Brake Pedal Pressure Changes -- Thoughts?

Chedman13

Chedman13

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Location
Illinois
Car
2014 Mercedes-Benz GL63 4Matic
I need some help diagnosing an issue with my brakes. This has happened every once in a while, and seems more frequent in colder weather.

When I press down on the brake pedal typically, it is even pressure to complete stop.

Sometimes, I press down and the brake pedal is extremely firm and hard to push down. Initial bite is bad and I have to really press much harder to get the car to complete stop.

I've had this issue since day 1 of the car, with or without the AP Racing Calipers (5.1 DOT fluid, stainless steel brake lines).

My guess is possibly the "brake assist" feature, pre-pressurizing the brakes (I find this happen more under raining/snowing situations where the laser cruise won't work due to the interference) or an issue with the brake cylinder.

Anyone else have this experience?
 
I've noticed that when pressing down quickly on the pedal, it will grab much sooner. Normally I can press it to the floor, but it is much shorter of a distance when braking quickly. Same thing as you mentioned, but do you have the issue when braking normally also?
 
StuLax18 said:
I've noticed that when pressing down quickly on the pedal, it will grab much sooner. Normally I can press it to the floor, but it is much shorter of a distance when braking quickly. Same thing as you mentioned, but do you have the issue when braking normally also?
Click to expand...

Yes, definitely happens more at quick braking, but still sometimes at normal braking.

Interesting to here someone else have this issue.

---------- Post added at 07:11 PM ---------- Previous post was at 07:04 PM ----------
GJBenn85 said:
Does it tend to happen after driving a while? I suspect it has to do with the pads being hot/cold, as they tend to "bite" sooner when warmed up vs. cold.
Click to expand...

I did think of this, but definitely ruled this out. It's pedal pressure vs bite.
 
Same thing with mine on fast braking. I had one emergency brake where I locked up the rear for a split second. It was unmistakeable though, pedal was hard and firm and pretty much at the top during this procedure. The rear also stepped out for the split second of lockup that occured.
 
SexualChocolate said:
Same thing with mine on fast braking. I had one emergency brake where I locked up the rear for a split second. It was unmistakeable though, pedal was hard and firm and pretty much at the top during this procedure. The rear also stepped out for the split second of lockup that occured.
Click to expand...

This is an exact example of the scenario, thanks for sharing. I found this online. I wonder if it's the design of the brakes since it seems prevalent in other Infiniti's. I ruled out brake line obstruction (fluid and line) so if it's not the vacuum issue, I'm guessing just design...

Brake Pedal Too Firm. If you step on the brake pedal and all of a sudden it feels like you're doing leg presses at the gym with a new personal trainer, your brake pedal may be too firm. This symptom points to a few potential problems, all of which need to be fixed as soon as possible.

  • Vacuum Problems: Your brakes are easier to press because of a brake booster that gives your foot the strength of 10 men. This booster uses vacuum to help you activate the brakes. If there is a vacuum leak somewhere in the system, it won't have enough negative pressure to do its job. Check the vacuum system for leaks. If you find none, your brake booster is probably bad and will need to be replaced. This can be tested by a shop if you want to be sure.
  • Brake Line Obstruction: It's possible for something to block brake fluid from reaching a portion of the system. This could be something in the line like a chunk of rust, or it could be a pinched brake line. Visually inspect the brake lines and replace damaged brake lines as needed.
 
So this may signify an issue and isn't just a built in feature? I always thought it was to help brake faster during "panic braking" because there's less lag time between you stepping on the pedal and the brakes actually grabbing. :confused:
 
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