Quick Question - W124 Headlamp Level Adjust

[Ednamillion]

I'm embarking on the long trek that is tracking down what I suspect to be a vacuum leak.

With the headlamp level adjuster not working I thought I'd tentitively start there. It appears to me that I have a vacuum in only the central line of the three running into the adjuster switch - is this 'normal'? Is it the usual 'off' or 'zero' position? Should I have a vacuum (by which I mean hear a hissing or a change in sound if I put my finger over the respective line) in all three lines simultaneously?

No doubt this will be the first of many vacuum-related queries so any advice/insight very welcome.

Edna'...

 

[wireman]

How it seems to work on mine.

under the bonnet:-
Vacuum is provided from the engines pump,(diesel, petrol its from the inlet manifold)

Via a small plastic lump which restricts the amount of air that can get through to the vacuum pump,

To the valve inside the car which adds a leak to the pipe dependent on its setting, one end = no leak, the other = all leak,

This adjusted vacuum is then applied to a belows inside each lamp unit that tilts the reflector about a pivot and against a spring.

A vacuum gauge connected to the pipe off a head light unit should show variable vacuum as the adjuster is moved.

Check all the little rubber (tube) joining pieces at the ends of each 4mm nylon tube, these tend to crack and leak as age catches up with them.

I just can't at the moment remember whether the vac tilts them up or down but Im sure it will become apparent to you.

When you are happy that its working dont forget to align the dip beam for 1.1% downwards gradient (110mm in 10metres) with the car unloaded, fully fueled and the adjuster at max height. Taking the car to QuickFit is an easy way of loosing £25 for this job.

 

[Ednamillion]

....
Via a small plastic lump which restricts the amount of air that can get through to the vacuum pump,

Wireman, thanks for the reply.

Re the above line you posted, the "small plastic lump" - are you referring to a check valve here?

BTW, I had the headlight beam adjusted without the engine running - lit the tree tops all the way home! QuickFit won't be seeing this car if I've anything to do with it...

Thanks, Edna'...

 

[wireman]

I think it is actually a restrictor to prevent excess air being drawn into the vac system, it may be a valve in addition to this but the leaky nature of the headlight vacuum control needs the air flow to be limited to work correctly. Its about 20mm dia and 30mm long, there seem to be several of differing colour on my vacuum system, so my guess is that they probably have differing inards for each vacuum circuit.

Go and get your money back from Quick Turpin, then when its a bit dark park the car on level ground head on and square to to a wall with your headlamp dip beam on.
Mark the intersection of the horizontal and sloping beam on the wall with a cross of electricians black PVC sticky tape.
Withdraw the car 10 metres from the wall and check that the horizontal is 110 mm lower than the mark and that the intersection is in the same place and has not sliped side ways.
If its more than about 5mm out find the adjusters and put the beams into the correct position, there is usualy one for up/down and another for sideways but some are a bit of both calling for a little on each adjuster to shift the beam in only one axis.
Hang a jacket over one headlamp to allow the best vision of the other ones beam pattern while you do these checks.
Dont forget to set the leveling wheel to its uppermost setting with the engine running, and take care not to put your hand or arm in the fan while you adjust the lamp units in the dark.

There is a label under the bonnet of all modern cars (another euro rule) usualy near the radiator top, bearing a headlight symbol and a figure of 1.1% or similar to indicate the designed head lamp dipped beam gradient, if yours says some thing else use that value instead of the 110mm I suggest (110mm is 1.1% of 10m).