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View Full Version : Servo vacuum pipe weakness - resolved


MercedesGenIn
06-14-2015, 08:43 PM
The half inch rigid black plastic vacuum pipe that runs from the front mounted vacuum pump to the brake servo has given problems on our UK 4cyl Sprinter fleet.

I am mentioning this so others with Sprinters of the same engine configuration can be aware of this issue and perhaps check out their own vac pipe for the start of the same issues.

What happens is the underside of the pipe rubs both on the radiator trim and on occasions on the innermost lip of the slam panel. The Sound insulation from inside the bonnet sometimes sags a little and adds pressure to the pipe. What happens over a period is the underside of the pipe wears against these surfaces and thins, eventually cutting through to a pin-hole, that deteriorates the vacuum supply to the vehicle.

This in turn makes the brake pedal hard to react, reducing efficiency and has caused some turbo actuator issues.

One van was noticed to have a harder than normal brake pedal, this was the discovered fault. On checking all the other similar vans in the fleet (x4) each one showed the same wear to the two areas under the vacuum pipe. Its impossible to see unless you remove the pipe from the vac pump spigot, turn it over and look underneath.

After all the wearing pipes were replaced the first idea was to cut some rubber hose and jacket the pipes in the offending areas, then the perfect solution was discovered. At the 12 o'clock position of the fan cowling, identify the front moulding radius of the upper section and drill two 1/4" holes in the plastic, one half inch behind the other and secure the vac pipe with a simple tie wrap.

http://sprinter-source.com/forum/picture.php?albumid=246&pictureid=1798

This prevents any rubbing of the pipe on associated metalwork and of course stops it vibrating against anything that lies in its path. What looks good with the hood/bonnet up is not always the case once it is down. Just take a look at the fuel filter supply hose connection and see how that will have probably worn a spot on the the insulation on the hood!

Hope this is of use to someone, it maybe there is some clip that is missing/lost, in all cases on my fleet, but this is at least a good preventative workaround and at the very least worth a look at just to make sure all is well on your vehicle.

All the best Steve