The wear process is usually divided into three periods: running-in; normal wear; emergency.
In the process of running-in, intensive wear of rubbing parts occurs, as a result of micro-roughness of the mating surfaces, they decrease, the contact area increases, the specific loads decrease, the wear rate slows down and turns into normal wear.
The period of normal wear is characterized by a relatively small growth rate of the gap in the interface, however, when a certain gap is reached, the wear rate increases sharply, which indicates the beginning of emergency wear. Operation of the unit with emergency wear leads to breakdowns that cannot be restored.
During operation, it is very important to subject the assembly to repair before emergency wear occurs. at the same time, repair costs will be significantly lower than when repairing a unit with emergency wear. Before making a decision on repair, it is necessary to diagnose the state of pairing in the units. As a rule, diagnostics is carried out by indirect signs, such as increased noise, vibration, oil consumption, crankcase gas breakthrough, power loss, etc. For better diagnostics, the unit must be disassembled, the parts washed, inspected and subjected to micrometering.
Based on the results of inspection and measurements, a decision is made to continue operation without repair or a repair is determined. In this case, one should be guided by the following considerations: if the actual dimensions of the parts are within the tolerance fields permitted by this Manual, then the continued operation of the unit without repair is possible; if the dimensions are out of tolerance, then repair is necessary.
The expansion of the tolerance fields given in this Guide should be regarded as the possibility of using the residual resource of the node without restoring the pairing. In the case of repair of the unit during the restoration of interfaces, the extension of the tolerance fields beyond the established ones is not allowed.
The repair technology is usually divided into four stages of work: disassembly - washing; control - sorting; repair itself: restoration of the micro and macro geometry of the surfaces of parts and its physical and mechanical properties; assembly with preliminary control of parts entering the work.
Dismantling and washing operations are carried out in several stages: external washing of the unit, partial disassembly, nodal washing, disassembly into parts, washing and cleaning of parts. Before checking-sorting, thoroughly clean all parts from dirt and carbon deposits, degrease, rinse and dry (compressed dry air). Clean oil channels and holes in parts, flush under pressure and blow with compressed air.
Parts made of aluminum and zinc alloys are not allowed to be washed in alkaline solutions used for washing steel and cast iron parts, since aluminum and zinc dissolve in alkalis.
In the process of checking parts, breaks, cracks, dents, shells and other damages should be detected by external inspection. In critical parts, check for cracks using a flaw detector. The dimensions of parts must be controlled in places of greatest wear. Gear teeth wear out unevenly, so when checking them, at least three teeth located at an angle of 120°should be measured.
In view of the need to guarantee the operation of gears during the entire overhaul run, chips on the teeth and chipping of the working surface of the teeth of a fatigue nature are not allowed.
Assembly units such as: connecting rod with connecting rod cap, cylinder block with main bearing caps, gearbox and final drive gears must not be dismantled. It is possible to dismantle the remaining assembly units, but if a decision is made to continue the operation of the mating elements without repair, then it is not advisable to dismantle them.
In all cases of repair by welding and surfacing, the weld should not have slag inclusions, unchecked areas, undercuts and other defects. Clean the seam after welding. Eliminate metal sags so that they do not interfere with the installation of mating parts.
Holes with worn or damaged threads are repaired by cutting threads of an increased repair size, or by welding holes, followed by threading of a nominal size. Setting of screws and spiral threaded inserts.
The use of threaded inserts is preferable for reasons of restoration quality and labor costs. Parts submitted for assembly must be clean and dry. Threaded connections should not have comments. Disposable self-locking threaded fasteners must be replaced with new ones. If it is impossible to use new self-locking parts, when installing the old ones, it is necessary to stop them from turning away.
When assembling, install new gaskets and seals. During assembly, lubricate the rubbing surfaces of the parts with clean oil. When installing rubber seals, lubricate the working surface of the cuff to avoid damage during installation. When installing oil seals with a metal case, lubricate the gland socket with a thin layer of sealant.
Assemble units and assemblies in accordance with this Manual. Using a measuring tool, check the dimensions of the parts forming the fit before assembling.
When assembling parts that have a movable fit in mating, their free relative movement must be ensured, without jamming. Install bushings, rings of ball and roller bearings using mandrels. When pressing bearings, force must not be transmitted through balls or rollers. Pressing tools must rest against the pressed ring. The pressing force must be aligned with the bearing axis to avoid misalignment of the rings.
If, according to the assembly conditions, the installation of critical parts is carried out by hitting a hammer, it is necessary to use mandrels and hammers made of non-ferrous metals, plastics, rubber, as well as fixtures and gaskets for pressing parts.
The keys must be firmly seated in the keyways of the shafts using a hammer or a non-ferrous mandrel. Play of the keys in the grooves of the shafts is not allowed.
Studs must be screwed into dry and clean threaded holes tightly without play. Details should be put on the studs freely. Bending of the spires when installing parts on them is not allowed, fastening the assembly or part with several nuts or bolts should be done evenly around the perimeter - first preliminary, and then finally.
All nuts or bolts of the same joint must be tightened to the same torque, unless otherwise specified in Appendix. The tightening torques of the fastening elements are given in the Appendix to this Manual, while it is necessary to use wrenches that allow limiting the torque.
The list below includes a minimum of standard tools necessary to perform operations for the removal, disassembly, repair, assembly and installation of vehicle components and assemblies:
- combination wrench set (1/4» — 1», 6 - 19 mm);
- set of interchangeable socket heads (1/4» — 1», 6 - 19 mm);
- ratchet reversible drive with crank (250 mm);
- universal cardan type joint for socket heads;
- torque wrench;
- metalwork hammer (250-300);
- mallet (wood, rubber or plastic);
- set of wrenches;
- set of external socket wrenches;
- candle key;
- a device for adjusting the candle gap;
- a set of measuring probes;
- iipelny key for pumping brakes;
- screwdrivers («-» 8x150 mm. 8.5x150mm; «+» 2x6x150 mm, 3x8x203 mm);
- combined pliers;
- clamping pliers;
- dielectric pliers;
- pliers-platypuses;
- chisel (13 mm);
- hacksaw for metal with a set of blades;
- a set of files;
- tire pressure gauge; grease gun;
- non-ferrous metal scraper;
- wrench for removing the oil filter;
- locksmith's scriber;
- punch;
- beards (1.8; 3.3; 4.8mm);
- steel ruler-bar;
- a set of props;
- jack,
- electric drill 3/8» (9 mm) and a set of drills;
- fine sandpaper;
- wire brush (big and small);
- oil container;
- container for antifreeze;
- filling funnel.
For high-quality repair operations, it is also necessary to have special tools and devices:
- for compressing valve springs;
- for cleaning the grooves of piston rings;
- for compression of piston rings;
- for removal/installation of piston rings;
- for centering the clutch disc;
- to remove the steering wheel damper;
- for removing the caps of the springs of the brake pads;
- compressometer;
- countersink and hone for processing the edge and mirror of the cylinder;
- hone for processing the mirror of the brake cylinder;
- cylinder diameter gauge (caliper);
- a set of micrometers and a caliper;
- device for removing hydraulic pushers;
- universal puller;
- ball joint puller;
- impact screwdriver;
- stroboscope with adapter;
- manual combination pump (vacuum/pressure);
- tachometer;
- tester;
- a set of taps and lerok;
- lifting rigging;
- tools for dismantling brake springs;
- floor garage jack. A complete list of special devices and their purpose is given in the Appendix to this Manual.
Fasteners
Fasteners include a set consisting of nuts, bolts, studs, rivets, washers and locking elements, designed to connect two or more parts. Connections are detachable, the main type is threaded and one-piece - riveted and welded. All threaded fasteners to be installed must be clean, straight, with intact threads and strict edges of the heads of the bolts and nuts on which the wrench heads are installed.
Special self-locking nuts with nylon and fiber inserts cannot be reused and must be replaced with new ones.
Attention! Damaged fasteners (nuts, bolts, studs, washers) must be replaced.
Rusted bolts and nuts are pre-treated with a penetrating compound such as turpentine, kerosene or special liquids and temporarily held before loosening to facilitate removal. In emergency cases, it is allowed to use a chisel or a hacksaw, followed by the removal of fastener residues from the threaded part. flat (lining) and lock washers must always be reinstalled in the same order and in the same manner during reassembly as during disassembly and removal.
Fastener size
When assembling the car, fastening elements are used, made according to the inch system of measures (English system or SAE standard), and more universal - the metric system of measures. For all their similarity, it is not permissible to confuse them (pic. 2.55).
Both metric and standard bolts can be identified by looking at the heads.
Tightening torques for threaded connections provided by the company «BMW-AG», unless they are specifically specified in the technical specifications, are determined depending on the diameter of the thread.
Attention! Below are the data on the maximum permissible tightening torque of standard threaded connections, depending on the size of the thread, the material of the bolt, screw, nut, etc., the color of its surface coating and the strength class set out in BMW internal standard No. 600.02.0.
Maximum tightening torque for connections with M4 thread: | ||
- yellow (ZN) | (8,8) | 2.9 N.m; |
- silver (ZNS) | (8,8) | 2.4 N.m; |
- yellow (ZN) | (10,9) | 4.1 N.m; |
- silver (ZNS) | (10,9) | 3.6 N.m; |
- yellow (ZN) | (12,9) | 4.9 N.m. |
Maximum tightening torque for M5 threaded connections: | ||
- yellow (ZN) | (8,8) | 5.9 N.m; |
- silver (ZNS) | (8,8) | 5.0 N.m; |
- yellow (ZN) | (10,9) | 8.3 N.m; |
- silver (ZNS) | (10,9) | 7.3 N.m; |
- yellow (ZN) | (12,9) | 10.0 N.m; |
- silver (ZNS) | (12,9) | 8.0 N.m. |
Maximum tightening torque for M6 threaded connections: | ||
- yellow (ZN) | (8,8) | 9.9 N.m; |
- silver (ZNS) | (8,8) | 8.6 N.m; |
- yellow (ZN) | (10,9) | 14.0 N.m; |
- silver (ZNS) | (10,9) | 12.6 N.m; |
- yellow (ZN) | (12,9) | 16.5 N.m; |
- silver (ZNS) | (12,9) | 14.0 N.m. |
Maximum tightening torque for M7 threaded connections: | ||
- yellow (ZN) | (8,8) | 14.8 N.m; |
- silver (ZNS) | (8,8) | 14.0 N.m; |
- yellow (ZN) | (10,9) | 21.3 N.m; |
- silver (ZNS) | (10,9) | 20.5 N.m; |
- yellow (ZN) | (12,9) | 25.5 N.m; |
- silver (ZNS) | (12,9) | 22.5 N.m. |
Maximum tightening torque for M8 threaded connections: | ||
- yellow (ZN) | (8,8) | 24.0 N.m; |
- silver (ZNS) | (8,8) | 20.5 N.m; |
- yellow (ZN) | (10,9) | 34.0 N.m; |
- silver (ZNS) | (10,9) | 30.5 N.m; |
- yellow (ZN) | (12,9) | 40.0 N.m; |
- silver (ZNS) | (12,9) | 33.5 N.m. |
Maximum tightening torque for M8x1 threaded connections: | ||
- yellow (ZN) | (8,8) | 26.0 N.m; |
- silver (ZNS) | (8,8) | 22.0 N.m; |
- yellow (ZN) | (10,9) | 36.0 N.m; |
- silver (ZNS) | (10,9) | 32.0 N.m; |
- yellow (ZN) | (12,9) | 44.0 N.m; |
- silver (ZNS) | (12,9) | 35.5 N.m. |
Maximum tightening torque for M10 threaded connections: | ||
- yellow (ZN) | (8,8) | 47.0 N.m; |
- silver (ZNS) | (8,8) | 41.0 N.m; |
- yellow (ZN) | (10,9) | 66.0 N.m; |
- silver (ZNS) | (10,9) | 60.0 N.m; |
- yellow (ZN) | (12,9) | 79.0 N.m; |
- silver (ZNS) | (12,9) | 66.0 N.m. |
Maximum tightening torque for M10x1 threaded connections: | ||
- yellow (ZN) | (8,8) | 54.0 N.m; |
- silver (ZNS) | (8,8) | 44.0 N.m; |
- yellow (ZN) | (10,9) | 75.0 N.m; |
- silver (ZNS) | (10,9) | 65.0 N.m; |
- yellow (ZN) | (12,9) | 91.0 N.m; |
- silver (ZNS) | (12,9) | 72.0 N.m. |
Maximum tightening torque for M12 threaded connections: | ||
- yellow (ZN) | (8,8) | 82.0 N.m; |
- silver (ZNS) | (8,8) | 71.0 N.m; |
- yellow (ZN) | (10,9) | 115.0 N.m; |
- silver (ZNS) | (10,9) | 104.0 N.m; |
- yellow (ZN) | (12,9) | 140.0 N.m; |
- silver (ZNS) | (12,9) | 116.0 N.m. |
Maximum tightening torque for threaded connections M12x1.5: | ||
- yellow (ZN) | (8,8) | 87.0 N.m; |
- silver (ZNS) | (8,8) | 73.0 N.m; |
- yellow (ZN) | (10,9) | 123.0 N.m; |
- silver (ZNS) | (10,9) | 108.0 N.m; |
- yellow (ZN) | (12,9) | 147.0 N.m; |
- silver (ZNS) | (12,9) | 120.0 N.m. |
Maximum tightening torque for connections with M14 thread: | ||
- yellow (ZN) | (8,8) | 130.0 N.m; |
- silver (ZNS) | (8,8) | 112.0 N.m; |
- yellow (ZN) | (10,9) | 180.0 N.m; |
- silver (ZNS) | (10,9) | 165.0 N.m; |
- yellow (ZN) | (12,9) | 220.0 N.m; |
- silver (ZNS) | (12,9) | 185.0 N.m. |
Maximum tightening torque for threaded connections M14x1.5: | ||
- yellow (ZN) | (8,8) | 143.0 N.m; |
- silver (ZNS) | (8,8) | 120.0 N.m; |
- yellow (ZN) | (10,9) | 200.0 N.m; |
- silver (ZNS) | (10,9) | 175.0 N.m; |
- yellow (ZN) | (12,9) | 240.0 N.m; |
- silver (ZNS) | (12,9) | 195.0 N.m. |
Maximum tightening torque for connections with M18 thread: | ||
- yellow (ZN) | (8,8) | 280.0 N.m; |
- silver (ZNS) | (8,8) | 240.0 N.m; |
- yellow (ZN) | (10,9) | 390.0 N.m; |
- silver (ZNS) | (10,9) | 355.0 N.m; |
- yellow (ZN) | (12,9) | 470.0 N.m; |
- silver (ZNS) | (12,9) | 395.0 N.m. |
Maximum tightening torque for threaded connections M18x1.5: | ||
- yellow (ZN) | (8,8) | 313.0 N.m; |
- silver (ZNS) | (8,8) | 265.0 N.m; |
- yellow (ZN) | (10,9) | 440.0 N.m; |
- silver (ZNS) | (10,9) | 385.0 N.m; |
- yellow (ZN) | (12,9) | 527.0 N.m; |
- silver (ZNS) | (12,9) | 430.0 N.m. |
Bolt thread must protrude from nut (except in special cases) 2-3 threads. Cotter pins must not protrude from the slots of the nuts. The ends of the cotter pins must be separated and bent one onto the bolt and the other onto the nut. When assembling, blow the fuel line and brake system drive tubes with compressed air and roll them with a ball of the appropriate diameter. Damaged threads in spars and other fasteners can be repaired using threaded inserts from a wire spiral (pic. 2.56) in the following order:
- drill out the remains of the old bolt (hairpins);
- cut a thread for a wire insert;
- select the insert and screw it flush into the hole;
- break off and remove the tail of the insert.