Engine noise after hard braking

[andreyiv]

Hey guys. Recently I have noticed that after I brake hard, I hear this noise that is coming from the engine. It sounds like a pulley is turning but the belt it is supposed to be turning is not rotating. It mostly happens during spirited driving when I brake too hard or when I turn while braking. I can kinda feel it through the steering wheel and it changes pitch as I turn the wheel. I can hear it very good at idle and it goes away after about 1.5k rpm and comes back as the rpm come down. After a while it goes away and everything is fine until I brake hard again. The only thing that comes to mind is maybe the power steering belt/pump but I don't know how it is connected with the brakes. Anyone has any ideas at all?
Thanks in advance. I really appreciate your help guys.

 

[mjbst111]

hard braking.... maybe the braking slows the engine faster than the power steering pump wants to slow down and makes the power steering belt squeak.

I guess I would check the power steering pump belt.... why not

 

[andreyiv]

That is a good idea and I now see how it is connected to steering. I'll try hard braking in neutral tomorrow and see how it goes. I never thought of that perspective, thanks. And maybe it continues to do so until the belt corrects itself (usually around 5-10 minutes). After this happened today, I got home and shut off the engine (still with the noise at certain rpms). After about an hour, I got in the car again and the noise was gone. Thanks again mjbst111. Anyone else has any ideas at all?

 

[Kirby]

Is there any chance that the braking stresses are changing the position of the engine or body components, and something is rubbing a pulley or belt? Look in areas where the pulleys and belts are close to body parts and see if there are any telltale marks.

Volvo used liquid filled motor mounts. If they failed (which eventually they all do) the engine dropped about an inch. Then under heavy stress the fan would sometimes scrape the fan shroud.

 

[andreyiv]

Today I tried braking hard in neutral and the noise still occured. I didn't check under the hood because it was snowing and very windy today so I'll try to do that sometime soon. I noticed that the noise is usually there above 1k rpm and below 1.5k rpm. It's in that specific range and it sounds wierd, I can't explain in exactly. I think it is coming from the left (driver) side but I'm not sure. It maybe closer to a sound a powerful electric motor makes (the buzzing kinda sound) when it can't turn over at normal speed. It's like something is turning at a very slow speed, maybe slower than 1 rotation per second. I am pretty sure it's power steering but I can't connect that to hard braking (the noise is louder if the wheel is turned while braking) in neutral with constant engine rpms especially when it goes away slowly and not right after. Anyone has any clue to what it could be? I am despirate, kinda short on money now so I don't feel like running to a mechanic and getting ripped off.

 

[Tim328]

I have the same noise on my 328i. My thought was that its something to do with the anti-lock brakes. My noise sounds like it comes from the drivers side front. But it comes and goes as yours does.

 

[epj3]

Hmm, could be the ABS... but doesnt the traction control light come on when ABS comes on?

 

[Wadula]

nope. abs works without the light.

i have no idea what that sound is. maybe i canb try tomorow while driving and listen carefully. if i know that sound (in case i have/hear it) i mightbe able to determine what it is

 

[Ghost]

How many miles on your car? Is the noise only happening when you’re moving? If it does, and it’s worse while turning, it may be your wheel bearings depending on the miles, (right turn-bad left bearing, left turn-bad right bearing) especially if you feel it through the wheel. I suggest you make sure your power steering fluid is full, spray some WD-40 on your belts, see if the problem persists and go from there.

 

[bmwperson]

I thought you`re not supose to put WD40 on rubber/plasic stuff... but then I might be wrong, As for the bearing, the noice would get louder and louder as the speed would increase I think, at least mine does that, you cant hear it when Im driving below 60, 80 somewhat you can hear it, 120 you can hear it really good...

--
Tom

 

[andreyiv]

The noise is there even if the car is stationary but while turning the wheel (like during parking) and it is not affected by speed at all. The peak of it is at about 1.2k rpm and it goes away after about 1.3k rpm depending on how hard the braking was. Wadula, to achieve this, try braking really hard and move the wheel left and right like you are trying to avoid an accident or something. That is the easiest way for me to get it. To hear it, all you do is turn your radio down and just do what I have described. It is pretty wierd, it most likely has something to do with power steering but I have no clue how engine rpm affects it so much. No noise below 1k and no noise above 1.3k. The range gets bigger in proportion to the amount of braking and so does the time it takes for the problem to go away. Thanks for all your replies guys, really appreciate it.

 

[epj3]

Could be tire noise.

 

[bmwperson]

I dont think its the power steering pump but try this, while standing still rev up to 1-1.3 rpm and turn your wheel right and left and see if you get the noice, if the pump is bad then you should hear it... I was thinking that it could be that the pump is leaking and goesnt generate enuf pressure if its below a certain rpm, but that wouldnt fit well with your descriptio... just a thought...

Try what epj3 said, rotate the tires around... it doesnt cost anything to check...


--
Tom

 

[andreyiv]

It's not tire noise because I get the same noise while standing still and not turning the wheel at all. I've listened to the noise today very careful while in the drive way and I can't describe it at all. Kinda close to what a pump would sound like when it's pumpimg but the exit is clogged, sometimes I hear this sound that is close to water spraying out of a small hole under pressure. Before I did see some sort of fluid (looked kinda like tranny fluid so it could be power steering) on some parts of the steering assembly underneath the car. Maybe something has clogged the fluid passageway and caused a leak but I have no clue how that is connected to hard breaking unless the thing that is blocking the way moves forward after braking hard, but then again, it doesn't help if I floor it. Oh, I saw that liquid when I was replacing the 02 sensor at the mechanic and we tried to figure out where all that came from, we tried everything you can do with a car that is not in motion but had no luck. I'll try to get underneath the car and see if the liquid is back or not. Almost forgot, the odometer just hit 100k a few days ago. Thanks again guys for all the recomendations and thanks for staying with me even though this seems impossible.

 

[andreyiv]

Yesterday, I've tried the following. Raised the engine rpm until I don't hear any noise, then turn the wheel and as soon as it moved an inch, the noise was right there and the rpm fluctuated. So this tells me it's the pump? Thanks.

 

[epj3]

Add power steering fluid, my car has a very small leak in the hose and when the fluid gets low it makes weird noises.


By the way -- I believe you need to add Dexron-II ATF fluid to your power steering system.

I'm pretty sure this will take the sound away then.

 

[andreyiv]

Cool, thanks a lot Eric. Sorry I haven't been on for a while, just moved and hand't had internet access for a while. Thanks to all, really appreciate, will tell how it goes.

 

[it7eke2000]

I have this same problem on my 1995 M3. Whenever I brake hard I hear a "electric toy car" grindy/not right noise in the lower rpms when i begin to rev engine and a vibrating in the floor/wheel. I was wondering if you found out for sure what the problem was yet? b/c one BMW guy told me it was the idler valve (i doubt thats right) and wanted to charge $500 to fix (that is a totally exagerated price, and im pretty sure he thought I was stupid and tried to suck a buck or two outa me)