to fail since they are separate systems but I think there are still scenarios where friction braking is important. It’s not clear to me from booster documentation how functional the hydraulic brakes would be without the booster working.

I talked with the certified Bolt tech at this dealer and he simply couldn’t tell me if this sound was a sign of impending booster failure or not where the tapping sound was coming from specifically within the assembly. Judging from the video linked earlier in the thread, I’d guess the sound is coming from the input rod sliding up against one or the other limit of the boost body. Doesn’t really give me any insight into why the problem would suddenly appear or if it has long term consequences though. Has anyone managed to learn more about this failure mode?

I’m also curious if anyone else has had this job done not under warranty and if the price I’m being offered is comparable?

Appreciate any information. This thread was tremendously helpful in guiding the service folks to the problem quickly.
We have 2017 both a Bolt and a Volt. The Volt has this problem and they told me $2000 also. I was going to go on a trip this week but I'm afraid to use this car. I don't feel comfortable going with the Bolt by myself because there are not a lot of stations on my way. Looks like I don't have a choice because I haven't heard back from Chevy on if they have the part and how long it will take to fix. I will call them one more time tomorrow.

I've heard conflicting opinions on whether it is safe to drive. I don't know why I've had no warning lights go on. In fact when I took it in she said it was fine until I showed her the noise then they found the $2000 problem. Mine also is not under warranty any more.

I appreciate everyone's comments. Any idea how many have to have problems before it becomes a recall?
 

·
Registered
Joined
·
116 Posts
I just started having this exact issue. Constant tapping (I thought it was part of the music at first) that disappears if I hold down the brakes. Happens with the car stopped as well. Guess I'm making a dealer appointment. 25k miles. Reading around, it looks like the typical potential fight with the dealer and then they put an exact same $1200 unit in that will probably fail again out of warranty. Wonderful.
 
21 - 40 of 42 Posts
Top