Whine from rear wheels when braking...

ihadablackdog · Post by **ihadablackdog** » Sat Mar 17, 2018 10:29 pm

Today I collected my "new to me" (2011) Z4. I had a Z4 in 2012 (was a member on here back then with a different username) but due to circumstances had to let it go, and this is the first chance I had to buy another.

So, driving home from the dealer I notice that when braking, it sounds something like an electric car regen, also similar to when you hear a policecar/ambulance siren in the distance. It seems to be from the rear wheels.

It only happens when braking, not coasting etc, and no noise when driving.

Cant remember this from my old car.....is this a problem or meant to be?

Mad Professor · Post by **Mad Professor** » Sun Mar 18, 2018 2:14 pm

Sling it back at the dealer and tell them to sort it out asap
Maybe discs/pads need replacing ?

ph001 · Post by **ph001** » Sun Mar 18, 2018 2:33 pm

Sorry to state the obvious but does it in fact have regen braking option fitted?

ihadablackdog · Post by **ihadablackdog** » Sun Mar 18, 2018 4:06 pm

Have to be my local dealer (Devon), got it from a dealer in Hampshire (saw it on the internet). (it is a BMW dealer, with AUC warranty).

Regen option on a 2011 e89 Z4? Didn't know there was such a thing, hence asking on here...

I'll email the original dealer and see if they have any advice, but think it will be going to the local one soon.

Never had an AUC BMW that hasn't had some problems...despite this one going through a 140 point check! (call me cynical, but do those things actually exist...or get done). I think its "car has an issue, fix it before collection and it comes out of our profit...let the customer do it after collection and its a warranty job"...

Lazza · Post by **Lazza** » Sun Mar 18, 2018 6:38 pm

Not sure but I think they do away with an alternator and recharge the battery using regen. No idea how that works! I’ve never heard anything like that on mine though.
Could just be that it hasn’t been used for a while and the discs are a bit corroded, in which case it should clear up after a bit of use.

Smartbear · Post by **Smartbear** » Sun Mar 18, 2018 6:45 pm

Lazza wrote: ↑Sun Mar 18, 2018 6:38 pm Not sure but I think they do away with an alternator and recharge the battery using regen. No idea how that works! I’ve never heard anything like that on mine though.
Could just be that it hasn’t been used for a while and the discs are a bit corroded, in which case it should clear up after a bit of use.

They definitely have an alternator, it’s a bit misleading as I think the regen is just the alternator “switching in” a higher rate of charge when the brakes are used & there's no actual charging mechanism connected to the brakes themselves

Rob

ihadablackdog · Post by **ihadablackdog** » Sun Mar 18, 2018 7:23 pm

I thought it might be due to non use, I think its been sat in the dealer for at least 2 weeks.

However, after a 150 mile drive home it still does it.

Blimin' snow today means no fun in my new toy!!!

I've emailed the salesman asking if it was road tested and what the mechanic has to say (but I doubt he'll reply)...if its no better next week I'll book it into my local dealer and see what they find.

ph001 · Post by **ph001** » Sun Mar 18, 2018 8:33 pm

Yeh the regen thing just disconnects the alternator when accelerating (meaning it only recharges the battery on coasting and braking), I’m just wondering if it’s belt noise you can hear. Would obviously be coming from the engine area though, not the back.

ihadablackdog · Post by **ihadablackdog** » Mon Mar 19, 2018 10:45 pm

I didn't mean to imply its a problem with "regen"...I simply used that phrase as it seemed appropriate.

I'm going to book it into my local dealer for investigation. I might ask them to give the whole car the "once" over, to make sure everything is ok to begin with. Would they charge a lot for this?

Any problems they find that are warranty items they can fix, or if there are problems that aren't warranty items (i.e. low brake pads/discs) then I can go back to the supplying dealer. I'm not expecting any of those sorts of issues though.

Might ask for an oil change as well...service book says it was last done January 2016...car has only done 10k miles since, but its every 2 years right?

Haven't checked the indicators in the car yet, and guess the oil change indicator would be on, so perhaps they did that before I collected it, although they haven't stamped the book. I'd rather be safe than sorry.

ihadablackdog · Post by **ihadablackdog** » Tue Mar 20, 2018 9:44 pm

So I phoned the selling dealership today and spoke to the salesman who sold me the car. I asked if he had any answers to my email (was it road tested and did he have any opinion on what the noise might be).

He said it would've been road-tested. He then checked his "system" and told me the car had new pads & discs front and rear and that it might be those bedding in.

I was quite pleased to hear its had new brakes all round! Might be placebo effect, but the noise didn't seem *quite* as much on the way home.

So I went to my local dealer to ask if they could check it out, and give the car a visual check over to spot if anything needs doing, and also confirm new brake pads/disks etc.

They also scanned the key for service details. Said the service history looks about right, one oil change a few months late, but if they've just done it when prepping the car, then thats fine (although the service booklet not stamped).

So its going in on Saturday. They said there wouldn't be a charge unless they find problems etc, and in that case will talk to me.

Getting more used to the clutch and driving a petrol (last car was Diesel), so driving a bit more smoothly now.

If only I could get rid of the pot holes....these alloys and hard suspension are horrible!

ihadablackdog · Post by **ihadablackdog** » Mon Mar 26, 2018 7:29 pm

Quick update to the noise situation....

Turns out there is a problem.

Can't say any more at the moment cos I'm talking to the selling dealer to sort it out, but will give them time to sort it and then update you.

Will also be able to give an opinion on their after sales service.

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