Brake pedal

[Toyfrog]

I’ve had this happen a few times with my Mojave after sitting for a few days. I will get in to start it and the break pedal is rock hard. To the point they you really have to put some leg into it to get it to the point that you can start it. It only happens after it sits for a few days, and by a few I mean 2 or 3. Has anyone else had this happen or know what may cause it? Thanks

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[ShadowsPapa]

I’ve had this happen a few times with my Mojave after sitting for a few days. I will get in to start it and the break pedal is rock hard. To the point they you really have to put some leg into it to get it to the point that you can start it. It only happens after it sits for a few days, and by a few I mean 2 or 3. Has anyone else had this happen or know what may cause it? Thanks

Not had it on either of mine (a 2020 I traded for current 2022) but having been around brake systems for decades, it sounds like it's got a leak that allows the vacuum that should be stored in the booster to leak out.
In other words, it sounds like an old system with a bad check valve, or where the engine was off and the brake pedal was pumped several times releasing all of the vacuum stored in the booster.
It should have enough vacuum available after shut-down to pump the pedal 2 or 3 times at least before it loses "boost".
In other words - sounds like a vacuum leak.

I have never tried this before so could be chasing wild water fowl, but I'd be curious as to what happened if:
you did not press the brake pedal but instead pressed the big start button once to get into accessory mode, then again to get into run mode (but not start the engine). I wonder if that would kick on the vacuum boost motor.

 

[Kevin_D]

I’ve had this happen, but it usually takes a couple of weeks to bleed off the vacuum.

Kevin

 

[Jakeyou]

I’ve had this happen a few times with my Mojave after sitting for a few days. I will get in to start it and the break pedal is rock hard. To the point they you really have to put some leg into it to get it to the point that you can start it. It only happens after it sits for a few days, and by a few I mean 2 or 3. Has anyone else had this happen or know what may cause it? Thanks

I have a dodge challenger that I only drive 3 or 4 times a month and it does this every time I drive it.

 

[Skull]

Mine does it after it sits for 2 days every time. No issues with braking operation after start up

 

[Toyfrog]

Not had it on either of mine (a 2020 I traded for current 2022) but having been around brake systems for decades, it sounds like it's got a leak that allows the vacuum that should be stored in the booster to leak out.
In other words, it sounds like an old system with a bad check valve, or where the engine was off and the brake pedal was pumped several times releasing all of the vacuum stored in the booster.
It should have enough vacuum available after shut-down to pump the pedal 2 or 3 times at least before it loses "boost".
In other words - sounds like a vacuum leak.

I have never tried this before so could be chasing wild water fowl, but I'd be curious as to what happened if:
you did not press the brake pedal but instead pressed the big start button once to get into accessory mode, then again to get into run mode (but not start the engine). I wonder if that would kick on the vacuum boost motor.

Thanks for the info, I’ve noticed before that the brakes have felt kinda “ spongy “ compared to my buddy’s Rubi, if I get on the brakes and then let off and pump the pedal a time or 2, they firm up to where I think they should be. This is my first gladiator and also first jeep, drove Taco’s before that, even before they were called taco’s. Please don’t hate me for that comment ?. Guess it’s time for a trip to the dealership and to get the run around and them tell me everything seems fine.

 

[willys 41]

My 2018 had the same issue
I put a vacuum gauge on the hose going to the vacuum booster started it and then plugged the hose going to the motor
It held vacuum over night so the only thing it can be is the booster check valve
I replaced the check valve and no more bleeding down
Its probably the check valve

 

[Outback_Joe]

My 22 bleeds down after about one day. But it starts and breaks great. I have a 30 year old Suzuki that holds vacuum for weeks. Go figure!

 

[ShadowsPapa]

My 2018 had the same issue
I put a vacuum gauge on the hose going to the vacuum booster started it and then plugged the hose going to the motor
It held vacuum over night so the only thing it can be is the booster check valve
I replaced the check valve and no more beading down
Its probably the check valve

That's my gut feeling on it as well. And it's a problem that goes back decades with power brakes. Not totally common in the grand scheme of things, but it's the typical fix for quickly lost vacuum while sitting.

 

[ruscopin]

You aren't alone, it usually takes mine a week before it does it. It caught me off guard the first time because it wouldn't start then I realized I needed to depress the brake more.

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