C250 revs drop when brake pressed ??

[CHRIS STARKEY]

I have noticed that when I press the brake pedal on my C250 turbo automatic that the engine revs drop, whether it's driving or ticking over!
Does anyone with a C250 auto have the same problem?
I suspect it could be the vacuum pipes - but with so many I don't know where to start!
Any help gratefully received

cheers
Chris

 

[panason1c]

Is it a petrol model?.............if so, it could be a split diaphragm in the brake servo, a new servo would be the cure.

 

[CHRIS STARKEY]

Sorry I thought I had said - no it's a diesel engine.

cheers
Chris

 

[panason1c]

Ah, it wont be the servo then, the vacuum on a diesel is provided from an independent pump rather than from the inlet manifold as on a petrol engine.

Not really sure what else this could be, has it always done it?........could be the brake lights drawing current and loading the alternator but now i'm grasping at straws!..........try removing the bulbs and see (though i doubt thats what's causing it)

 

[CHRIS STARKEY]

No I'm fairly sure it's a leak in the vacuum pipes - I just wondered if anyone had had similar problems & knew where to look (as there's about a mile of them throughout the car!)

 

[lynall]

Chris whats it ticking over at with all accessoroies turned off? and does turning anything else elec on cause the revs to drop, air con etc?

Ps like the rangie 6x4 or 6x6?



Lynall

 

[CHRIS STARKEY]

Hi Lynall, car isn't here at the mo but it hasn't got aircon & I don't think anything else affects it - it's just like the engine dies when I touch the brakes(even when driving!) but goes back to normal when the brake pedal is released.

The Rangie is 6x4 by the way - it's been in the garage 15 years - I've just got it out to dust it off and put it on Ebay to sell it.

cheers
Chris