Intake Manifold: Testing and Inspection

WM 244601 Checking intake-air distributor on 4.8-litre DFI engines

Tools





Technical values






Checking intake-air distributor

Checking the function of the variable intake manifold =>
- The function of the variable intake manifold must be checked if there is a loss of power.
- You can check that the switching flaps, shafts and adjusting unit are functioning perfectly by activating the vacuum unit.





Activating variable intake manifold on naturally aspirated engine





1. Pull off vacuum hose on the vacuum unit. -arrow-





Vacuum connection on vacuum unit

2. Connect a commercially available hand-held vacuum pump to the vacuum unit => Connecting vacuum pump. Alternatively, the tester 9160/1 can be used.





Connecting vacuum pump

3. Use the vacuum pump to create a vacuum of approx. 600 mbar on the vacuum unit. The adjusting unit ball must move from one hole in the housing to the next -top left arrows-. The connections on the control valve must be measured independently of the vacuum check -bottom right arrows-. Vibrations make it easier to actuate the variable intake manifold while driving (adjusting elements are "shaken" free).





Visual check and control valve connections

4. Use the vacuum pump to build up a vacuum and release it again several times. Check that the adjusting unit operates smoothly and that the switching flaps can move freely in the variable intake manifold. To do this, look into the variable intake manifold using a torch and mirror when the throttle housing is removed. An endoscope can also be used if necessary. => Inner function check using a mirror





Inner function check using a mirror

5. If you suspect that the variable intake manifold is defective, check that the correct hoses are used for the control valve -1 and 2-. It is also important to check that the seals are positioned correctly with respect to the cylinder head. For details, see also -> 244619 Removing and installing intake-air distributor on DFI engines Overhaul





Control valve
Checking intake system for leaks =>
1. Fit the stoppers 9264/7 on the two air cleaner connections and push in the securing clips. => Stoppers on intake pipe





Stoppers on intake pipe

WARNING

Danger of damaging the intake system if pressure is too high.

- Intake system can burst.
- Danger of injury from flying components.

-> Do not subject intake system to excessive air pressure (max. 1.2 bar of absolute pressure).

2. Set compressed-air reducer to 0.2 bar (approx. 1.2 bar absolute pressure).
3. Push a compressed-air hose onto the connection from the stopper 9264/7 and connect the other end to the compressed-air reducer.
4. Spray the intake system systematically with a leak-locating spray. Bubbles can be seen clearly at the locations where there are leaks (e.g. -arrow- ).





View shows a leaking Y pipe

5. Seal defective areas.