It should not change that much. If the pressures are OK and the auxillary fan is working, you shouldn't have to change the idle. If the belt is new and properly tight, you will not get any squeal..IF you did, it would squeal every time you shut down the engine.

To raise the idle, there is a 14mm nut below an adjustment screw on the side of the injection pump. IF you loosen the nut and turn the screw clockwise, it will raise the idle.

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Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS