Braking - is this expected behaviour?

[Ted H]

Hi all.

I took delivery of a new 73 plate Mercedes EQC at the end of last year. Within a couple of weeks, an issue with the brakes became apparent.

When I press the brake pedal, sometimes - about 25% of the time - as the car slows and I press the brakes, the pedal will suddenly lose tension and I get a grinding noise/ grinding feeling through the pedal for a couple of seconds before it reverts to normal feeling/noise. During this couple of seconds, the car does not brake. I’m 99.9% sure this is not ABS, and it only happens at low speeds, around 15mph.

The brakes also appear to “seize up” - not sure if this is the right description - quickly, like when you’ve not driven a car in a couple of weeks and you move off for the first time, you get that thump noise and feeling as the discs unstick. I’m getting this when the car has been parked up for only a few hours, never mind a couple of weeks.

The main dealer tells me this is all due to corrosion. However, the car is driven several times per day, every day, and I wouldn’t expect this outcome.

So my question is…is this sctualpy corrosion and to be expected? I’ve had several EVs before this and while the brakes are used less frequently than an ICE car, I haven’t seen such behaviour on the BMW, Audi or the Tesla EVs I’ve had.

Thanks
Ted

[E-bmw]

I am guessing that you don't work on your own cars & it has a warranty.

That being the case the ONLY cause of action is to take it back & get them to fix it properly rather than fob you off with bullsh!t.

Be firm & polite about it but remember IT IS BRAKES! and they may just be the last line of defence for you & your loved ones.

[Ted H]

Yep, warranty all the way with this one. I do minor work to my cars but I don’t mess around with brakes.

When you say fix it properly, do you have any thoughts on what may need to be fixed/replaced/changed in this instance? My first thought was if the discs are corroding so quickly, it needs different discs, but this is a guess from a place of limited knowledge.

[GreenV8S]

Ted H said:

do you have any thoughts on what may need to be fixed/replaced/changed in this instance?

That's their problem, not yours. Under no circumstances should you try to advise them what you think the problem might be or what you think they might need to do to fix it. That path can potentially leave YOU responsible for any time spent or costs incurred following your instructions. The only thing you should be telling them is the symptoms, and which of your rights you're asserting to get it fixed. Be aware that their main strategy will be to fob you off and hope that your rights under the Consumer Rights Act expire before you invoke them. If the problem can be reproduced easily it will help your case if you take one of their people for a drive around the block and get them to agree there is a problem. Othewise they can waste days or weeks claiming that they can't see anything wrong.

Also read up on the Consumer Rights Act 2015 to understand what rights you have now and how these rights gradually disappear the longer the problem is unresolved.

[Maxdecel]

Ted H said:

Hi all. ....When I press the brake pedal, sometimes - about 25% of the time - as the car slows and I press the brakes, the pedal will suddenly lose tension and I get a grinding noise/ grinding feeling through the pedal for a couple of seconds before it reverts to normal feeling/noise. During this couple of seconds, the car does not brake. I’m 99.9% sure this is not ABS, and it only happens at low speeds, around 15mph.

........... thump noise and feeling as the discs unstick. I’m getting this when the car has been parked up for only a few hours, never mind a couple of weeks. The main dealer tells me this is all due to corrosion. However, the car is driven several times per day, every day, and I wouldn’t expect this outcome.

So my question is…is this sctualpy corrosion and to be expected? I’ve had several EVs before this and while the brakes are used less frequently than an ICE car, I haven’t seen such behaviour on the BMW, Audi or the Tesla EVs I’ve had.
Thanks Ted

Para #1 - Inconsistent pedal feel would appear to be a "thing" ! Search it, I know nothing about the car but brief look and it might be connected to regen and/or an automonomous feature.
Grinding noise ? Wouldn't imagine that's a feature that meets the spec of the car?
No deceleration .. Are you sure ? That certainly won't meet the design spec. and should sound alarm bells ringing with your service advisor !
Par #2 - They're BS'ing you, given the use you describe and assuming you use the brakes , NOT Regen continually. Is this auto hold ? It may be the shoes releasing (assuming it's drum in hat design) You'll need someone who's familiar with the car to compare.

Par #3 - Very much doubt it, that's a good example of crap customer service never mind ignoring a potential safety issue.
Here - https://www.mbeqclub.com/threads/variable-brake-fe...

[Panamax]

Disc rusting in a short space of time and resulting pad movement is 100% normal.

ABS cannot create braking force when there's no friction available for the tyres. This can feel like "no brakes".

Mercedes brakes are at least partly active. The system reacts not only to how hard you push the pedal but also to how quickly you hit the pedal. The driver experiences this as an "inconsistent" brake pedal.

[Caddyshack]

I had an E AMG55, it had an ABC brake pump and that used to vibrate and make odd noises, it was replaced under warranty and was common…that was a 53 car so a while ago

[Ted H]

Thanks all for the input and guidance.

Maxdecel said:

Para #1 - Inconsistent pedal feel would appear to be a "thing" ! Search it, I know nothing about the car but brief look and it might be connected to regen and/or an automonomous feature.
Grinding noise ? Wouldn't imagine that's a feature that meets the spec of the car?
No deceleration .. Are you sure ? That certainly won't meet the design spec. and should sound alarm bells ringing with your service advisor !
Par #2 - They're BS'ing you, given the use you describe and assuming you use the brakes , NOT Regen continually. Is this auto hold ? It may be the shoes releasing (assuming it's drum in hat design) You'll need someone who's familiar with the car to compare.

Par #3 - Very much doubt it, that's a good example of crap customer service never mind ignoring a potential safety issue.
Here - https://www.mbeqclub.com/threads/variable-brake-fe...

Thanks for the info -the link you shared makes for interesting reading. Several others with the exact issues I have, so it's good to see it isn't an isolated problem.

I do use both the brakes and regen, it seems to be when regen is on that the weird brake pedal feelings and noises kick in. and yeah, it is the auto hold/handbrake which is making the thump noise. I've had this on every car I've had....but usually after it's been parked for a week and not for 2-3 hours like the EQC.

Yes I think the service people are taking the mick tbh. They have been generally unhelpful and difficult from the point I booked the initial appointment through until collection, and not just with the braking issue. I may try another dealership to see if I can get better results.

The safety issue is the biggest concern. I will follow up with the leasing company tomorrow as ultimately it is their car, and they either need to guarantee the safe operation or take the car back and cancel the agreement.

Panamax said:

Disc rusting in a short space of time and resulting pad movement is 100% normal.

ABS cannot create braking force when there's no friction available for the tyres. This can feel like "no brakes".

Mercedes brakes are at least partly active. The system reacts not only to how hard you push the pedal but also to how quickly you hit the pedal. The driver experiences this as an "inconsistent" brake pedal.

Thanks, will take this under advisement.

[Ted H]

Caddyshack said:

I had an E AMG55, it had an ABC brake pump and that used to vibrate and make odd noises, it was replaced under warranty and was common…that was a 53 car so a while ago

It's good they sorted that, an E55 needs reliable brakes to be driven properly I have seen similar stories from the C class range too, so may be a known, albeit uncommon, issue.