Checking vacumn in C5 hdi

[boristhespie]

Asked re my lack of power on another forum and got this reply. Thought it detailed enoigh to post here. Whether complete i don't know but thought it may be of help to others.


boristhespie,


Message:
-----
If the car idles ok but just down on power it may be an air leak on the vacuum pipe to the turbo. Best way to check is look on the turbo for vacuum diaphragm (looks like a round space ship) one end should have a vacuum pipe coming off it and the other a linkage going to the turbo. Get someone to rev the engine and you should see the linkage move if not try the following (with the engine off). Take off the vacuum pipe connected to the vacuum diaphragm on the turbo and attach another piece of pipe to the vacuum diaphragm (must be a good fit). Suck the other end of the pipe and if the linkage moves the diaphragm is ok if not either the linkage is stuck or the diaphragm is broken. It is most likely the linkage will move and then the problem will be with the pipe between the diaphragm and vacuum pump on the side of the engine usually at the end of the head above the gearbox. This also works the servo for your breaks so if your breaks are ok then the vacuum pump, this only leaves the
pipe. The fault will be between the T off for the servo and the vacuum diaphragm on the turbo. If it is the same as the C3 you have a little bypass pipe on the T piece about 50mm long and that usually the place the pipe cracks. To check disconnect the vacuum pipe from the Turbo and start the engine. Put your thumb over the pipe and you should feel the vacuum. If you have no vacuum check and replace the pipe and hopefully all will be well.

Good luck
-----

[Paul-R]

The biggest problem on the C5 is that the damn turbo is so well hidden.

I've wanted for a long time to see if the actuator on the turbo was moving the arm properly. I'd sucked on the pipe, somewhat similarly to the way that your quote describes, and heard the diaphragm operating. The vacuum held when I closed the pipe with my tongue so the diaphragm wasn't punctured.

The closest I got to seeing the diaphragm and actuator arm was when I changed the drive shaft and was able to see it (just!) from underneath.

[wright]

i saw a lad doing a turbo on a 110 last week, he did it up on a ramp and removed the sub frame, it didn't look like a nice job