[EdmJunky]

So I just got this car a little over a week ago, its making this weird noise whenever I start braking coming off some decent momentum. Its like something is sliding forward and hitting metal somewhere, almost sounds like it could be a loose motor mount. Like it slides back when you're driving due to the forward momentum then slides forward and hits the front of the mount when breaking. That's just my guess though. My question is what would be my best course of action here, take it to the dealer to check out or to a certified bmw repair shop?

[Efthreeoh]

Coins in the rear heat ducts is my guess.

[EdmJunky]

Doesn't sound like coins hitting, if it were coins I should be able to here the familiar clatter. It sounds more of like a solid metal hitting another solid metal. I took it to the dealer yesterday and they told me it may be something in the brakes that wasn't put on correctly and is loose (forgot exactly what part he said). Anywho, the mechanic told me it wasn't a motor mount and it didn't seem like anything serious judging from the fact that the car still performs fine. He's fairly certain its going to be something loose in the brakes but said it wasn't an emergency. I have an appointment for next week to have them actually go in and take a look.

[BashShah]

My guess, loose pads.
All brake pads have an inside and outside pad.

The I side pad is held in place by 3 metal prongs.
These prongs are bendable.
My Guess, who ever put them in, bent them too much in.
The key to bending them is the prong can be bend, but the middle of each prong should not.

If not the above, then, caliper bracket is loose or caliper itself.
This is my opinion only...cause it happened to me.
My noise was while braking only.

Tell your mechanic to read this before starting.... Then he can do whatever he wishes to diagnose.

DN

[EdmJunky]

I'll pass on this information to him when it comes time for me to head down there. All in all once they take the wheel off I'd imagine they should be able to spot the issue quickly.

[Three_thirty_I]

Often mechs don't apply proper anti-squeal paste or copper grease to the backs of the new pads and various other parts that require some lubrication, the pads then tend to slide around inside the calliper when braking, especially if you brake going backwards, then when going forwards again. But this should only happen once in each case, and mostly sound like a light thud sound if anything. Hope whatever is loose has not caused any damage!

[TwinTurboRacer]

Upper/Lower control arm bushings? Do you have a vibration at higher speeds? Check for the black fluid leaking out from them.

[BashShah]

Originally Posted by Three_thirty_I

Often mechs don't apply proper anti-squeal paste or copper grease to the backs of the new pads and various other parts that require some lubrication, the pads then tend to slide around inside the calliper when braking, especially if you brake going backwards, then when going forwards again. But this should only happen once in each case, and mostly sound like a light thud sound if anything. Hope whatever is loose has not caused any damage!

1+ and quite brake is a must.
That is some good red Sh!t.

[Efthreeoh]

LOL. I'm not sure what brakes we are talking about here, but pads just don't "slide around" in the caliper on E90 brakes. They can't. The pads sit in channels in the caliper carrier. There is maybe half a millimeter or less between the end of the brake pad backing plate locating tab and the caliper carrier. You apply lube to these areas to prevent noise of the two surfaces rubbing each other and causing a high-frequency squeal, not banging into each other. When you refurb the brakes, the brake dust gets caked on the pad backing plate so heavily that you have to literally pry the pads out of the caliper carrier.

OP, no mechanic would let a car out of his shop with "something loose in the brakes." You can't assemble the brakes any other way than the correct way, the parts will not fit otherwise (okay maybe you could put the pads in with the backing plates facing the rotor on the non-piston side, but in the first application of the brakes you'd hear an awful grinding noise). The brake is held to the hub by 4 bolts. Two bolts ((6) - in the drawing) hold the caliper carrier (3) (where the pads (4) sit) to the hub and are torqued to around 60+ ft/lb. The other two bolts (9) are the caliper guide pins that hold the caliper (1) to the caliper carrier, which are torqued to around 30 ft/lb. The mechanic could have inspected the torque on these bolts in under 3 minutes.

Here's a pic of what the brake is comprised of just so you have a better familiarization with the parts.

[EdmJunky]

I see what you're saying. I was just going off of what the mechanic at bmw told me because frankly I don't know enough about these cars to get in there and troubleshoot myself. They didn't actually look at anything either, he just got in the car with me and listened to the noise. Would you suggest I take the car elsewhere and have them take a look? I imagine if something really is loose in there they'd be able to spot it quickly so I don't expect it to be very expensive. On the contrary if I go to the dealer that's an easy $200 minimum.

[Three_thirty_I]

Mine had this minor and slight knock sound from the lack of copper grease on the backs of the brake pads after the dealer replaced them. They didn't even bother to clean anything from the looks of it. This knock sound would only typically be heard when moving the car back and then after going forward again and braking, or when braking while reversing etc. After stripping the brakes, cleaning, and then applying copper grease where needed all was fine and has remained so. There is very little play in the calliper, but there is often still enough to cause this.

[BashShah]

Efthreeoh, beleive it or not.

Bought some Akebone Pads.
damn inside pad on front left was not going in, so I bent it in to help it.

after lower the car and driving around, I hear a Clak, Clak, Clak, as I brake semi hard.
was not trying to bed them.....this may not be the OP's issue, but thought don't leave a stone un-turned.

finally decided to take it to a a friend's shop and 2 hours there, and we are still scratching our heads.....then I told him, just pull the inside pad and see it is too loose and to see if it can be inserted more snug.

and bang....problem gone.

PS: I agree with everything you said.....you are one of my heroes on this forum.
thanks for all.

Also OP, you BMW is not taking the time to investigate it, then either escalate it...or find another Indy shop.

DN

[Efthreeoh]

Originally Posted by DarkNemesis

Efthreeoh, beleive it or not.

Bought some Akebone Pads.
damn inside pad on front left was not going in, so I bent it in to help it.

after lower the car and driving around, I hear a Clak, Clak, Clak, as I brake semi hard.
was not trying to bed them.....this may not be the OP's issue, but thought don't leave a stone un-turned.

finally decided to take it to a a friend's shop and 2 hours there, and we are still scratching our heads.....then I told him, just pull the inside pad and see it is too loose and to see if it can be inserted more snug.

and bang....problem gone.

PS: I agree with everything you said.....you are one of my heroes on this forum.
thanks for all.

Also OP, you BMW is not taking the time to investigate it, then either escalate it...or find another Indy shop.

DN

No intention to flame what you said, but unless the parts are incorrectly manufactured, I just can't see where the pads would sit so loosely in the caliper bracket as to make such a loud thunking noise as the OP describes. Now I'll admist I've never tried to install brake parts incorrectly, but I just don't see how you can assemble a brake incorrectly and if you can, that it'd not immediately be apparent and inoperable. But I guess anything can happen. The only thing I can think of is if the pad material separated from the backing plate (just thought of this), but usually when that happens the pad falls apart rather quickly.

I agree with you, the BMW mechanic should have resolved the issue right there by at least saying he inspect the brakes and found no faults and the OP should go elsewear.

[tony20009]

Originally Posted by samfb24

So I just got this car a little over a week ago, its making this weird noise whenever I start braking coming off some decent momentum. Its like something is sliding forward and hitting metal somewhere, almost sounds like it could be a loose motor mount. Like it slides back when you're driving due to the forward momentum then slides forward and hits the front of the mount when breaking. That's just my guess though. My question is what would be my best course of action here, take it to the dealer to check out or to a certified bmw repair shop?

You should be able to get accurate information as well as quality repair work from both. I can guarantee you the dealer will not be the cheaper of the two. I can't promise, however, that the certified repair shop won't cost just as much.

I suggest you go to one and then the other, asking for a quote from each one. Then you'll know which is the better option for you. Unfortunately, you'll probably have to pay two diagnostic fees, one of which will be money gone for good as it won't be applicable to any actual repair work.

All the best.

[EdmJunky]

Yeah, I will be looking for a local bmw shop near me. Ive gotten crappy customer service from that same dealership on several occasions now and from different people so I don't even think I'll be showing up for my appointment with them. I'm pretty sure this is going to be a simple issue, I just need someone to get in there a take a look. and now I have another issue with the tail lights, I bought this car thinking all was dandy and I wouldn't have to go through headaches like this, ah well. At least nothing extremely serious has risen so I guess I should be thankful for that.

[BashShah]

Originally Posted by samfb24

Yeah, I will be looking for a local bmw shop near me. Ive gotten crappy customer service from that same dealership on several occasions now and from different people so I don't even think I'll be showing up for my appointment with them. I'm pretty sure this is going to be a simple issue, I just need someone to get in there a take a look. and now I have another issue with the tail lights, I bought this car thinking all was dandy and I wouldn't have to go through headaches like this, ah well. At least nothing extremely serious has risen so I guess I should be thankful for that.

Then go to any reputable shop.
Brakes are not rocket science.

If they specialize in wheel alignment also, then that would be the best as they may check suspension also.

DN

[EdmJunky]

Originally Posted by DarkNemesis

Then go to any reputable shop.
Brakes are not rocket science.

If they specialize in wheel alignment also, then that would be the best as they may check suspension also.

DN

Yeah I'll have to do that. I may just pop the wheel off myself and wiggle some things around to see if I can find the source of the noise myself.