Humming and droning noise at 1000 to 2000 rpm - AF49.10-P-1301AG

ENGINE 111,112, 113 in MODEL 163

ENGINE 111, 112 in MODEL 170

ENGINE 111,112, 271 in MODEL 203

ENGINE 111,112, 113 in MODEL 208

ENGINE 112, 113, 271 in MODEL 209

ENGINE 104, 111, 112, 113, 119 in MODEL 210

ENGINE 112, 113, 271 in MODEL 211

ENGINE 113, 137, 275 in MODEL 215

ENGINE 112, 113, 137, 275 in MODEL 220

ENGINE 112, 113, 275 in MODEL 230

Damage code	Cause	Remedy
	Exhaust system distorted.	Do not use a 2-pillar lifting platform. A second fitter is required to open the throttle for continued tests in the vehicle. It is absolutely essential to put the selector lever of the automatic transmission in position P and manual transmission in neutral
	This can lead to humming and droning noise at 1000 to 2000 rpm.	1 Start engine.
		2 Hang weight on rear exhaust system (picture 1). Any change in the vibration response of the exhaust system is checked. To do this, use an available weight (1.5 to 2 kg, a belt pulley for example).
		If the noise changes: ↓ 3 Slacken bolted connections. Loosen all bolted connections starting from the connecting point of the exhaust manifold.
		4 Drive for a short distance (approx. 20 m).
		5 Fasten exhaust system. Important: Fasten bolted connections free of tension starting from the exhaust manifold to the rear muffler.
		If the noise does not change, isolate the exhaust system, to do this: ↓ 6 Detach transmission bracket (picture 2). Important: Do not loosen exhaust manifold fixings.
		7 Loosen rear cross strut (picture 3).
		8 Unhook exhaust rubbers.
		9 Install exhaust rubbers (picture 4). Replace rear exhaust rubbers installed by rubber rings as per Parts ordering notes.
		Only with model 230: ↓ 10.1 Remove exhaust system stops.
		11 Warm-up the engine and allow it to run in the rpm range complained of by the customer. No cost settlement based on warranty or goodwill is possible for complaints which are attributable to customer negligence.

Picture 1: Weight on exhaust system

Fig 1: Identifying Weight On Exhaust System

Picture 2: Transmission bracket

Fig 2: Locating Transmission Bracket Nuts

Picture 3: Rear cross strut

Fig 3: Locating Rear Cross Strut

Picture 4: Exhaust rubbers installed provisionally

Fig 4: Identifying Exhaust Rubbers

PARTS ORDERING NOTES

Part no.	Designation	Quantity
A 107 492 00 82	Rubber rings	as required