Strange noise behind clutch pedal - gerbil wheel / flushing fluid sound

[carja01]

Ok - 2002 C4S ... and I have a weird one here.

 

Does anyone have any idea what would make a whirling, clicking sound (almost like a gerbil wheel-like sound) directly from behind the clutch pedal?   The sound definitely seems to be coming from behind (forward in the vehicle) the clutch pedal and can be stopped by pressing the clutch very slightly (movement of about a centimeter does the trick).  
 

I don’t have any of the typical issues (that I’ve read about) for a failing clutch master cylinder, but I have to admit that just moving it slightly seems to make the noise go away.  Is there any kind of valve, pump, bearing that sits just behind the wall?  
 

Here’s a link to a video I made that shows the clutch action and you can hear the noise ...

 

 

Thanks for any advice!

      -  Jason

Edited November 6, 2019 by carja01
Adding info and a video link and clarification

[carja01]

Here’s another with just the noise ... 

 

 

[judgejon]

The posting of your links needs to be cleaned up.  But, not sure how, I did see video and hear sounds.  
Bizarre.  Only thing that initially comes to mind is that sounds are somehow travelling up along clutch cable.  Not even sure that’s possible.  Is pedal secured?  Is cable from clutch ok?  I don’t think there are any pulleys in front of firewall.  Mystery. Good luck

[RFM]

In my opinion it has something to do with the thrust bearing, have this checked by a mechanic to be sure.

[Uwon]

You had a hydraulic not mechanical clutch. Does the ticking speed increase if you touch the accelerator lightly? Is it there at any time while driving?

Johan

[carja01]

3 hours ago, Uwon said:

You had a hydraulic not mechanical clutch. Does the ticking speed increase if you touch the accelerator lightly? Is it there at any time while driving?

Johan

@UwonIt does not increase when accelerating - it can be heard while driving but only when the car is in neutral (I’ll admit that the engine noise may be concealing it in gear but I’ve not heard it while in gear).

 

 It is somewhat intermittent But becoming more consistent - I purchased the car in May and the sound was present every other week, a few months later and it’s there almost daily.  
 

it’s definitely originating from just behind the clutch pedal (by behind I guess I technically mean in front as the car points). 
 

car has 68k miles, clutch done at 31k and IMS/RMS/AOS dome by previous owner at 50k

 

  JC 

 

Edited November 6, 2019 by carja01
Tagging Uwon

[carja01]

11 hours ago, judgejon said:

The posting of your links needs to be cleaned up.  But, not sure how, I did see video and hear sounds.  
Bizarre.  Only thing that initially comes to mind is that sounds are somehow travelling up along clutch cable.  Not even sure that’s possible.  Is pedal secured?  Is cable from clutch ok?  I don’t think there are any pulleys in front of firewall.  Mystery. Good luck

@judgejon - thanks, new guy - so I’ll work on my posts, sorry!  The pedal feels secure and the clutch operates completely as it should - no slippage, grinding, leaking, rough shifting, any of that ... I don’t know the status of the clutch cable, I’ll have to add that to my list of things to investigate.  Thanks! 

[JFP in PA]

2 hours ago, carja01 said:

@judgejon - thanks, new guy - so I’ll work on my posts, sorry!  The pedal feels secure and the clutch operates completely as it should - no slippage, grinding, leaking, rough shifting, any of that ... I don’t know the status of the clutch cable, I’ll have to add that to my list of things to investigate.  Thanks! 

 

There is no clutch cable in this car, it is hydraulically operated.

[carja01]

15 hours ago, RFM said:

In my opinion it has something to do with the thrust bearing, have this checked by a mechanic to be sure.

@RFM thanks - I’m reading up on the thrust bearing now, is it located in the rear of the vehicle in proximity to the engine?  The noise is emanating from forward of the clutch pedal (in the area under where the drivers side wiper blade is (roughly) but down low - basically right I’m front of the footwell.  I’m just trying to connect how the thrust bearing would make a noise in that location from so far back.  Thanks for any additional info. 

[JFP in PA]

13 minutes ago, carja01 said:

@RFM thanks - I’m reading up on the thrust bearing now, is it located in the rear of the vehicle in proximity to the engine?  The noise is emanating from forward of the clutch pedal (in the area under where the drivers side wiper blade is (roughly) but down low - basically right I’m front of the footwell.  I’m just trying to connect how the thrust bearing would make a noise in that location from so far back.  Thanks for any additional info. 

 

Fluids, like solid objects, can transmit noise.  If the throw out bearing is going south, it can transmit that noise to clutch slave, and forward to the clutch reservoir, which is just on the opposite side of the firewall from the clutch pedal.

 

Put the car on a lift and listen by the bellhousing, if the bearing is bad, you should hear it.

[carja01]

49 minutes ago, JFP in PA said:

 

Fluids, like solid objects, can transmit noise.  If the throw out bearing is going south, it can transmit that noise to clutch slave, and forward to the clutch reservoir, which is just on the opposite side of the firewall from the clutch pedal.

 

Put the car on a lift and listen by the bellhousing, if the bearing is bad, you should hear it.

@JFP in PA that definitely makes sense, I had crossed throw out bearing off the list because I’d read somewhere that it only makes noise when the clutch is depressed (my issue is when the clutch pedal isn’t depressed - and the noise actually resolves when the pedal is sent even slightly downward).   I’ll put it back in there though ... thanks! 

[judgejon]

Right on re sound travel. I was thinking shifter linkage, cables, etc, anything, something carrying sound up along center hump to front end.  E-gas too, right? So no throttle cable rattles.  Jeff is great source. 
good look with this mystery.  Post up answer for us curious types. 

[dwtaylorpdx]

ABS pump over-cycling?

[judgejon]

Good point.  But would that produce the complained of noise?   I still love Mysterious Porsche Mysteries.  

[dwtaylorpdx]

I've had one ABS pump on a BMW go south,, it made some really odd noises when the pressure pump started eating its own guts, if the accumulator does not come up to pressure,, it will run for quite a while,, You can always pull the ABS fuse and see if it still makes the noise.. Or pull the beuty cover in teh frunk and have someone turn it on whle you listen the pump is fairly obvious in my 2003..  🙂

[carja01]

10 hours ago, dwtaylorpdx said:

ABS pump over-cycling?

@dwtaylorpdx - this is a great idea because it sounds a lot like a fluid pumping noise / cycling noise ... I took the advice of pulling the ABS fuse just now though and continued to hear the noise.  It seems to becoming for just behind where the clutch master cylinder ends, possibly a bit lower than that.  Thanks for the idea, it’s one less thang I have to worry about and I’m glad it wasn’t a failing ABS pump!

[DBJoe996]

There is a vacuum line to the brake booster right behind the firewall.  Have you checked that?  Might be a bad seal or something.  See #10 here 

Brake Master Cylinder Brake Booster Pre-charge Pump

WWW.AUTOATLANTA.COM

---

 

 

[dwtaylorpdx]

The booster should have a check valve ,,, now ON my jeep when it died it made a guinea pig whistling noise..

[carja01]

9 hours ago, dwtaylorpdx said:

The booster should have a check valve ,,, now ON my jeep when it died it made a guinea pig whistling noise..

Thanks @dwtaylorpdx - I'll try to check that over lunch today.  - Jason 

[dwtaylorpdx]

The fact that the noise goes away when you move the pedal does indicate the Throwout bearing could be involved,,

YOu probably need to get it in the air and use a stethoscope on it. 

[Gummischläuche]

Hi guys ...  Just watched the Vids above .. I replaced the Clutch Slave Cyl. on mine and on my friends a while back .. AND sometimes on both 996 and 997's the PLASTIC CAP on the end of the slave cyl. cracks or breaks off , and when it breaks off its possible the "Metal on metal chirping Noise" could be the push-rod resting on the clutch fork inside the housing... pull out the slave cyl and check it out ..replace it ASAP if the plastic cap is gone !