[GarBec]

You can't start?


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It's not that I cannot start it with the keyless push button: Because there is a lack of residual stored vacuum in the power brake booster, (it apparently leaks down after a few hours, or overnight) the brake pedal is extremely difficult to depress to facilitate starting with the push button. As soon as it is started, the vacuum is restored to the booster chamber, and it functions normally for a short time. When letting it sit overnight, and attempting to depress the brake pedal before starting, the pedal doesn't give under your foot at all; rock hard! The same condition can be duplicated by depressing the brake pedal about 5 times after shutting the engine off. This also will deplete the stored vacuum in the brake booster reservoir. The reason that the reservoir exists is so you have a functioning service brake if the engine were to shut off while driving. If the vehicle didn't have keyless push button start, I probably would not have noticed a problem existed, as you only need to turn the key to start the key start systems, depressing the brake pedal isn't necessary to start the vehicle.

 

[cp-the-nerd]

I notice this with my 2015 SS sedan and it may be a leak in the brake booster...but mine's only done this when starting the car and only on occasion...

Bill

Same here. I just assumed the big brembos are too demanding when the car's off.

 

[perfectreign]

Because there is a lack of residual stored vacuum in the power brake booster, the brake pedal is extremely difficult to depress to facilitate starting with the push button.

OIC

I have resistance on all my cars/trucks since i first got power brakes in my '95 GMC Jimmy through our Maxima, Avalanche, Kia Sedona, and my '00 Jetta TDI. I think you should bring it in or at least run a scan.


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[GarBec]

OIC

I have resistance on all my cars/trucks since i first got power brakes in my '95 GMC Jimmy through our Maxima, Avalanche, Kia Sedona, and my '00 Jetta TDI. I think you should bring it in or at least run a scan.


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I have 5 other GM vehicles in the family. A few of them sometimes aren't driven for over a month or more at a time. I can get in any of the others, and at any time have vacuum assist for a few applications of the brake pedal prior to the reserve vacuum stored in the brake booster to be depleted. Try this little experiment: After running your engine, shut it off and then repeatedly depress the brake pedal. At first the pedal will give slightly under pressure from your foot, after about the sixth application the pedal will not give at all under your foot, signaling the vacuum is depleted in the booster reservoir. This is how I find my Malibu after attempting to start after sitting idle overnight. In order to facilitate a start with this push button start system, first I must apply the brake pedal, then press the start button. When attempting to depress the pedal on our Malibu, it does not depress because apparently the vacuum booster reservoir no longer contains any vacuum. I hope that I have explained my observations so that you may understand why I perceive to have a legitimate issue. I don't know if a scan would show a problem in this system or not, although there appears to be an electrical sender of some sort at the vacuum port on the booster itself.

I have a service appointment in the morning; maybe I'll get some answers to share with the Forum.

 

[GarBec]

Well I just returned from my service appointment regarding my brake booster issue, here is the diagnosis:

"397 TEST THE BRAKE OPERATION
FOUND THE BRAKE BOOSTER IS LOSING RESERVE VACUUM
INSPECT FOR VACUUM LEAKS AND FOUND THE BRAKE BOOSTER TO BRAKE MASTER CYLINDER SEAL LEAKING
ORDERED PARTS FOR THE REPAIR"

The part ordered was a complete brake booster assembly.

When attempting to explain the symptoms to the service writer, and describing the apparent loss of vacuum in the booster, this is his response: "If there was no vacuum in the brake booster, the brake pedal would go to the floor."
My response to this was: "No, that isn't how it works, if it was a hydraulic system issue that may be the case." He then transferred me to a female advisor that actually listened to my explanation. Apparently she relayed the info sufficiently to the technician who then made the diagnosis.

I'll post after the repair to share the results.

Thanks to all who made comments, suggestions, and observations regarding this issue.

 

[DrivenDaily]

Glad it helped you understand your car better and hope it helped when you were there in the service department.

Let us know how it finally turns out. I'll bet starting the car will be more of a dream than a nightmare when it's done!

 

[GarBec]

Update on the brake booster issue:

I had a new brake booster assembly installed, the brakes were bled, and the fuel trim was checked/reset. I went out the next morning after the repair and the problem has not changed. There is no vacuum in the booster reservoir after sitting overnight. I got a call from the dealer's customer service department to ask if everything was okay now; to which I responded that we haven't resolved the problem yet. I haven't scheduled a followup visit as of yet, as I was on vacation for a week, out of town. I'm not that concerned about the safety aspect, as the brakes work just fine, and after shutting the engine off, I have reserve vacuum available to operate the brakes with the engine off. It's only after sitting a number of hours or overnight that the problem exists.

If any of the Forum members here have the 1.5 turbo with the push button start; see if you are able to easily depress the brake pedal to facilitate a start, preferably after the engine hasn't been started numerous hours or overnight. (Mine is hard, cannot easily depress)

If I shut off the engine and immediately depress the pedal; I can depress it about 6 times before it gets firm/hard to depress, signifying depletion of residual reserve vacuum in the booster.

When attempting to depress the pedal after the vehicle has been off for numerous hours, the pedal is firm/hard on the first application of the brake. I cannot be made to believe that this is normal.

With a little feedback from some of you willing to see if yours operates the same way. Maybe I can determine what constitutes normal operation.

 

[DrivenDaily]

With that new booster assembly, did it come with a new 1-way check valve and a new grommet? If not, that could be the whole issue.

Or not...

It sure sounds like there's just one little piece of this puzzle that's being overlooked, and it's probably been staring us all in the face the whole time!

 

[campb292]

If any of the Forum members here have the 1.5 turbo with the push button start; see if you are able to easily depress the brake pedal to facilitate a start, preferably after the engine hasn't been started numerous hours or overnight. (Mine is hard, cannot easily depress)

If I park overnight the brake pedal remains easy to depress. If I leave it at an airport for 3 days it remains easy to depress. Of all the rental Malibus I have been in, all 1.5T cars, all have been easy to depress after being parked overnight.

With a little feedback from some of you willing to see if yours operates the same way. Maybe I can determine what constitutes normal operation.

I don't recommend getting sidetracked into thinking what you are experiencing is normal; Your dealer already diagnosed it as not normal. In my experience the loss of reserve vacuum overnight is not normal. The trick is figuring out where the issue is (see @DrivenDaily comments). I am curious, how is Hill-Start Assist working? If you stop on a moderate incline, let auto stop engage, then let off the brake do you stay stopped for at least two seconds before moving forward? No roll back?

 

[tnmats]

If I park overnight the brake pedal remains easy to depress. If I leave it at an airport for 3 days it remains easy to depress. Of all the rental Malibus I have been in, all 1.5T cars, all have been easy to depress after being parked overnight.

Same with my '17 Premier, it will retain the brake boost assist after being parked for days.

 

[GarBec]

With that new booster assembly, did it come with a new 1-way check valve and a new grommet? If not, that could be the whole issue.

Or not...

It sure sounds like there's just one little piece of this puzzle that's being overlooked, and it's probably been staring us all in the face the whole time!

I have the same exact thoughts. My service advisor claims that the assembly included everything including the check valve, but I have my doubts. I marked the booster before hand; it has been replaced, everything else, I have no clue. The valve and grommet to me were the first things I would suspect.

 

[GarBec]

I don't recommend getting sidetracked into thinking what you are experiencing is normal; Your dealer already diagnosed it as not normal. In my experience the loss of reserve vacuum overnight is not normal. The trick is figuring out where the issue is (see @DrivenDaily comments). I am curious, how is Hill-Start Assist working? If you stop on a moderate incline, let auto stop engage, then let off the brake do you stay stopped for at least two seconds before moving forward? No roll back?

I totally agree, It definitely is not a normal condition; four of my other GM vehicles don't exhibit this problem, I don't expect this one to function any differently.

Regarding the hill hold feature, I haven't tested that feature yet. I am curious too if it will function; I believe that it probably will work, as I have plenty of residual reserve vacuum available after shutting the engine off. I've shut the engine off, and immediately depressed the brake pedal until the reserve is depleted. It takes at least 6 pedal strokes to deplete the residual vacuum. Even after an hour, I still have reserve vacuum. It's when sitting idle 5 or more hours that the reserve is noticeably deficient. It would be interesting to tap a vacuum gauge into the booster and observe the loss as it happens.

 

[Dale_K]

I think there is an electric vacuum pump somewhere under the hood to provide vacuum for the brakes during periods when there is no intake manifold vacuum. Maybe that's not working. Just a guess from the internet.

 

[GarBec]

My Malibu is vacationing at my dealership while the technician is trying to determine why, after replacing the brake booster assembly, check valve, and tubing; there still is a loss of residual vacuum in the brake booster. The latest attempt to resolve this was to inspect/replace the o-ring seal between the master cylinder and brake booster. He's used a smoke/leak detector for diagnostic purposes, but still there is a loss of vacuum when sitting idle for a few hours. I was notified Friday that they were getting GM tech support involved on Monday. Meanwhile I was given a new 2018 2.0 turbo Equinox LT as a loaner. (The 2.0 turbo makes the E-Nox come alive; I can imagine how potent it is in the Malibu Premier)

 

[SilverSport]

hope they get your issue resolved...on the Equinox...I have read great things about the new Equinox, especially with the 2.0T...please share that experience after your Malibu issues get settled...

Bill

 

[campb292]

I was notified Friday that they were getting GM tech support involved on Monday.

That should really help. Let us know the outcome.

As for the Equinox, I had a 1.5T AWD version a couple weeks ago. Being 500 lbs heavier than the Malibu but only a few hp more didn't make for a robust experience. The vehicle itself seemed comfortable and it was a bit quieter than the Malibu. It is a pretty major change from the previous gen... it didn't feel like a truck and felt more like a wagon.

 

[Charles J Szeman]

I'm curious as to what the resolution to this is going to be. I've had my 2017 Malibu LT since Dec '16. Not quite 10k on it yet, and this issue just started for me about 2 weeks ago. Didn't think much about it and finally decided to check here to see if others were experiencing the same. I've also started noticing that after I've started the car, there is a traffic light shortly I usually stop at. The car seems to 'choke' a little while stopped (provided the auto stop hasn't engaged), as if it wants to go or is having trouble maintaining idle. It's not racing or anything, but enough to notice that it's not smooth. Wonder if this also has something to do with the brake booster. Guess I have a stop at the dealership coming up this week.

 

[GarBec]

Well, I just picked up the Malibu yesterday after it spending 8 days at the dealership service dept. I was assured that it is now repaired. Here is the condensed version:
1 A brake booster kit was installed last month - reserve booster vacuum lost overnight - no improvement
2 Vacuum gauge leak test performed - check valve/vacuum sensor won't hold vacuum - replace part - still lost vacuum
3 Like vehicles in inventory tested - they hold residual vacuum
4 Contacted T.A.C. through dealer case management website - No bulletins or P.I.'s
5 Tested mechanical vacuum pump - only pulled 18 in/hg vacuum; spec calls for 27 in/hg - replace pump assembly
6 Leak test system using smoke test equip and soap solution - leak found at o-ring seal - master cylinder to booster
7 Replace o-ring seal, adding sealer to mating surfaces
8 Perform leak tests again - no leakage found
9 Bleed brakes - test for leaks again - let vehicle sit overnight - vacuum booster now retains residual stored vacuum
10 Vehicle now repaired

I have to commend the tech for his persistence in resolving this issue for me. Too many times a tech or service advisor will use the "could not duplicate problem" rhetoric, and send the customer off.

I believe the root cause of the loss of vacuum was two-fold, one being the check valve/sensor in the vacuum line to the booster didn't hold vacuum, and secondly the o-ring seal between the master cylinder and the brake booster was insufficient to hold vacuum. The mechanical vacuum pump was a surprise piece of the puzzle, but I believe it was not directly related to the loss of residual vacuum in the brake booster. Its function is to supply vacuum when the engine is in turbo boost conditions, when there is no engine vacuum supplied.

Parts used:
1 84038602 booster kit
1 15787976 seal
1 19353126 fluid
1 12662789 vacuum pump

 

[Dale_K]

Thanks for updating the thread. I would make sure to ask for that same mechanic all the time. I might even have a pizza delivered to him at lunch time.

 

[GarBec]

hope they get your issue resolved...on the Equinox...I have read great things about the new Equinox, especially with the 2.0T...please share that experience after your Malibu issues get settled...

Bill

Yes, I think the brake system on the Malibu is now functioning normally: Answering your request for my observations of the 2018 2.0 turbo LT AWD Equinox.

The loaner Equinox I had for 8 days was basically new, had about 1200 miles.
I have a 2016 3.6 LTZ AWD as a comparison
The 2018 is a entirely new platform, weighs 400 pounds less than the prior generation
I was impressed by the acceleration the 2.0 turbo provided, seems quicker than the 301 hp V6 in my 2016
The 9 speed trans upshifts seamlessly, a little harsh when downshifting while coming to a stop
You cannot fool the 2.0 stop/start to stay running at a stop by slowing gently - It stops when the vehicle stops
The controls are very similar to our Malibu's - Features, Apple Car Play & Android Auto
The cabin in the 2018 E-Nox is comfortable but I wouldn't say it is quiet
Handling is acceptable, but not impressive - The ride seems to be slightly harsher than the prior E-Nox
Auto climate control works well
I liked the ability to turn off the AWD - It also has a tow/haul switch
I missed the ability to move the rear seat 8" fore and aft. The 2018 is fixed.
The 2018 is physically smaller - I liked that the prior model was slightly larger

Overall the 2018 E-Nox is a desirable crossover, although personally I still prefer the prior model, mainly because of the available V6, a little quieter cabin, a smoother ride quality, movable rear seat, and physically larger size.
The most impressive attribute is the thrust the 2.0 turbo provides.