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Strange Sound Under Car

3K views 16 replies 9 participants last post by  325is1994 
#1 ·
Hi!
i noticed a sound that really drives me nutz!

with radio off only (not that the sound diseappear but it's not very loud).

It's a sound that come every 2 or 3 seconds, always! It's a little "knock". Sound is still present when parked with engine on. Comes from under my feet, I can "feel" it if I have the feet on the brake pedal. If i don't have feet on pedal, i still hear it.

it's like: Toc (3 seconds) Toc (3 seconds) Toc (.....)...

That so weird??!! I get that sound when i drive, when I'm parked... sound is always on same tempo!

What's that?? :banghead

Thanks :)
 
#4 ·
I have noticed a similar sound in mine..a few months back I had my radio off and I noticed a slight knock once every few seconds. I can't feel the knock but I can hear it. It seems to be coming from behind and below the dash. I am certain it has something to do with the climate system because occasionally when turning on the heat I get a loud knock. I wouldn't stress over it as it has zero efect on performance
 
#5 ·
Yeah... but i'm the kinda guy who wants his car to be in perfect shape (specially for rattles and strange sounds lol)...

Any more ideas of what it could possibly be??

I read in another post that blower motor is "easily" accessible from engine bay... where exactly that would be? I have to lubricate it.

Thanks
 
#9 ·
Thanks for the link, will be usefull when I have an annoying sound ;)

I read it but wasn't able to find anything that looks like the sound I get...

Well, if no one has an idea of what my problem is, I'll probably drive the car to BMW mechanic next week :banghead

Thanks :)

H.
 
#12 ·
well, when first reading this i first thought for you to check your abs brakes to see that they are working properly, i think i understand that you feel the toc noise through the brake pedal? Also you could maybe look up under the car and trace the lines and peices that connect to the pedal from the outside in the engine bay part maybe and you might find something there, i hear alot of people talking about noises in their bimmers, i too have the loud noise when heat is engauged, too bad they don't stay quiet, if you find the problem please post so i can check mine before it starts! hope this helps!
 
#16 ·
Originally posted by Henri@Mar 31 2005, 04:10 PM
That's the link for noise FAQ: http://www.bmw-forums.com/forum/index.php?showtopic=10266

:)
[snapback]322336[/snapback]​
Your Toc 3 sc, Toc noise it simple youre heater core valve. This valve sits right next to the brake master cylinder on the engine compartment. This regulates the flow of colant into the heater core, controlling its temperature.
What happens with time, the valve gets dirty inside, stuck, gets old, and so the moving part inside of it dont move smooth but rather hard, like knocking. This valve had two pistons that move up or down to open or close the coolant flow by means of a solenoid, a magnectic force moves the piston rod by current flowwing on electrical coils.
The valve gets old, and so everytime th episton moves, it doesnt do it smooth but hard, and so you feel the knock on your foot, since this is attached right next to the brake master cylinder .

Of course there is the abs system. Mounted, within the brake master cylinder, there is a brake pedal travel sensor, tell the ABS brake load, this sensor will have a moving solenoid, that you will feel moving back, disigaging, when you are atrating the car up and have you foot on the brake. Also when braking strong and wheels slip, abs pump kicks in to maintin car straight, but you know the feeling of this, you only feel it once a whille and is totally different from the continuos toc...

To make sure the toc noise is form the heater valve, put all temperature dial to cold, let the fan on, swicth the ac is you want, and give a couple a sec, eventialy the valve will stop tocing, since it closes, and so the pistong does not move anymore.

Now this valve is not a biggie, and can be replaced rather easy, but, by own experience, do not buy used valve from ebay, they normally have their rubber seals worn and the pistons dont move freely, so its worth paying the extra couple of bucks, but ulll get somethign that will last.

let us know

victor.
 
#17 ·
i have the same problem and i dont think it has anything to do with the climate system, it sounds like something may be rubbing against the driveshaft or something and thats why you can feel it under your feet, mine will do it for a little bit then stop then come back then stop, but never is it triggered by turning on the heat or a/c
 
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