2.1.9. Removal, survey and installation of a distributive belt and asterisks of its natyazhitel

This procedure belongs only to M20 and M40 engines.

Before removal of an asterisk of a cam-shaft from the M40 engine it is necessary to buy the tool for deduction of a cam-shaft at the procedure of installation (see item 12).

If the radio receiver of your car is equipped with system of protection against theft, make sure that you gathered the correct code before a battery detachment.

If after connection of the battery of an inscription on an instrument guard appeared not in that language, address the Section System of Protection of the Audio System from theft and language of an instrument guard where the procedure of installation of the necessary language is described.



  1. Disconnect a negative wire of the battery.
  2. Uncover a distributive belt (see the Section Removal and installation of covers of a distributive belt).
  3. On M40 engines drain the cooling system (see the Head Routine maintenance of the car), then disconnect a hose, you otboltit a casing of the thermostat and remove the thermostat (see the Head the Cooling system).
  4. Bring the piston No. 1 into the provision of VMT (see the Section Reduction of the Piston of the First Cylinder in the provision of the top dead point (TDP)).

After installation of the engine in the provision of VMT do not turn distributive or cranked shaft until the distributive chain is established. If to turn a cam-shaft or the crankshaft at the removed distributive chain, valves can strike pistons, having caused serious internal damages of the engine.

  1. On M20 engines the tag on cranked to a shaft has to be combined with a tag on an internal cover.
  2. The tag on an asterisk of a cam-shaft has to be combined with the convex line on a head of cylinders.
  1. On M40 engines apply a combination tag on an asterisk of a cam-shaft and on a back distributive cover for the subsequent correct assembly.
  1. On M20 engines slightly release two fixing bolts of a roller of a natyazhitel and take away a natyazhitel towards the water pump. Having weakened a tension of a distributive belt, tighten a fixing bolt.
  1. On M40 engines release a fixing nut of a natyazhitel and by means of a six-sided key turn a natyazhitel clockwise. It will weaken a tension of a distributive belt. Tighten a fixing nut to enshrine a natyazhitel in this provision.
  1. If you are going to establish the same belt, mark it with the arrow specifying the direction of rotation.

It is not recommended to use the taken-off belt if it not absolutely new. For M40 BMW engines every time when weakening a roller of a natyazhitel recommends to replace a distributive belt.

  1. Take off a distributive belt from a roller (rollers) and from other asterisks. At removal of a distributive belt from engines on the models having a crankshaft nave, two-piece happens very difficult to remove it from a nave, but it is much easier, than to remove all assembly of a nave of the crankshaft which fastens very hard bolt
  1. If there is a need to remove the crankshaft or an asterisk of an intermediate shaft, give an asterisk bolt, holding at the same time an asterisk in an immovability. For deduction of an asterisk wrap up it a piece of an old distributive belt (so that the party with teeths was hooked for asterisk teeths) or a piece of skin, then hold it by means of a special wrench. If there is no such key, densely squeeze the ends of a piece of a belt or skin a clip. Before weakening a bolt, make sure that you have a necessary tool for installation of a cam-shaft described in the following paragraph. Removal of a distributive belt from a crankshaft asterisk for the M40 engine is represented on a photo. Removal of an asterisk of a cam-shaft for the M40 engine is represented on a photo.

Do not use a belt which you are going to establish, for keeping of an asterisk. Besides, the asterisk of a cam-shaft should be held very reliably since if it turns more, than by several degrees, valves can strike pistons.

On M40 engines the asterisk is not established on distributive to a shaft at once by means of a key as the flute on the end of a cam-shaft allows an asterisk to turn by several degrees in both directions. The fixing bolt fixes an asterisk on a cone after installation of a cam-shaft by means of the special tool.

  1. The special BMW tool for installation of a cam-shaft on M40 engines represents a metal plate which is put on a square ledge near cylinder No. 1 cams on a cam-shaft - at first it is necessary to uncover a head of cylinders.
  1. If you did not manage to buy such tool, it can be made in house conditions of a metal plate. The task consists in that this tool held a square ledge on a cam-shaft under the necessary corners in relation to the top plane of a head of cylinders (i.e. to adjoin to a surface of a cover of a head of cylinders).
  1. If there was a need to remove an asterisk of a bent shaft, give the central bolt of a nave of the crankshaft, holding at the same time the crankshaft in an immovability.

Return of a fixing bolt of a nave of the crankshaft demands use of the heavy-duty holding adaptation since this bolt is tightened with very big effort. BMW for this purpose has a special tool No. 112150 (for M20 engines) or 112170 (for M40 engines). If you do not manage to get or borrow such tool, look in local shop of auto parts or in auto repair shop for something suitable for this work. Pay attention that the tool No. 112170 fastens bolts to the back party of a head of cylinders and is brought into gearing with a gear wreath of a flywheel therefore this tool can be used only at the removed transmission or at the engine removed from the car.

On a photo the tool manufactured in house conditions for keeping of the crankshaft in an immovability is represented during weakening of a bolt of a pulley of the crankshaft (the engine is removed for the best review).

On models with a nave, two-piece, after removal of an external part of a nave you will need to remove an asterisk by means of a stripper with a clip (which is available on sale in any shop of auto parts). During the work with a stripper screw the central bolt of the crankshaft approximately on three turns and use it as the bearing point for the central bolt of a stripper.




  1. Check a distributive belt for existence of cracks, signs of wear and damages. At detection of any of the listed defects replace it.
  2. Also examine asterisks on existence of any signs of uneven wear or the damages demanding replacement of an asterisk.

When replacing any parts consult at the specialist of your dealer office not to doubt that you use compatible parts. On M20 engines asterisks are released recently, tension rollers and distributive belts are marked by "Z 127". Replacement of a distributive belt on M20 engines means that it has to be established as well a natyazhitel of a latest model if it was not made earlier.


  1. Examine a tension roller and, on M20 engines, a spring of a natyazhitel. Twist a roller of a natyazhitel to make sure that it rotates freely, without noise or a side play.

At installation of a new distributive belt the new natyazhitel is also recommended to establish.



  1. On the M20 engine establish a spring / натяжитель so that it was possible to establish a distributive belt without tension.
  2. Establish asterisks, working as it should be, the return to removal; tighten fixing bolts with the required effort. On M40 engines turn a cam-shaft asterisk clockwise as far as the adjusting flute allows, then tighten a fixing bolt with initial effort from 1 to 3 Nanometer.
  3. If you establish an old belt, make sure that the arrow put earlier for the indication of the right direction of rotation is sent to the necessary party (the belt has to rotate clockwise if to look at the engine).
  4. Establish a distributive belt, having placed it at first under a crankshaft asterisk that it rounded a casing. Lead round a belt around other asterisks.
  5. At last, put on a belt rollers of a natyazhitel.
  6. On M20 engines weaken bolts of a natyazhitel that the spring pulled a belt.


  1. On M20 engines slightly press on a natyazhitel behind to make sure that the spring pulls a belt. Do not tighten bolts while you press on a natyazhitel; slightly tighten them only after release it.
  1. On M40 engines to an otboltita also uncover a head of cylinders, then by means of the special tool enshrine a cam-shaft in the provision of VMT (see item 13).
  2. On M40 engines weaken a fixing nut of a tension roller and the help of a six-sided key turn a roller counterclockwise until the belt does not stretch. The turning method on 90o for check of a tension of a distributive belt is not rather exact for this engine therefore it is strongly recommended to get the special BMW tool for check of a tension of belts (apply 32±2 divisions on the tool).
  1. With a sufficient accuracy it is possible to use also a key hexagon and spring scales.
  1. Make sure that spring scales are established, as shown in a photo as the roller of a natyazhitel is established on the clown, and otherwise indications will differ from real. Spring scales have to be fixed on a key hexagon at distance of 85 mm from the center of a tension roller, and the enclosed force has to be equal to 2.0 kg.
Size A = 85 mm.
  1. Tighten a fixing nut with the required effort to enshrine a natyazhitel in the necessary provision.

It is very important that the distributive belt was tense correctly. If to draw it, it will hoot, and besides, it can be easily damaged. If to pull it it is too weak, it can "jump up" on asterisks.

  1. Check correctness of combination of distributive tags on distributive and cranked shaft.
  2. Turn a bent shaft clockwise on two whole revolutions. (At first remove the adjusting tool from a M40 engine cam-shaft).

The new belt needs to be stretched. If not to make it, the natyazhitel of a belt will be too freely fixed that can lead to damages.

  1. On the M20 engine weaken bolts of a roller of a natyazhitel, then tighten them with the required effort.
  1. On the M40 engine weaken a fixing nut of a roller of a natyazhitel and adjust a tension of a distributive belt as it is described in item 8. In conclusion tighten a nut of fastening of a roller of a natyazhitel, then completely tighten a cam-shaft asterisk bolt if it was earlier weakened.
  1. Double-check combination of distributive tags. If they are not completely combined, remove and establish a distributive belt.
  2. You make the rest of installation as it should be, the return to removal.