Hard Brake Peddle/Won't start

[1Seekingzen]

I've owned a 2024 Gladiator Mojave for a while now and have been dealing with a strange issue that neither two dealerships nor an independent shop have been able to diagnose. Occasionally, after the Jeep sits overnight, the brake pedal becomes extremely stiff when I try to start it. It’s not all the way to the floor, but it takes nearly all my strength to press it down far enough to start the vehicle. Most of the time, though, the brake feels soft and depresses easily, allowing the Jeep to start without issue.

The independent shop bleed the brakes to rule out air in the system, but that didn’t solve the problem. The dealerships haven’t been able to replicate the issue and have no idea what’s causing it. Compared to my wife's 2023 Wrangler Rubicon, the brakes on my Gladiator feel weak overall.

I suspect it might be related to the vacuum assist system, but both dealerships have dismissed that idea. Any thoughts?

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[Lost1wing]

I think you have a vacuum leak start at the booster.

https://www.moparoempartsdirect.com...s&utm_term=2336324770923977&utm_content=Mopar

 

[Lost1wing]

I think you have a vacuum leak start at the booster.

https://www.moparoempartsdirect.com/oem-parts/mopar-brake-booster-check-valve-68053596aa?origin=pla&msclkid=95dfecfe186b17492f4884647332a95f&utm_source=bing&utm_medium=cpc&utm_campaign=Perf Max | Mopar | Parts&utm_term=2336324770923977&utm_content=Mopar

If this valve has a leak, it could cause your booster to lose it's vacuum.

 

[1Seekingzen]

I think you have a vacuum leak. Start at the booster.

That was my exact thought. I just called Jeep Customer Care who told me to open a case it has to be in the dealerships possession. I just picked it up today, they had it nearly a week. I called the dealership, who asked why I would being it back, they found nothing. I’m getting a little upset!

 

[Lost1wing]

If this valve has a leak, it could cause your booster to lose it's vacuum.

That was my exact thought. I just called Jeep Customer Care who told me to open a case it has to be in the dealerships possession. I just picked it up today, they had it nearly a week. I called the dealership, who asked why I would being it back, they found nothing. I’m getting a little upset!

To rule out this being the issue, if you see your brake lights come on, this is not your starting issue. Same switch is used. So if you cannot depress the pedal enough to activate the brake lights, this will be your problem.

 

[Janster]

When mine sits overnight…there are days when the pedal is stiff’ and doesn’t depress much or at all and there are other days where its soft and goes down farther.

I’ve never had any issues with it not starting.

To those smarter than myself…
What detects the pedal is depressed ? Is there a sensor?
Or does it read the actual vacuum pressure to allow it to start?

 

[Lost1wing]

When mine sits overnight…there are days when the pedal is stiff’ and doesn’t depress much or at all and there are other days where its soft and goes down farther.

I’ve never had any issues with it not starting.

To those smarter than myself…
What detects the pedal is depressed ? Is there a sensor?
Or does it read the actual vacuum pressure to allow it to start?

Brake pedal switch. The problem is when the booster is flat ( no vacuum), the pedal is very hard to depress, enough that you can not activate the switch. No start, no brake lights.

 

[Lost1wing]

I'm not positive, but most brake pedal switches are depressed with the brake off. When you depress on the pedal the switch is relaxed, and now completing the brake/starter circuit.

 

[Lost1wing]

I had a quick thought of another test you could do. If you can remote start it, it would also be a clue that it it related to the brake pedal.

 

[Hunter#1]

Once in awhile my brake pedal is stiff, but truck always starts. Also no brake problems

 

[Lost1wing]

Once in awhile my brake pedal is stiff, but truck always starts. Also no brake problems

You may just be able to press the pedal further. You wouldn't have any brake broblems with a small vacuum leak while operating. It's only after the vehicle is off for an extended time and the vacuum is gone.

 

[SamJ3]

This is not an uncommon issue. My 2022 JT Sport has similar behavior when sitting for more than a few days. Here is what happens.

State: There is a very slight vacuum leak either in the vacuum booster, the check valve grommet , or the check valve at the port where the vacuum is supplied to the booster. This bleed off is small, so it takes some time to loose enough vacuum to empty the reservoir.

Condition: If the booster has lost all or nearly all of it's vacuum (that is, the pressure inside the booster's reservoir is approximately equal to atmospheric pressure), the booster cannot assist in applying pressure on the master cylinder.

Complication: When the booster can no longer 'boost', all of the force needed to actuate the master cylinder, i.e., depress the brake pedal, must be provided by the driver.

Starting logic: The brake pedal must be applied to allow the starter to operate. This is detected by the brake light switch. The pedal must be depressed far enough for the brake lights to illuminate.

Immediate Resolution: Press the brake far enough for the vehicle to recognize the foot brake is applied. When there is no boost, that will take much more effort than normal. The pedal does not need to be floored, but it must move far enough to simulate applying the brake. Also, once started, let the engine run for enough time to recharge the brake booster - about 10-15 seconds. The vacuum is supplied by a combination of engine vacuum and a vacuum booster pump.

Permanent resolution: resolve the slow leak by addressing the source. However, doing this under warranty may take a lot of patience and convincing - even the service manual tests seem to allow a small degree of pressure loss before declaring it a problem. Outside of warranty, the most likely source of the problem is the check valve, which costs $60-80. (The booster is much more cost, and much more labor to replace.) For me (and many others), it is not worth the hassle or cost of repair, as it doesn't affect driving.

Summary: Most likely, when the brake pedal is hard and you can't start the engine, you just need to press harder on the brake pedal.

(If the booster does not recover after starting the engine, or you experience loss of boost while driving, then the problem is elsewhere in the power brake boost system.)

 

[Badunit]

I know it isn't just or right but sometimes it is better to fix it yourself at your own cost versus arguing with dealer service and spending your time taking it there and picking it back up and all you get is "no problem found" or a "repair" that didn't fix the problem. Replacing the valve is a $60 gamble but it could be a gamble you're willing to take.

Mine did this same thing a few times when new. I haven't had it happen recently.

 

[Gatorized]

not sure if there is an adjustment or not, but maybe the brake switch is too close to the pedal and needs to be moved so less pressure is needed to activate the brakes thereby allowing the starter to engage.

 

[twbranch]

Sorry to restart this thread but, what if the brake is stiff and the remote start does not work? Has anyone had this problem?

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