Service technology, tools and workplace equipment (BMW 7 Series E38)

Service technology

There are several methods for performing vehicle maintenance and repair procedures, which the reader can find references to in the text of this Manual. Following them will make the work more efficient, allow the workplace to be organized in the best possible way, and various technical procedures to be performed efficiently.

Fasteners

Fasteners are nuts, bolts, studs and screws used to connect two or more parts. When working with fasteners, you should always remember some things. Almost any fastener uses one or another type of locking and fixing devices. These can be lock washers, lock nuts, lock flags or thread locking compound. All threaded fasteners used must be absolutely clean and smooth, with undamaged threads and unrounded corners of the hexagonal heads onto which the wrench is put on. It is a rule to replace damaged nuts and bolts with new ones. Special self-locking nuts with nylon or fiber inserts cannot be reused, since they lose their locking properties when loosened.

Rusted bolts and nuts should be treated with a special penetrating compound to make them easier to loosen and to avoid damaging them. Many mechanics prefer to use turpentine for this purpose, which is conveniently applied from a special small canister with a long spout. After wetting the "stuck" fastener with the penetrating compound, before starting to loosen it, let the compound soak the oxidized contact layer for several minutes. Heavily rusted fasteners can be cut off with a chisel, sawed off with a hacksaw, or removed with a special nut splitter.



Threaded connections that are subject to large temperature changes (for example, EGR valve, lambda probe, exhaust manifold), tend to weld, making removal difficult during subsequent maintenance. To facilitate loosening of such fasteners, lubricate them with Molycote 1000 30 20 971 or Never Seize before tightening.

When a bolt head is sheared off or a stud is broken off on an assembly, the remaining threaded portion can be drilled out or extracted with a special tool. Most mechanics and auto repair shops can undertake this and other (for example, restoration of stripped threads in threaded holes), repair procedures.

When reassembling, flat and lock washers should always be reinstalled in the same order and manner as before. Always replace damaged washers with new ones. Between the lock washer and the soft metal surface (for example, aluminum), when using thin sheet metal or plastic, always use flat washers.

Fastener dimensions

For many reasons, vehicle manufacturers are increasingly using metric fasteners. However, it is important to know the difference between the SAE standard fasteners that are sometimes used (also called American) and more universal in the metric system of measures, since, despite the external similarity, they are not interchangeable.

All bolts, both SAE and metric, are rated by diameter, thread pitch, and length. For example, an SAE 1/2-13x1 bolt is half an inch in diameter, has 13 threads per inch, and is 1 inch long. A metric M12-1.75x25 bolt is 12 mm in diameter, has a 1.75 mm thread pitch, and is 25 mm long. Both bolts are virtually identical in appearance, but are not interchangeable.



In addition to the above features, bolts can be identified by examining their heads. The distance between the flats of a metric bolt head is measured in mm, while that of an SAE bolt is measured in inches (the same is true for nuts). As a result, an SAE standard wrench is not suitable for use with metric fasteners, and vice versa.

Dimensions/Grade Markings of SAE and USS Standards



Dimensions/Grade Markings for Metric Bolts



Additionally, most SAE bolt heads typically have radial notches on them that indicate the maximum allowable tightening torque of the bolt (degree of strength). The greater the number of notches, the higher the permissible force (cars typically use bolts with a strength rating of 0 to 5). The property class of metric bolts is determined by a numerical code, which is usually cast on the head of the bolt.



Marking of the strength class of bolts (top - standard /SAE/USS, bottom - metric)



Also, SAE nuts can be distinguished from metric nuts by strength class marks. To identify the strength of SAE nuts, dot marks are used, stamped on one of the end surfaces of the nut, while metric nuts are marked using numbers again. The greater the number of dots, or the higher the value of the digital code, the higher the permissible tightening force of the nut.

SAE Standard Hex Nut Strength Class Markings

Class Identification



Class Identification





Metric Hex Nut Strength Class Markings

Class Identification



Class Identification



The ends of metric studs are also marked according to their strength class. Large studs are marked with a digital code, while smaller ones are marked with a geometric figure.

Marking the strength class of metric studs





It should be noted that a significant portion of fasteners, especially those of strength class 0 to 2, are not marked at all. In this case, the only way to distinguish SAE standard fasteners from metric ones is to measure the thread pitch, or compare the thread with the standard.

Since fasteners of the same geometric size can have different strength classes, when replacing bolts, nuts and studs on a vehicle, attention should be paid to the compliance of the strength class of the new fastener being installed with the strength class of the old one.

Procedure and order of tightening threaded connections

Most threaded connections should be tightened to the torques specified in the Specifications provided at the beginning of each chapter of this Manual (the tightening force of a fastener should be understood as the torque applied to it when tightening). Overtightening can result in failure of the fastener, while undertightening can result in unreliable connections between the mating components. Bolts, screws and studs, depending on their material and thread diameter, usually have strictly defined permissible tightening forces, many of which, as mentioned above, are listed in the Specifications at the beginning of each chapter. For tightening fasteners not listed in the Specifications, the following chart of permissible torques should be used. The values given in the table are oriented towards fasteners of strength classes 2 and 3 (higher grade fasteners allow for greater tightening force), in addition, it is implied that dry tightening is carried out (with ungreased threads) fasteners in steel or cast (not aluminum) detail.

Tightening forces for metric threads

M6	9 — 12 Nm
M8	19 — 28 Nm
M10	38 — 54 Nm
M12	68 — 96 Nm
M14	109 — 154 Nm

Tightening forces of pipe threads

1/8	7 - 10 Nm
1/4	17 — 24 Nm
3/8	30 — 44 Nm
1/2	34 — 47 Nm

SAE and USS thread tightening forces

1/4 — 20	9 — 12 Nm
5/16 — 18	17 — 24 Nm
5/16 — 24	19 — 27 Nm
3/8 — 16	30 — 43 Nm
3/8 — 24	37 — 51 Nm
7/16 — 24	55 — 74 Nm
7/16 — 20	55 — 81 Nm
1/2 — 13	75 — 108 Nm

A fastener located around the perimeter of a part (such as cylinder head mounting bolts, oil pan and various covers), to avoid deformation of the part, it is necessary to loosen and tighten it in a strictly defined order, as described in the relevant chapters of the Manual. If this order is not specified, then to avoid distortion of the component, the following procedure should be followed. In the first stage, tighten all bolts or nuts by hand. Then tighten each fastener element in turn by one more full turn, and the transition from one bolt/nut to another should be carried out in a diagonal order (criss-cross). Next, return to the first bolt/nut and repeat the procedure in the same order, tightening the fastener another half turn. Continue in the same manner, tightening each bolt/nut this time by a quarter turn at a time until they are all tightened to the required force. When loosening the fastener, you should also follow the described procedure, but in reverse order.

Disassembling the components

Disassembly of all components should be carried out in such a manner that during assembly each part can be installed in its original place and in the correct way. Remember the characteristic features of the appearance, if necessary, make a landing marking of parts, the installation of which in place can be carried out in an ambiguous way (such elements include, for example, a grooved thrust washer on the shaft). It is a good idea to lay out the removed parts on a clean surface in the order in which they were removed. It may also be helpful to make simple schematic drawings or take step-by-step photographs of the component to be disassembled or removed.

When removing fasteners, try to mark their original position on the assembly. Often, immediately replacing fasteners and washers in their original position after removing the corresponding part helps to avoid confusion during assembly. If this is not possible, all fasteners should be placed in a specially prepared box divided into marked sections, or simply in separate marked containers. This procedure is especially useful when working with components consisting of many small parts, such as an alternator, valve mechanism, instrument panel, or interior trim elements.

When disconnecting electrical contacts and connectors, individual wires or wiring harnesses should be marked with insulating tape with a numerical or letter code applied to it.

Gasket surfaces

On all vehicles, gaskets are used to seal the junction of the mating surfaces of two or more parts and serve to prevent oil and fluid leaks and maintain increased pressure or vacuum inside the assembly.

Typically, such gaskets require a liquid or paste-like sealing compound before installation. Often, under the influence of time, temperature or pressure, the mating surfaces become so strongly "stuck" to each other that separating the parts becomes difficult. Disassembling such units is aided by tapping them from the outside along the perimeter of the joint with a soft-faced hammer. You can also use a regular hammer for this purpose, striking through a wooden or plastic spacer. Do not tap cast housings or fragile components. If such difficulties arise, always first check that all fasteners have been removed. Try not to use a screwdriver or crowbar to separate the parts, inserting them between the mating surfaces can easily damage them, which can later cause leaks. If it is impossible to avoid levering the "stuck" assembly elements, use a wooden handle from an old broom for this purpose, but do not forget to carefully remove all the splinters that have formed from the mating surfaces and from inside the assembly.

After separating the parts, their mating surfaces should be thoroughly cleaned, scraping off the old gasket material. Hardened fragments of the old gasket can be softened with a rust converter or special chemical compound before being scraped off. In this case, a piece of copper tubing with a flattened and sharpened end can be used as a scraper. It is recommended to use a copper tube for this purpose, since copper is usually softer than the materials used in the car, which reduces the risk of damaging the mating surface. Some gaskets can be easily removed with a copper brush, but regardless of the method used, the mating surfaces must be completely clean and smooth. If for any reason the mating surface is scratched, fill the scratch with gasket sealant before assembling the components. In most cases, a non-hardening or semi-hardening sealant should be used.

Tips for removing hoses

Do not disconnect any hoses from the air conditioning (A/C) system components until the system has been discharged by a qualified service technician.

The precautions to be taken when removing hoses are very similar to those for removing gaskets. Avoid damaging the surfaces of the fittings and pipes onto which the hoses are put on, as this may cause leaks. This applies especially to the procedure for removing the hoses of the cooling system. Due to various chemical reactions, the rubber of the hoses "sticks" to the mating surfaces of the fittings and pipes. To remove a hose, first loosen the clamp securing it to the fitting. Then, using pliers with a sliding joint, grasp the hose near the clamp and begin to rotate it on the fitting or pipe to the right and left. Continue this procedure until the hose is completely free, then remove the hose from the fitting. A small amount of silicone or other grease will facilitate the procedure if it can be introduced into the gap between the fitting and the hose. To facilitate the installation of the hose, lubricate the inner surface of the hose and the outer surface of the fitting.

As a last resort, or in the case of a clear need to replace the hose, you can cut the end of the hose with a knife to remove it from the nipple. In doing so, try not to damage the metal of the nipple or connecting pipe with the knife.

If the hose clamp is damaged, replace the clamp. Twist-type clamps tend to loosen over time, so regardless of their condition, it is best to replace them with screw-type clamps when necessary.

Tool

Selecting a good tool is one of the basic requirements for anyone planning to perform maintenance or repair procedures on their own. At first glance, the costs associated with purchasing the required set of tools may seem too high, but when compared with the costs associated with performing routine maintenance procedures and simple car repairs at a service station, they will be quite reasonable.

Lists of three tool kits are provided below. Car owners who do not have practical experience in mechanical work should start with procedures limited to the use of tools from the first list, while improving their skills and gradually expanding the range of tools used. As experience is gained, you can move on to more complex tasks, supplementing the existing set of tools on hand. After some time, the acquired skills will allow you to begin performing more complex work requiring the use of tools from the second list (for general and major repairs of the car). When your skills allow you to save significant amounts of money by performing complex repair procedures on your own, you can think about purchasing a special tool.

A set of tools for routine maintenance and minimal repairs of a car

The list below includes the minimum tools needed to perform routine maintenance and minor repairs on your vehicle. It is recommended that you purchase a set of combination wrenches (with a regular open-end head on one end and a socket head on the other). Despite the higher cost of such a set compared to the cost of a set of conventional open-end wrenches, the costs will be justified, since these wrenches have the advantages of both types.

• Set of combination wrenches from 8 to 19 mm
• Adjustable wrench (up to 35 mm)
• Spark plug wrench with rubber insert (petrol models)
• Spark plug gap adjustment tool (petrol models)
• Set of measuring probes
• Brake Bleeding Nipple Key
• Screwdrivers:
• With a flat tip (100mm long by 6mm in diameter)
• With a cross sting (100mm long by 6mm in diameter)
• Combination pliers
• Hacksaw for metal with a set of blades
• Tire pressure gauge
• Grease gun (syringe)
• Oil canister
• Fine grit sandpaper
• Wire brush
• Tool for stripping terminals and contacts of battery wires
• Oil filter removal key
• Funnel (medium size)
• Supports for fixing the car in a raised position (2)
• Drainage tank

A set of tools for general and major car repairs

The following tools are required when repairing a car engine and are offered in addition to the first list. This list includes a complete set of interchangeable socket heads. Despite the considerable cost, a set of interchangeable heads brings invaluable benefits due to their versatility and ease of use - especially in combination with the various types of drives included in the set. It is recommended to use preferably 1/2 inch drives (and not 3/8 inch), because they, although more expensive, can be used with almost any type of torque wrench (ideally, a good mechanic should have both types of drives at his disposal). A cheaper alternative to a set of socket heads is a set of tubular wrenches.

• A set of replacement socket heads (including Torx heads) or tubular wrenches, sizes corresponding to the sizes of the wrenches from the previous list
• Ratchet reversible drive (for use with interchangeable socket heads)
• Gate length 250 mm
• Cardan drive (for use with interchangeable socket heads)
• Torque wrench (with the same size drive as for socket heads)
• Self-locking pliers
• Round-head hammer (about 230 g)
• Soft-faced hammer (plastic or rubber)
• Screwdrivers:
• With a flat tip (150 mm long and about 6.5 mm in diameter)
• With flat tip (strong No.2, 8 mm)
• With a cross blade (No. 3, 203 mm)
• With a cross blade (strong No.2)
• Clamping pliers
• Pliers:
• For electricians (with insulated handles)
• Narrow-nosed (needle nose pliers)
• For retaining rings (internal and external)
• Chisel 25 mm
• Scraper (made from a copper tube flattened and pointed at one end)
• Scriber (scribe)
• Kerner
• Beards with a thin sting (1.6, 3.2, 4.8 mm)
• Hose clamp kit
• Brake Bleeding Kit
• Set of drills
• Steel ruler/flatness gauge
• Set of Allen keys (for hexagon socket heads)
• Set of files
• Wire brush (large)
• Second set of supports
• Jack (hydraulic or foot type)

Another constantly required tool is an electric drill with a chuck up to 9.5 mm and a set of high-quality drills.

Special tool

This list includes tools that are quite expensive, not needed regularly, or require following the manufacturer's instructions when using them. If your area of activity does not include frequent complex mechanical operations, purchasing such a tool will be a bad investment. It is reasonable to buy it together with friends or rent it from auto repair shops.

The list includes only those tools that can be found in retail or that are issued for distribution to representative offices of companies. Sometimes in the text of the Manual you can find references to such special tools. Usually the authors try to simultaneously offer an alternative method that allows you to avoid the mandatory use of a hard-to-find tool. If it is impossible to avoid using a special tool, and acquiring it for use is problematic, it is better to entrust the performance of the relevant work to service station specialists.

• Valve Spring Compressor Tool
• Valve grinding tool
• Piston Ring Groove Cleaning Tool
• Piston Ring Crimping Tool
• Piston Ring Installation Tool
• Cylinder Compression Gauge (compression meter)
• Countersink for processing cylinder edges
• Hone for processing cylinder mirrors
• Cylinder Bore Gauge
• Micrometer and/or dial caliper
• Clutch Disc Centering Tool
• Ball joint puller
• Universal type puller
• Impact screwdriver
• Dial Gauge Set
• Stroboscope (with inductive sensor)
• Hand Combination Pump (vacuum/pressure)
• Set of taps and dies
• Tachometer/breaker contact duration measuring instrument
• Universal tester for electrical measurements
• Lifting rigging
• Tool for removing/installing brake springs
• Trolley jack

Purchasing a tool

When preparing to perform routine maintenance or minimal repairs to a vehicle, it is reasonable to purchase tools individually. On the other hand, if you are planning extensive work, it is simpler, more reliable and more cost-effective to buy a set of modern tools, which usually comes with a toolbox. Later, to expand your selection, you can purchase individual tools, additional sets and a larger toolbox. Gradually expanding your toolbox will help you spread out your expenses and decide on the choice of tools that are truly necessary.

Specialty tool stores are the only source for some specialty tools, but regardless of the source, avoid cheap purchases, especially when choosing screwdrivers and socket heads, as their service life is likely to be short. The costs associated with replacing and restoring a cheap tool will ultimately be incomparably greater than the cost of a one-time purchase of a quality product.

Care and storage of the instrument

A good tool is a valuable investment, so it is wise to take care to keep it clean and always ready for use. After using a tool, always thoroughly clean it of dirt, grease and metal particles before storing it. Never leave tools scattered around the work area. After completing work, carefully check the space under the hood and under the car for forgotten tools.

A tool rack mounted in a convenient place on the garage wall is ideal for storing tools such as screwdrivers, pliers, hammers, etc. Sets of wrenches and socket heads should be stored in metal boxes. Measuring tools should be stored in places that are free from corrosion, dry, and clean.

You should always pay attention to the condition of the working surfaces of the tool. The striking part of the hammer head is subject to riveting during work, screwdrivers lose the sharpness of their tips over time. Do not skimp on spending a little time on removing rivets and tidying up the cutting edges with sandpaper or a file. Replace irreversibly worn or damaged tools.

With proper care, the instrument will last for a very long time.

Workplace equipment

If more serious work than simple routine maintenance is to be carried out, care should be taken to prepare a suitable work area. An important requirement is the presence of a roof or awning.

If possible, any disassembly procedures should be carried out on a clean, flat workbench (table) of a comfortable height, equipped with a vice. It is sufficient to have a vice with soft pads on the jaws, opening up to 100 mm.

As mentioned above, the work site should have a clean, dry place for storing tools, lubricants, cleaners, putties, paints and varnishes, etc.

Since an electric drill is an absolutely necessary tool, the work site must therefore be equipped with a power source to connect it.

Finally, the workplace should always have an adequate supply of old newspapers and clean, lint-free rags available for cleaning the work area, tools, and vehicle parts.

Never do any work on the exposed painted surface of the car, use protective fender covers or cover polished surfaces with old blankets.