e220 cdi brake pedal affects idle

[Charlie2007]

hello i am new to this forum, I own a 1999 e220 cdi avantgarde auto.

I have an issue regarding the idling on this vehicle.

Whenever you press the brake pedal, whether it is in Park,Reverse,Neutral or Drive the engine speed drops and hunts up and down. As soon as you lift off of the brake pedal the engine speed returns to normal.
Now the vehicle has been to an auto electrical centre and I have been told there are no faults logged within the diagnostics. Another feature is that when you disconnect the multifunction brake light switch, and bridge two of the wires together the fault is no longer present, however the ESP,BAS and ABS warning lights come on. i therefore believe the fault may be electrical. If anyone can offer me any technical advice on curing the fault I would be most grateful.

 

[television]

The brake light switch is a double circuit item and care should be take when playing around. To me it sounds like a fault in the one way valve in the servo feed pipe

 

[Charlie2007]

hi thanks for the response, can you tell me where the 'one way valve' is located for the servo feed pipe, and why you percieve that might be the problem.

 

[television]

http://www.detali.ru/cat/oem_mb2.as...647716.651&CT=F&cat=65S&SID=42&SGR=060&SGN=03

120 in the link

the valve is there to stop interaction between the engine and the brake

 

[Charlie2007]

Thankyou, I wiill check this out in the morning. Perhaps this explains the lack of a logged fault in the diagnostics.

 

[Ellsy Tanners]

http://www.detali.ru/cat/oem_mb2.as...647716.651&CT=F&cat=65S&SID=42&SGR=060&SGN=03

120 in the link

the valve is there to stop interaction between the engine and the brake

Malcolm, 120 is the retaining bolt for the fluid resovoir, i think you meant 150

hope you dont mind me saying this!

 

[panason1c]

To me it sounds like a fault in the one way valve in the servo feed pipe

If the vacuum for the brake servo was drawn directly from the inlet manifold (as is the case with most petrol engines) i would agree that the valve was probably at fault but as this is a diesel it wil have an independent camshaft driven vacuum pump? .......therefore, i'm not sure that this could cause the aforementioned erratic idling.

 

[television]

If the vacuum for the brake servo was drawn directly from the inlet manifold (as is the case with most petrol engines) i would agree that the valve was probably at fault but as this is a diesel it wil have an independent camshaft driven vacuum pump? .......therefore, i'm not sure that this could cause the aforementioned erratic idling.

This had crossed my mind, as you know diesels are not my good point, I just thought that there could be some connection.

This subject has been up before with the same symptoms maybe a search will find it

 

[Charlie2007]

Found out the injector seals have recently been replaced by previous owner at a local garage. I have inspected the injectors and it appears they are still leaking. Is it possible that when pressing the brake pedal the brake assist kicks in and slightly lowers the engine RPM, and when combined with the leaking injector seals, it causes the erratic idle?