1. Disconnect the wire terminal «masses» (-) from the battery.
2. Drain the coolant into a suitable container.
3. Disconnect the air intake sleeve from the air filter.
4. Remove the cylinder head cover.
5. Disconnect the fuel supply lines from the injectors and place them on a clean rag.
6. Plug the holes to the injectors and injection pump with suitable plugs (you can use rags or even paper handkerchiefs).
7. Disconnect the fuel return line from the injectors to the injection pump.
8. Disconnect the glow plug power cable.
9. Disconnect the power supply to the temperature sensors.
10. Turn out bolts of fastening of a reception pipe of mufflers from a turbocharger.
11. Disconnect the supply and return oil lines from the turbocharger, and plug the holes with clean plugs. Remove the turbocharger if necessary.
12. Remove a gear belt. Disconnect the coolant circulation hoses from the cylinder head.
14. TD engine. Disconnect the cold start accelerator cable.
15. Turn out bolts of fastening of a head of the block of cylinders in sequence of their screwing in (see illustration).
Attention! To avoid subsequent distortion of the cylinder head, it should only be removed from a cold engine.
16. Remove the cylinder head. If, due to a tight fit, the head does not detach, then tap it with a plastic hammer.
Examination
17. Remove the old seal. The sealing surfaces of the cylinder head and block must be absolutely clean, free of sealant residues.
Attention! Do not clean the sealing surfaces of the cylinder head with sharp tools. The resulting scores or scratches can cause subsequent damage to the head.
18. Check that there are no cracks on the valve seats. Small cracks no more than 0.5 mm are allowed. The cylinder head in such cases can be reinstalled for further operation.
19. Check up a head of the block of cylinders on absence of distortions. This is especially necessary if the gasket has burned through.
20. Place a long metal straightedge or straightedge along the cleaned sealing surface of the head and use a template to verify that there is no distortion greater than 0.1 mm.
AUDI advises against reworking (polishing) cylinder heads. Therefore, if the curvature exceeds 0.1 mm, then the cylinder head should be replaced with a new one.
Installation
Before installing the cylinder head, check the thickness of the new gasket. Diesel engines are equipped with cylinder head gaskets of different thicknesses. It depends on the height of the protrusion of the pistons. The volume of the combustion chamber depends on the thickness of the installed gasket. The thickness of the gasket is indicated by notches or holes of small diameter on the gasket itself (see arrow in illustration 9.0).
When replacing the cylinder head or after removing it with subsequent installation, a new gasket is installed that is absolutely identical to the previous one. This means that instead of the previous gasket, a gasket with the same number of notches or holes must be purchased and installed.
If the crankshaft parts were replaced (the crankshaft itself, connecting rods, pistons) or the old cylinder head is installed on a new cylinder block, then the piston protrusion must first be measured (see illustration 9.0a). Piston protrusion refers to the distance the pistons protrude from the surface of the cylinder block. Guided by the size of this protrusion, you should purchase and install the appropriate gasket.
Attention! The threads of the head bolts and the threads of the bolt holes in the cylinder block must be clean and undamaged. Otherwise, the tightening torque of the bolts will not correspond to the nominal. There must be no oil or liquid in the bolt holes. Failure to do so may result in rupture of the cylinder block metal.
21. Rotate the crankshaft so that none of the pistons is at TDC. Otherwise, when the cylinder head is installed, the open valve may hit the piston.
22. Lay the cylinder head gasket on the cylinder block so that its marking or inscription «OBEN» (top) facing the head of the block.
23. Reinstall the cylinder head. If there are no centering pins on the cylinder block, then in the workshops two guide pins are screwed into the holes for the bolts 8 and 10, which avoid displacement of both the head itself and the gasket at the time of installation. Instead of guide pins, two pins of the appropriate diameter can be inserted.
24. Screw in all bolts of fastening of a head of the block of cylinders and tighten them at first on the cold engine in several stages and in sequence, as shown in an illustration 9.15 with the following moments of an inhaling.
1st stage. Screw in the bolts with a torque wrench with a torque of 40 Nm.
2nd stage. Tighten the bolts with a torque wrench to 60 Nm.
3rd stage. Tighten the bolts half a turn with a wrench (180°), without interrupting the forward movement of the key.
4th stage. Warm up the engine (coolant temperature should be around 80°C) and tighten the bolts with a wrench ¼ turn (90°), without interrupting the forward movement of the key.
Attention! If the cylinder head was removed due to a damaged head gasket, the coolant must be completely drained and replaced with new. The same applies to replacing the cylinder head.
A defective cylinder head gasket can be recognized by one or more of the following:
A) loss of coolant
b) clouds of white gases from the exhaust pipe,
V) When the engine is running, air bubbles come out of the coolant expansion tank. and when the reservoir cap is opened, an active leakage of coolant occurs in the form of foam,
G) gray or brown emulsion on the engine oil dipstick due to coolant getting into the engine oil.
Attention! Coolant in the engine lubrication system can cause bearing failure. Replace the cylinder head gasket immediately. Don't start the engine! Delivery of the car to the workshop is carried out by loading onto the platform.
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