In the 6-cylinder engine, the timing belt guard is also secured with mounting brackets (arrows). To remove the right half of the protective cover, you must additionally remove the tension roller of the V-ribbed belt (large hex socket bolt).
Removal of a casing of a gear belt
4-cylinder engine: Press out the two retaining clips at the top of the casing.
Remove the upper part of the casing.
When installing, make sure that the bottom edge of the skin / ha is correctly inserted into the upper part, otherwise the casing will not hold.
It is usually enough to remove the upper part of the casing. If you need to remove the lower part too:
Shine V-Belt (see chapter «Generator»)
Unscrew the V-belt pulleys on the crankshaft and water pump.
Loosen and remove the lock bolts and nuts on the bottom of the toothed belt guard.
When installing the V-belt pulley bolts, tighten to 20 Nm, nuts and bolts of the toothed belt guard to 10 Nm.
5-cylinder engine: Press out the two retaining clips at the top of the casing.
Remove the top part of the toothed belt guard.
Unscrew and remove the fixing bolts of the lower part of the casing.
When installing, tighten all bolts to 10 Nm.
6-cylinder engine: Remove poly V-belt and tensioner pulley for poly V-belt (chapter «Generator»).
On each half of the casing of the toothed belt, remove one tension clamp at the top and bottom
Carefully remove the cover from the rest of the fasteners.
Checking the condition of the toothed belt
Remove toothed belt guard.
The toothed belt must be free of cracks and traces of grease.
The flanks of the teeth must be solid and without signs of wear.
In order to visually check the belt along its entire length for integrity, you should rotate the engine, as described earlier.
A damaged toothed belt must be replaced!
Checking the toothed belt tension
Belt tension is checked on Audi models at the following locations.
On a 4-cylinder engine, the toothed belt guard is removed after loosening both mounting brackets (arrows).
Removing the toothed belt guard of the 5-cylinder engine after loosening both mounting brackets (arrows).
Toothed belt (2) A 4-cylinder engine is properly tensioned if it can be twisted 90 degrees between the camshaft timing belt gears (1) and intermediate shaft (the intermediate shaft is not visible in the figure).
4-cylinder engine: between the camshaft and countershaft gears.
5-cylinder engine: between the gears of the camshaft and the coolant pump.
6-cylinder engine: between the camshaft gear and the upper guide roller.
A cold toothed belt can be folded under normal tension (twist) at 90° (right angle) only thumb and forefinger.
Note: A whistling sound after starting a cold engine, which increases with higher engine speeds, indicates that the toothed belt is too tight.
Tensioning the toothed belt
The toothed belt tension can only be adjusted when the engine is cold.
First, be sure to remove the toothed belt guard.
When working with a 4-cylinder engine, a special wrench is used in the workshop, for example Matra V 159.
Loosen the clamping bolt on the toothed belt tensioner.
Turning the tension roller counterclockwise with a wrench tensions the toothed belt.
Tighten clamping bolt to 20 Nm.
Without a wrench, you need to proceed as follows: insert a strong screwdriver into one of the holes in the camshaft toothed pulley, turn it slightly to the left so that the toothed belt loosens.
Now you need to loosen the clamping bolt and place a small screwdriver at an angle to the place shown in the bottom picture on the next page. Thus, it is possible to rotate the eccentric of the tension roller until the desired tension of the toothed belt is established. Naturally, during this procedure, you need to firmly hold the camshaft. Then tighten the clamping bolt and recheck the toothed belt tension.
When working with a 5-cylinder engine, slightly loosen the fixing bolts of the tensioner.
To tension the toothed belt, turn the tensioner with a hexagon wrench to a torque of 25 Nm (torque wrench) clockwise.
Hold tensioner in this position and tighten bolts again to 10 Nm.
Checking the toothed belt tension on a 5-cylinder engine (left illustration) and 6-cylinder engine (right illustration) proceeds in the same way that has already been described in the caption to the illustration showing a 4-cylinder engine. Timing belts must be tensioned so that they can be rotated through 90°. The illustrations show the places where the belt tension must be checked.
Shown here is a temperature sensitive idler pulley for a 5-cylinder engine. The numbers indicate:
1 and 3 - fixing bolts;
2 - hexagon, into which the key is inserted when the toothed belt is tensioned;
4 - thermoelement;
5 - mounting bolt for tension roller (6).
6-cylinder engine: Remove poly V-belt and poly V-belt tensioner.
Loosen clamping bolt (socket wrench 8 mm) on the tension roller.
Using an 8 mm Allen key, turn the tensioner pulley to the right until the correct toothed belt tension is established.
Hold the tension roller in this position
Using a second Allen key 8 mm, tighten the clamping bolt of the tension roller (45 Nm).
All types of engines: rotate the crankshaft one revolution and check the tension of the toothed belt again (see previous section).
Toothed belt replacement, variable valve timing
A description of the operations for replacing the toothed belt is necessary not only for the actual replacement work, but also when removing and installing the cylinder head, for which it is imperative to remove the toothed belt.
Installing a toothed belt logically includes variable valve timing. But so that there are no misconceptions: the valve timing does not change during the wear process. They can only be adjusted once if the toothed belt has been removed before.
Note: The valve timing mechanism and the crank mechanism work in harmony (see beginning of chapter) only with correctly set valve timing. Incorrect valve timing results in low engine power and can, in extreme cases, cause even severe engine damage when the piston head hits the valves that were not closed in time. Different types of engines have different regulation.
Can you do it yourself?
A complete replacement of the toothed belt on 5- and 6-cylinder engines is only possible with the use of special tools. Therefore, unfortunately, this work is not for home conditions.
When working with a 5-cylinder engine, to remove the toothed belt, it is necessary to remove the damper in front of the crankshaft, and finally put it back in place, which is only possible with a special extension (2079) for torque wrench and counter stop (2084).
On the left is the tensioner roller of the toothed belt of a 4-cylinder engine. Designations:
1 - clamping bolt;
2 - here you can install a tool for tensioning the toothed belt. The arrow shows the direction of rotation to tension the belt.
Right: tension roller (arrow) The 6-cylinder engine is hidden on the right front on the cylinder block.
Left: when working with a 4-cylinder engine when installing a toothed belt, the marking on the countershaft gear and the mark on the V-belt pulley (in the illustration are marked with arrows) must be in the same plane (in a row).
Right: the markings on the camshaft belt sprocket must match at the same time (2) with arrow mark (1) back of the toothed belt guard.
When replacing only the cylinder head, the belt remains intact at the bottom of the crankshaft gear, so no special tools are required.
When working with a 6-cylinder engine for variable valve timing (what is needed after replacing the toothed belt and removing the cylinder heads) camshafts and crankshaft must be fixed with special tools (tools 3242 and 3243) exactly at TDC.
Working with a 4-cylinder engine is no problem. No special tools are needed to replace the toothed belt.
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