brake system tapping noise felt on pedal

[iznogoud]

Another little potential problem on the 1998 323is automatic. (It is a German car after all...)

I searched the forum, including that of other sites and could not find information. I also looked in the FAQ for
possible hints and I only found the "bleed your brakes every two years" thing, which should have been done
when rotors were replaced last December (2006). So, help please!

I felt a tapping/clinging noise on the brake pedal when I drove the bimmer today. The wife says it started this
morning. The tapping or clinging noise is soft and comes from the engine bay, and it is felt on the pedal as if
the pedal responds to the noise. It is immediately followed by another such noise, and the two are 2 seconds
apart. After 5 or 6 seconds it happens again. This is when the engine is idlling; I cannot tell if it goes on while
driving. It is as if a pressure valve from the hydraulic system of the brakes is going bad, and what I am
feeling is the opening (to release the pressure that the system builds up) and then the closing. I am not
certain about this, I am just speculating. The brake fluid is full and there seem to be no leaks.

Hints and your experience is most welcome.

[PhilipWOT]

Sounds vaccuum related to me.

[iznogoud]

I kept driving the car for a day and noticed that the tapping stopped, at least for the time being.
Can I assume that it was some air bubble in the vacuum system, and that I only will need to
bleed the brake system? Puzzling, very puzzling to me this thing...

[oakley]

just check all the hoses and solid brake lines, check for corrosion and leaking etc..My solid lines went recently.. Pricey job but unfort with brakes u just cant ignore it :)

[buster318is]

just check all the hoses and solid brake lines, check for corrosion and leaking etc..My solid lines went recently.. Pricey job but unfort with brakes u just cant ignore it :)

Rule number 1 with cars;

Before you go fast, make sure you can stop just as quickly!! :thumbup:

[iznogoud]

Points well made and seriously taken. Thanks. Tapping is back on and I am going to do something about it
this week.

Ironicly, my Audi S4 B5's rear differential is whining a bit now, so I have zero cars that I can drive at the moment!
The irony is that when something appears on one, something also appears on the other car within days! Or maybe
I am just a "whiner".

[Thomas]

Interesting......this tapping noise. I am experiancing exactly the same thing. Warm idle, in drive or in park, if feel/hear the same. Please let me know what it was that you found.
Thanks!

[iznogoud]

Suntex01 and I have been trying to diagnose the problem. It is probably not from the brake system, it is
just felt on it. I started touching things near the firewall while the tapping was going on, including the BMC
(Brake Master Cylinder), the BMC booster and lines, to no avail. However, right next to the BMC, on the
passenger side, there are two lines that run into some fixture. I touched that area and felt the tapping on it.
To make sure that you are having the same problem, pop the bonnet, and put your hand right next to the
brake fluid reservoir (on the paseenger side of it) and carefully feel the lines that run to that fixture that is
barely visible below the BMC. Careful not to burn yourself for those lines are a bit hot.

Suntex01 was going to a mechanic but he has not got back to me as of today. I, on the other hand, have
been to busy crawling under my S4 to work on the bimmer... More later. Let us know what you find.

By the way, I cannot seem to find a single diagram of that part on real-oem or the bentley manual.

[BLiever23]

I got the same problem with my car a few weeks ago. heard the tapping, felt it in the brakes. the interesting thing I noticed about it is that the noise happens even when the engine is off.

I turned the key halfway so I could listen to the radio while waiting for someone, and there it was, so it seems like it's gotta be a problem with something electrical.

have you heard anything from a mechanic yet?

ps: happy new year!

[iznogoud]

I largely ignored the problem. What I noticed is that in colder weather it takes longer before the noise
starts -- it is really cold here in Minnesota nowdays.

We all seem to have ignored this particular problem, in spite of the fact that it is closely felt on the brakes
and we do not know what it really is...

[CameronSF]

This is not ABS related is it? When the ABS sensors get whacky it may think you are in a hard stop and modulate the braking force...does it do it under braking? Can you feel it through the pedal?

[iznogoud]

I cannot tell if it is ABS-related, but it does not do it when braking alone, but when the engine
is sufficiently warm. As you can read from above, others have observed the tapping when
the engine is off as well.

[suntex01]

IF your tapping is still felt after the engine is off....its most likely an electrical or HVAC problem. I read a thread that was dated a few years back....
the guy had the same problem...which he thought was related to the water valve for the HVAC that was close to the vicinity of the brake booster. You might be able to find the thread using google.
But as for my problem...I could only feel the tapping when the engine is running...that's why I always thought it was something mechanical, or at least had to deal with the braking system....
And with my problem...it sorta disappeared due to the cold weather few days back....


I got the same problem with my car a few weeks ago. heard the tapping, felt it in the brakes. the interesting thing I noticed about it is that the noise happens even when the engine is off.

I turned the key halfway so I could listen to the radio while waiting for someone, and there it was, so it seems like it's gotta be a problem with something electrical.

have you heard anything from a mechanic yet?

ps: happy new year!

[iznogoud]

I am reviving this thread. All of you who had this problem and possibly still have this problem, check your power-steering fluid.
My power-steering fluid was low so I topped it and I am pretty sure that I have not felt this tapping problem since...

Word of caution: my 1998 E36 323is with automatic transmission uses ATF (automatic transmission fluid) for the power-steering
system. Be sure to check the cap for what fluid you should be using. The power steering fluid reservoir is located on the left
side of the engine (driver's side), and you may have to pull some hoses/wires out of the way to gain access to it. It rests on top
of the power-steering fluid pump.

I would like to see some responses if possible.

[CJH]

Check your heater control valve, they can tap rather loudly, mounted to the firewall so it transmits to other parts.

http://forums.bimmerforums.com/forum/showthread.php?t=939235&highlight=heater%2Bvalve

Other valves described as buzzing or clicking in other post, click on links in several posts for other culprits & fixes:

http://forums.bimmerforums.com/forum/showthread.php?t=920030&highlight=heater%2Bvalve