Attention! Parts of the valve drive and oil sprayer have many modifications, therefore, when replacing them, it is necessary to consult a Mercedes-Benz representative.
Arrangement of bolts of fastening of a forward cover of the bearing of a camshaft
The valve drive is combined with the camshaft bearing caps. The rocker arms are mounted on separate short axles, which are also fixed to the camshaft bearing caps. Each camshaft bearing cap has one rocker arm that controls the intake and exhaust valves.
Hydraulic pushers are fixed in the rocker arms, the oil supply to which is carried out through the holes in the rocker arms.
Removing
1. Remove the air filter.
2. Remove the camshaft sprocket.
3. Unscrew the bolts and remove the oil sprayer from the top of the camshaft bearing caps.
4. Check that the rocker arms and bearing caps are marked. The bearing caps are numbered 1 to 6 on the camshaft sprocket side, and the numbers on the bearing caps are located on the exhaust manifold side. A similar marking is also applied to the cylinder head under the camshaft.
5. Loosen the camshaft bearing cap bolts evenly and gradually in a diagonal sequence. Once the valve spring pressure has ceased, unscrew the bolts completely. When unscrewing the bolts, mark the location of the engine oil spray tube brackets.
6. Remove the camshaft bearing caps together with the rocker arms attached to them. The camshaft bearing caps are mounted on guide pins.
7. Remove the camshaft. If equipped, remove the camshaft end play adjustment washer located near the front bearing.
Disassembly, inspection and assembly
Camshaft
1. Check the running surfaces of the camshaft bearings and the contours of the camshaft lobes for wear. If there is any wear, replace the camshaft. When replacing the camshaft, the rocker arms must also be replaced.
Valve drive
Using the M8 bolt (1) for extracting the rocker shaft
When installing the axle, the notch on the side of the axle (arrow) must align with the bolt (3) camshaft bearing cap fasteners
1. After removing the camshaft bearing caps from the bearing caps, the rocker arms can be removed by removing the short shafts of the rocker arms from the caps. Before removing the rocker arms, check that they are marked, and also note the location of the rocker arms relative to the camshaft bearing cap.
2. To remove the rocker shaft from the camshaft bearing cap, use an inertial hammer with a special adapter. Alternatively, screw a long M8 bolt with a washer into the rocker shaft and, by hitting the washer with a hammer, pull the rocker shaft out of the camshaft bearing cap (see fig. Using an M8 bolt to remove the rocker shaft). After removing the axle, remove the rocker arm. Store the removed parts in such a way that they can be reinstalled later.
3. Check the condition of the contact washers for wear. In the presence of wear, it is necessary to replace the part as a set.
4. Lubricate the working surfaces of the rocker arms with clean engine oil, then install the rocker arms on the cover and secure with the axle. When reinstalling the parts, check that they are in place. Install the rocker shafts so that the notch for the camshaft bearing cap bolt in each axle aligns with the bolt hole in the bearing cap. In the absence of special tools for pressing the rocker shaft, press the shaft using a long M8 bolt and a hammer.
Hydraulic pushers
Rocker parts
1 - rocker; 2 - gasket washer; 3 – hydraulic pusher; 4 - contact washer
Check of serviceability of a hydraulic pusher of valves
1 - steel wire with a diameter of 1.5 mm; 2 – oil supply chamber; 3 - ball valve
1. To remove the pusher from the rocker arm, insert a suitable drift through the hole in the upper part of the rocker arm and press the pusher out of the rocker arm.
2. Remove the spacer from the pushrod seat in the rocker arm (see fig. rocker parts).
3. Arrange the parts of the rocker in such a way that they can later be installed in their places.
4. Check up a condition of pushers and, if necessary, replace them.
5. The health of the hydraulic tappets can be checked as follows (see fig. Check of serviceability of a hydraulic pusher of valves):
- a - install the hydraulic valve tappet vertically;
- b - fill in the oil supply chamber at the top of the tappet with clean engine oil;
- c - Using a 1.5 mm diameter steel wire inserted through the hole in the center of the plunger, press the ball valve and release it. Press the ball valve until the working chamber of the hydraulic pusher is filled with oil;
- d - Using a wooden hammer handle, press firmly on the top of the pusher piston for 10 seconds. In this case, the pusher piston must remain in place;
- e - if the plunger piston moves down, the plunger must be replaced.
6. Hydraulic valve lifters are designed in such a way that the amount of travel of the pusher to compensate for valve clearance is negligible. This is due to the small size of the hydraulic valve lifters. In order to ensure that the stroke of the hydraulic tappet is sufficient to compensate for valve clearances, shim washers of various thicknesses are used.
7. If valve clatter is heard while the engine is running, the valve clearance may not be up to specification. In this case, a new washer of a different thickness must be installed.
8. Determining the required shim thickness requires the use of a special tool and this work must be done at a service station.
9. Before installing the hydraulic tappets, they must be filled with engine oil. To do this, install the tappets vertically in a container filled with clean engine oil. Press the ball valve with a thin steel wire and, moving the pusher plunger up, introduce oil into the working cavity of the pusher. Repeat this operation until the working chamber of the hydraulic pusher is completely filled with oil.
10. Install the washer into the pusher seat in the rocker arm with the washer oil passage towards the hydraulic tappet. Install the hydraulic pusher in the rocker.
Installation
1. Check that the camshaft end play adjustment washer is installed near the front bearing.
2. Lubricate the camshaft journals and cams and bearings in the covers and cylinder head with clean engine oil and install the camshaft in the cylinder head. Rotate the camshaft so that the notch on the flange at the front of the camshaft is aligned with the top plane of the cylinder head.
3. Install the contact washers on top of the valves.
4. Establish covers of bearings of a camshaft, and marking of covers has to be from a final collector.
5. Install the oil sprayer, ensuring that the holes for the oil supply to the sprayer are aligned with the corresponding holes in the camshaft bearing caps.
6. Insert the camshaft bearing cap bolts and finger-tight, then tighten the cap bolts in a diagonal sequence gradually turning each bolt half a turn in one pass until each cap contacts the cylinder head. Then, in the same sequence, tighten the bolts to the required torque.
7. Check that the timing marks are aligned with the pointers, then install the camshaft sprocket.
8. Install the cylinder head cover.
9. Install the air filter.