as title says, when im driving my 94 c280 i can feel a strange little knock coming through all three foot pedals, it doesnt change if i push down either the throttle brake or clutch, i can feel it through the pedels the whole time when ever i push them down (throtle all the time as my foot always on it)
its like every 5 seconds a little tap it feels like.
any help form you guys heaps appreciated.
cheer :-)

 

it can be from other source and being transmitted.

only during driving?

 

um all the time when the car is running, weather drivng or stopped, its easier to tell when its stopped tho cos theres no road vibration.
it feels like sumone is just tapping the pedals like every 5 seconds, with just normal between the knocks. just a quick tap, and its the same if im reving the car or not, just consistant tap.
may pop the hood and climb around investigating

 

very interesting.

my wild guess could be the faulty clutch of the throttle valve actuator... but how it transmit the sound, eliminate this idea.

 

it doesnt transmit a sound. it is just a feeling on the pedals, u can sort of feel it knocking or tapping with your foot, not hear it

 

I bet it is your heater valves cycling, watch the smaller diameter on the right side of engine and see if it pulses at the same rate.

 

smaller diameter hose

 

Um very interesting. took it for a drive and i think it may be related to the heater as when i turned the temp up and down it sortof changed the nocking a little bit.
Any ideas on how to fix these? or do they just do this? like maby putting in on full heat for a while may clean them out/ any ideas wod be good, cheer

 

I've noticed it sometimes happens after a coolant change, seems to go away with time on most of the C class cars. Probably an air pocket at or around the duovalves or heater core.