Audi Workshop Service and Repair Manuals > A3 Mk1 > Power unit | 4-Cylinder engine (5-valve), Mechanics | Engine cylinder head, valve gear

4-Cylinder engine (5-valve), Mechanics

Servicing valve gear

Notes:

◆ Cylinder heads which have cracks between the valve seats or between valve seat inserts and the spark plug thread can be used further without reducing service life, provided the cracks do not exceed a maximum of 0.3 mm in width, or when no more than the first 4 turns of the spark plug threads are cracked.
◆ After installing the camshaft, wait for about 30 minutes before starting the engine. The hydraulic tappets must be allowed to settle, otherwise the valves will contact the pistons.
◆ After working on the valve gear, turn the engine carefully at least 2 rotations to ensure that none of the valves make contact when the starter is operated.
◆ Renew seals and gaskets.



65 Nm ◆ Use counter-hold 3036 to loosen and tighten =>Fig.13-22 Camshaft sprocket ◆ For exhaust camshaft ◆ Note installation position: narrow rim flange facing forward and TDC marking for cylinder 1 visible from the front Oil seal ◆ For exhaust camshaft ◆ Renewing Cylinder head ◆ See note => Page 15-38 ◆ Checking valve guides => Page 15-80 ◆ Reworking valve seats => Page 15-82 ◆ Dowel sleeves for bearing caps must be located in cylinder head



Valve guide ◆ Checking => Page 15-80 Valve stem seal ◆ Renewing=> Page 15-72 Valve springs ◆ Removing and installing => Page 15-72 Valve spring plate Valve cotters Hydraulic bucket tappet ◆ Checking => Page 15-69 ◆ Removing and installing => Page 15-72 ◆ Do not interchange ◆ Store with cam lobe contact surface downwards ◆ Before installing check camshaft axial clearance => Page 15-46 ◆ Oil contact surface

◆ Check radial clearance with
Plastigage (bucket tappets not installed)
Wear limit: 0.1 mm
◆ Run-out: max. 0.035 mm
◆ Checking axial clearance
=> Page 15-46
◆ Removing and installing camshafts
=> Page 15-58

◆ Must be located on dowel sleeves
◆ Dowel sleeves must be located in cylinder head
◆ Apply a small amount of sealant to sealing surface before installation
=> Page 15-66
◆ Liquid sealant

=> Parts List



Exhaust camshaft ◆ Check radial clearance with Plastigage (bucket tappets not installed) Wear limit: 0.1 mm ◆ Run-out: max. 0.035 mm ◆ Checking axial clearance => Page 15-46 ◆ Removing and installing camshafts => Page 15-58 Bearing cap for exhaust camshaft ◆ Must be located on dowel sleeves ◆ Dowel sleeves must be located in cylinder head ◆ Note installation position ◆ Installation sequence => Page15-62 10 Nm 10 Nm Drive chain ◆ Check for wear ◆ Mark position of chain before removing=> Page 15-61 ◆ Removing and installing: => "Removing and installing camshaft," Page 15-58

=> Parts List



Inlet valve ◆ Do not rework, only grinding-in is permitted ◆ Valve dimensions => Fig. 15-45 ◆ Checking valve guides => Page 15-80 ◆ Reworking valve seats => Page 15-82 Oil seal ◆ For inlet camshaft ◆ Renewing=> Page 15-53 Hall sender rotor ◆ Note installation position: locate lug in notch on camshaft Washer ◆ Conical ◆ Note installation position 25 Nm Housing for Hall sender -G40 10 Nm

→ Fig. 1 Valve dimensions

Note:

Inlet and exhaust valves must not be reworked. Only grinding-in is permitted.

Caution

◆ Worn exhaust valves with sodium filling must not be disposed of until they have been treated as follows:
◆ The valves must be sawn into two sections with a metal saw at a point between the centre of the shaft and the valve head. They must not come into contact with water when this is done. Then throw the valves into a bucket of water (not more than ten at time). Then step back because a chemical reaction occurs when the sodium filling burns.
◆ After this treatment the valves can be disposed of in the normal way.

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