Pulse at Break Pedal

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Barbanasos

Active Member
Joined
Mar 8, 2007
Messages
470
Location
Manchester
Car
Mercedes E200 w124 and 2000 E55 AMG
Hi,

although a mercedes fan for years following my dad's trustworthy 123 I purchased an E240 1998. Everything is great with the car, but I am pretty paranoid about every vibration, little noises etc and obviously if there is sth wrong I want ot put it right. All the mechanics find the car perfect, however I do get a strange pulse through the brake pedal, almost like a heart beat.

By the way,the breaks are outstanding, the pulse is felt only as you lay your foot on the break pedal holding the car stationary.

Has anybdy experienced this, and if it is a problem what do I need to change?

Many thanks

Thanasis
 
I have exactly the same thing with my C280. I have been told it is the 'duovalve' pulsing, and that it's nothing to worry about. I find it only reallly happens when I have the interior temp setting on warm/hot. It never happens when my aircon is switched on either. To prove that its the duovalve causing this, run your car and make sure the pulse is being felt through the brake pedal, then pop your bonnet and look at, or touch the top(will be hot) of the duovalve to see if it's that, that is pulsing. It is on mine. I presume the duovalve will be the same if not similar on your car. You can see what a duovalve looks like here: http://www.mbclub.co.uk/forums/showthread.php?t=26854&highlight=duovalve
 
Thanks,

that makes sense, as the front water pipes do have a pulse themselves. If I were to replace the valve for a new one would it be the same? or the pulsing would disapear?
 
TBH, I'm not entirely sure. I have been told that the pulsing is 'normal', although my friend's car doesn't do it. Anyone else know?
 
I would have thought he pulsing would be a feature as that is how the hot water is regulated to vary the heater temperature.
Having said that I can't feel it although the valves are definately pulsing.
 
I think I will raise it with a mechanic at the dealer, and if they say that some pumps do it, I will just buy a new pump in due time, that should cure it. Thanks everyone for pointing me to the right direction.
 
I think I will raise it with a mechanic at the dealer, and if they say that some pumps do it, I will just buy a new pump in due time, that should cure it. Thanks everyone for pointing me to the right direction.

Most welcome.:D
 

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