Attention! Valve drive and oil sprayer parts have many modifications, so when replacing them, you must consult a Mercedes-Benz representative.
The valve drive is combined with the camshaft bearing caps. The rocker arms are mounted on separate short axles, which are also secured to the camshaft bearing caps. Each camshaft bearing cap has one rocker arm, controlling the intake and exhaust valves.
Hydraulic tappets are fixed in the rocker arms, and oil is supplied to them through holes in the rocker arms.
Removal
Location of camshaft bearing cap markings
Removal the engine oil spray tube
Removal the camshaft bearing cap together with the rocker arms attached to it
Removal the contact washer from the top of the valve stem
1. Remove the air filter.
2. Remove the cylinder head cover.
3. Remove the camshaft sprocket.
4. Check that the rocker arms and bearing caps are marked. The bearing caps are numbered 1 through 4 on the camshaft sprocket side, and the numbers on the bearing caps are on the exhaust manifold side (see Fig. Location of camshaft bearing cap markings). Similar markings are 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 engine oil spray tube (see Fig. Removing the Engine Oil Spray Tube).
7. Remove the camshaft bearing caps with the rocker arms attached to them. The camshaft bearing caps are installed on the guide pins.
8. Remove the contact washers from the tops of the valve stems and stack them so that they can be reinstalled later (see fig. Removing the camshaft bearing cap together with the rocker arms attached to them, Removing the contact washer from the top of the valve stem).
9. Carefully remove the camshaft from the cylinder head.
Disassembly, inspection and assembly
Camshaft
1. Check the camshaft bearing running surfaces and camshaft lobe contours for wear. If any wear is present, replace the camshaft. When replacing the camshaft, the rocker arms must also be replaced.
Valve drive
Removal the rocker arm shaft using a long M8 bolt
1. Once the camshaft bearing caps have been removed, the rocker arms can be removed from the bearing caps by removing the short rocker shafts from the caps. Before removing the rocker arms, check that they are marked and 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 inertia hammer with a special adapter. Alternatively, screw a long M8 bolt with a washer into the rocker shaft and, hitting the washer with a hammer, pull the rocker shaft out of the camshaft bearing cap (see fig. Removing the rocker arm shaft using a long M8 bolt). After removing the axle, remove the rocker arm. Store the removed parts so that they can be installed in their places later.
3. Check the condition of the contact washers for wear. If there is wear, the part in the set must be replaced.
4. Lubricate the rocker arm working surfaces with clean engine oil, then install the rocker arms on the cover and secure them with the axle. When reinstalling the parts, check that they are in place. Install the rocker arm axles so that the recess for the camshaft bearing cover mounting bolt in each axle aligns with the hole for the bolt in the bearing cover. If there are no special tools for pressing in the rocker arm axle, press in the axle using a long M8 bolt and a hammer.
Pushers
Rocker arm parts
1 – rocker arm; 2 – spacer washer; 3 – pusher; 4 – contact washer
Location of the hydraulic tappet in the rocker arm
1 – working cavity with oil; 2 – working chamber; 3 – pusher; 4 – rocker arm; 5 – spring; 6 – contact washer
Using thin steel wire to press the hydraulic tappet ball valve
1. To remove the tappet from the rocker arm, insert a suitable drift through the hole in the top of the rocker arm and press the tappet out of the rocker arm.
2. Remove the spacer washer from the pushrod socket in the rocker arm (see fig. Rocker arm parts, Location of hydraulic tappet in rocker arm).
3. Arrange the rocker arm parts in such a way that they can be installed in their proper places later.
4. Check the condition of the tappets and replace them if necessary.
5. Hydraulic valve tappets are designed in such a way that the tappet stroke to compensate for valve clearance is insignificant. This is due to the small dimensions of the hydraulic valve tappets. In order for the hydraulic tappet stroke to be sufficient to compensate for valve clearances, spacer washers of different thicknesses are used.
6. If you hear valve knocking when the engine is running, the valve clearance may not meet the technical requirements. In this case, you need to install a new spacer washer of a different thickness.
7. To determine the required thickness of the spacer washer, a special tool must be used and this work must be performed at a service station.
8. Before installing 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 tappet plunger upward, introduce oil into the working cavity of the tappet.
9. Repeat this operation until the working chamber of the hydraulic tappet is completely filled with oil (see Fig. Using thin steel wire to press the ball valve of hydraulic tappet).
10. Install the spacer washer into the tappet seat in the rocker arm with the oil passage of the washer facing the hydraulic tappet. Install the hydraulic tappet into the rocker arm.
Installation
Applying lubricant to the journals and camshaft cams
Alignment of the groove on the flange of the front part of the camshaft with the upper plane of the cylinder head
1. Lubricate the camshaft journals and cams and the bearings in the caps and cylinder head with clean engine oil and install the camshaft in the cylinder head. Turn the camshaft so that the recess in the flange at the front of the camshaft aligns with the top plane of the cylinder head (see fig. Applying grease to the journals and cams of the camshaft, Aligning the groove on the flange of the front part of the camshaft with the upper plane of the cylinder head).
2. Install contact washers on top of the valves.
3. Install the camshaft bearing caps with the cap markings facing the exhaust manifold side.
4. Install the oil sprayer, making sure that the oil supply holes in the sprayer are aligned with the corresponding holes in the camshaft bearing caps.
5. Insert the camshaft bearing cap bolts and tighten them finger tight, then tighten the cap bolts in a diagonal pattern, gradually turning each bolt one-half turn at a time until each cap contacts the cylinder head. Then tighten the bolts to the specified torque in the same pattern.
6. Check that the timing marks are aligned with the pointers, then install the camshaft sprocket.
7. Install the cylinder head cover.
8. Install the air filter.