W210 Servo problem ..again !

[glenluceblue]

Same old chestnut. I've an E200 kompressor (late 2000) with a strange problem with the Servo. The brakes are excellent and normally I have no problems but here is the fault I'm experiencing;
Start car with foot lightly on brake - you can feel the Servo kick in. If I then shift into reverse gear and let my foot off the brake (foot not on accelerator) then I lose the Servo. If I then go into neutral or park and rev slightly the servo returns. If I start up and put the car in reverse, then into drive (still without touching the accelerator then I lose the Servo, but again as soon as the revs pick up the Servo comes home to mama !. If I start up and go straight to drive (without the accelerator) and inch forward then the Servo is fine. The only time this would ever be a problem is if I was boxed in between cars and needed some nimble manouvering between drive and reverse.
The last time I posted I was given some good advice regarding a test for the Non return valve between the Servo and the vacuum pump which seemed to indicate the NRV was healthy. I have spoken to mechanic offshore today who reckons when you move into reverse the engine idle speed drops and that this may lessen the vacuum created by the pump and advises, if possible, to up the idle speed a little.
Does this make sense ? Can the idle speed be altered or am I "fly by wire" ?
Has anyone had anything like this happen to them ?
I'm still offshore so cannot carry out any tests but this is doing my head in.
Help me please

 

[brandwooddixon]

This seems an odd problem and obviously I'm not the only one thinking this else there would have been a good post by now (especially from television).

I'd always thought that a loss of brake servo meant a loss of vacuum.
Perhaps your comment:

"I lose the Servo, but again as soon as the revs pick up the Servo comes home to mama !" is a clue, thus I'd agree with the mechanic that you spoke to who said that it would be an idle speed thing.

In order to look at idle speed adjustment we'd need the first 6 numbers of your VIN e.g. 210245 or 211245.

 

[television]

Is the car a petrol or diesel,,we do need the VIN next 3 210???

 

[glenluceblue]

Thanks for you interest folks but unfortunately I'm offshore at the minute with a wife who thinks VIN is for cleaning the bath ! The car is a W210 E200 Kompressor (petrol) year December 2000. If the idle speed can't be adjusted manually (or can it ?) then perhaps my NRV is just sticking slightly and therefore when in reverse (and the idle speed drops as suggested) it cannot overcome the valve intially. I would love to get to the bottom of this before going to the dealer or indie as I think the whole faultfinding process could be a costly one.
I,ll try and get the wife to supply the VIN number asap.
Thanks again
Jim

 

[glenluceblue]

The VIN number begins WDB210048
Hope this helps....me !
Cheers,
Jim

 

[BlackC55]

There was a modified servo vacuum pipe for the c-class for a similar problem but I am sure it did not apply to the 210.

Idle can not be adjusted.

It may be normal behaviour. I would love to try it and advise.

 

[glenluceblue]

Any ideas ???

 

[television]

I will look through everything when I return later in the day

 

[Ellsy Tanners]

Your car has a brake boaster pump which is normally located behind the drivers headlamp pump, follow the big black hose from the servo.

This is electric and is there to generate vacum as your engine is suppercharged i.e. air is pushed and not sucked into your engine!!

this pump my be not working correctly.

 

[glenluceblue]

Elsie, by memory the black hose from the servo runs round the bulkhead and then down into the passenger side of the engine block. I think it then T's into another hose at that point (I could be mistaken with the last bit).
Are you sure about the booster pump as I was told that my car wouldn't have the booster ?