[GarBec]

@Autobiz Definitely replacing the aux pump will fix if it is broken but most of the posts in this discussion are about loss of vacuum after the car sits off causing a hard brake pedal when starting. No codes present nor running erratic as your video states. Several with the hard brake pedal have even had the aux pump replaced as well as the booster and seals with no improvement for that particular issue. It certainly could help some but it isn't a "for sure" as some have already tried that.

Yes, our 2017, 1.5, LT Malibu had been serviced three times to attempt to correct the hard pedal - loss of residual storage of vacuum. It has had all of the brake booster components replaced, lines, check valve, booster assembly, o-ring, vacuum pump, smoke test, etc. This was when it was essentially brand new; fast forward to today, it has about 30,000 miles and the problem with the hard brake pedal after setting idle for a day or so still exists.

The dealers' conclusion was that all of the ones in their inventory did the same thing, so it must be normal. I didn't like the analysis, but was frustrated about how many times the repair was attempted and replacing all of the related components failed to correct the issue.

This isn't a safety related issue; just an inconvenience when getting in to start the vehicle after its not been run for a while. I just live with the issue as its not that important; it's just not right in my opinion. The vehicle has normal braking performance, and does retain residual booster vacuum after turning it off for many hours; just not overnight or a few days after the last running.

My personal diagnosis is that I believe that the link that goes between the pedal assembly and the master cylinder may be just a bit too long; I say this because there is no free play in the pedal before braking occurs; it's like the pedal is being partially depressed all of the time. If this is so, the booster may leak vacuum internally because the booster valve is being slightly depressed even without touching the brake pedal.

I gave up trying to get anyone to pursue this possibility and just drive the car; well, the Wife drives the car. I seldom get in it anymore.

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[RcClockman]

This is not Normal... Mine is doing the same thing now...I had the Brake Booster changed out under warranty back in December for the common Sqeeking of the pedel when you push it, and the fix is to replcace the Brake booster...In fact my brother has had his changed out 3 times for that on his 2017 malibu, and when it did it for the 4th time, GM bough his car back,,, There is definatly a problem with these brake boosters, whether its the annoying Sqeek when pressing down the pedel or the Hard pedal at start-up, this is not normal,,,,Mine is doing it every morning now,,,Since i had it replaced last Dec, its should be replaced under the 1 year Parts warranty, even though im now out of my Bumper to bumper warranty...

 

[campb292]

I had my booster replaced twice for the squeaking noise when pressing and releasing the brake pedal. They then replaced with a new part number I only see linked with the Impala and fine since. It's the seal that squeaks so they always replace the whole booster because the booster and seal is all one part.

As for the hard brake pedal, that one I don't deal with but several forum members have.