Caution! After installing the hydraulic lifters, wait at least 30 minutes (it's better to postpone the launch until the morning), so that the hydraulic tappets "settle", otherwise the pistons can hit the valves.
1. Hydraulic tappets are self-regulating devices that do not require maintenance.
2. If the hydraulic lifters have become too noisy, they can be checked as follows.
3. Warm up the engine to operating temperature. Stop the engine and remove the valve cover as described in paragraph 7.
4. Turn the camshaft, grasping the central bolt of the crankshaft pulley with a socket and a ratchet, until the cams of the first cylinder are facing up - both valves are closed.
5. Using a non-metallic tool, press the tappet down, then measure the tappet stroke with a flat feeler gauge. If the tappet stroke is more than 0.2 mm before the valve starts to open, the tappet must be replaced.
6. Removal and installation of tappets is described in chapter 2B (disassembly and repair of the cylinder head).
7. If the hydraulic tappet noise occurs during short trips, replace the oil pump non-return valve installed in the rear part of the oil filter housing. To do this, you will have to remove the oil filter, dismantle the housing from the cylinder block and remove the gasket. Use a suitable wrench to unscrew the valve and tighten the new one to the prescribed torque. Install the housing together with the new filter.
Text provided by the online resource: AudiManual