Service technology, tools and workplace equipment (Audi A3 8L)

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

1 – Strength class 1 or 2
2 – Strength class 5
3 – Strength class 8 4 – Marking of the strength class of metric bolts

Strength class marking of standard hex nuts

Three dots - class 5





Six dots - class 8



Arabic 9 – Hexagonal nut, strength class 9

1 – Strength class 10.9
2 – Strength class 9.8
3 – Strength class 8.8

Dimensions/strength class markings of standard (sae and uss) bolts

G – strength class marking



L – length (in inches)

T – thread pitch (number of threads per inch)

D – nominal diameter (in inches)

Dimensions/Grade Markings for Metric Bolts

P – strength class

L – length (in mm)

T – thread pitch (distance between adjacent turns in mm)

D – nominal diameter (in mm)

Service technology

There are several methods for performing vehicle maintenance and repair procedures, which the reader will find references to in the text of this guide. Following them will make the work of a home mechanic more efficient, will allow the best organization and quality execution of various technical procedures, and will be the key to thorough and complete execution of all work.

Fasteners

Fasteners are nuts, bolts, studs and screws used to connect two or more parts together. When working with fasteners, you must always remember some things. Almost any fastener uses one or another type of locking and locking devices. These can be lock washers, lock nuts, lock flags or thread locking compound. All threaded fasteners used must be absolutely clean and straight, with undamaged threads and unrounded corners of the hexagonal heads onto which the wrench is placed. 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 and must always be replaced with new ones during assembly.



Rusted bolts and nuts should be treated with a special penetrating compound to facilitate unscrewing and to avoid damage before loosening. 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, the compound should be allowed to thoroughly 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.

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 auto body 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 installed 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 standard (also called American or SAE standard) and more universal in the metric system of measures, since, despite the external similarity, they are not interchangeable.



All bolts, both standard and metric, are classified by diameter, thread pitch, and length. For example, a standard 1/2 – 13 x 1 bolt has a half inch in diameter, 13 threads per inch, and is 1 inch long. A metric M12 – 1.75 x 25 bolt has a diameter of 12 mm, a thread pitch of 1.75 mm (distance between adjacent turns) and a length of 25 mm. Both bolts are almost identical in appearance, but are not interchangeable.

In addition to the above features, both metric and standard bolts can be identified by examining the head. For starters, the distance between the flats of a metric bolt head is measured in mm, while a standard bolt is measured in inches (the same is true for nuts). As a result, a standard wrench is not suitable for use with metric fasteners, and vice versa. In addition, most standard bolts usually have radial notches on their heads that determine the maximum allowable tightening force 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 strength class of metric bolts is determined by a digital code. The code numbers are usually cast, as for standard ones, on the head of the bolt (automobiles typically use bolts of strength classes 8.8, 9.8, and 10.9).

Standard nuts can also be distinguished from metric nuts by strength class marks. To identify the strength of standard 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.



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.

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 standard fasteners from metric ones is to measure the thread pitch, or compare the thread with a uniquely identified one.

Standard fasteners are often referred to as SAE standard fasteners, as opposed to metric fasteners, but it should be remembered that only small fasteners fall under the SAE classification. Large fasteners with non-metric threads are American Standard Fasteners (USS).

Since the fasteners are of the same geometric size (both standard and metric) may have different strength classes; when replacing bolts, nuts and studs on a vehicle, attention should be paid to ensuring that the strength class of the new fasteners being installed matches the strength class of the old ones.

Procedure and order of tightening threaded connections

Tightening of most threaded connections should be carried out with forces determined by the requirements of the Specifications given 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). Below, the tightening force will also be called the tightening torque of the fastener. Tightening with excessive force can lead to damage to the integrity of the fastener, while undertightening it leads to unreliability of the connection of the mating components. Bolts, screws and studs, depending on the material from which they are made and the diameter of the threaded part, usually have strictly defined permissible tightening torques, many of which, as mentioned above, are given in the Specifications at the beginning of each Chapter. Strictly adhere to the recommendations for tightening torques for the fasteners used on the vehicle. To tighten fasteners not mentioned in the Specifications, use the permissible torque chart below. 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.

Metric Thread Sizes

M–6 9 –12 N.m

M–8 19 – 28 Nm

M–10 38 – 54 Nm

M–12 68 – 96 Nm

M–14 109 – 154 Nm

Pipe thread sizes

1/8 7 –10 Nm

1/4 17 – 24 Nm

3/8 30 – 44 Nm

1/2 34 – 47 Nm

American Standard Thread Sizes

1/4 – 20 9 – 12 N.m

5/16 – 18 17 – 24 N.m

5/16 – 24 19 – 27 N.m

3/8 – 16 30 – 43 Nm

3/8 – 24 37 – 51 N.m

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 bolts, oil pan bolts and various covers), to avoid distortion of the component, the fastener must be loosened and tightened in a strictly defined order. The tightening and loosening order for such fasteners is given in the relevant Chapters of the Manual. Unless a special order is specified, the following procedure must be followed to avoid distortion of the component. In the first stage, all bolts or nuts must be tightened by hand. Next, each of them in turn must be tightened another full turn, with the transition from one bolt/nut to the next being carried out in a diagonal order (criss-cross). Then, returning to the first bolt/nut, the procedure must be repeated in the same order, tightening the fastener another half-turn. Continue to act in the same manner, tightening each bolt/nut this time by a quarter of a turn at a time until they are all tightened to the required force. When loosening the fasteners, the described procedure must also be followed, but acting in reverse order.

Disassembling the components

Disassembly of all components must 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 work 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 removed.



When removing fasteners, try to mark their original position on the assembly. Often, immediately installing fasteners and washers in their original place 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 sections and marked accordingly, or simply in separate marked boxes. This procedure is especially useful when working with components consisting of many small parts, such as a carburetor, generator, valve mechanism, instrument panel or decorative trim elements.

When disconnecting electrical contacts and connectors, pay attention to marking the wires or harnesses with insulating tape with a digital 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.

Often such gaskets are coated with a liquid or paste-like sealing compound before installation. Often, under the influence of time, temperature or pressure, the mating surfaces "stick" to each other so strongly that separating the parts becomes a difficult task. In many cases, dismantling such assemblies is helped 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 and fragile components. If such difficulties arise, always first check whether all fasteners have been removed.

Avoid using a screwdriver or pry bar to separate parts by inserting them between mating surfaces, as the sealing surfaces can easily be damaged, which can later cause leaks. If it is impossible to avoid levering "stuck" assembly elements, use the handle of an old broom for this purpose, but remember that all splinters that form must be carefully removed from the mating surfaces and from inside the assembly.

After separating the parts, their mating surfaces should be thoroughly cleaned, scraping off any traces of the old gasket material. Hardened fragments of the old gasket can be softened in advance with a rust converter or special chemical compound, and then removed from the mating surface with a scraper. 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 gasket should be used (or semi-hardening) sealant.

Tips for removing hoses

Warning: If your vehicle is equipped with an air conditioning system, do not disconnect any hoses from the air conditioning components under any circumstances until the system has been discharged by an AUDI dealer or an air conditioning specialist at an automotive service center.

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 placed, as this may cause leaks. This applies especially to the procedure for removing radiator hoses. Various chemical reactions cause the rubber of the hoses to "stick" 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/connecting 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 case of a clear need to replace the hose with a new one, the end of the hose put on the nipple for removal can be cut with a knife and then separated from the surface of the nipple. In this case, try not to damage the metal of the nipple/under the connecting pipe with the knife.

If the hose clamp is damaged, replace it with a new one. 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 and simple repairs to a car at a service station, they will be quite reasonable.

To assist the average car owner in selecting the tools needed to perform the various car maintenance procedures described in this manual, the following are lists of three tool kits, conventionally titled: Routine Maintenance and Minor Repair Tool Kit; a set of tools for general and major repairs and a special tool. Car owners who do not have practical experience in mechanical work should start with performing 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 performing more complex tasks, supplementing the set of tools you have 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 begin to allow you to save significant funds by independently performing complex repair procedures, 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.

• Combination Key Set (1/4-1 inch; 6-19 mm)
• Adjustable wrench
• Spark plug wrench (with rubber insert)
• Spark plug gap adjustment tool
• Set of measuring probes
• Brake Bleeding Nipple Key
• Screwdrivers:
• With a flat tip (150mm long and 8mm in diameter)
• With cross stinger (# 2 x 6 inches (150 mm long)
• Combination pliers
• Hacksaw for metal with a set of blades
• Tire pressure gauge
• Grease gun (syringe)
• Oil canister
• Fine 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 pcs
• Drainage tank

Warning: If routine maintenance procedures include performing basic adjustments, you will also need to purchase a good quality strobe light and a combined tachometer / instrument to measure the duration of the closed state of the breaker contacts. Despite the fact that these tools are included in the list of special tools, they are mentioned here in view of the absolute necessity of their use for high-quality tuning of the engine ignition, which is part of the car's routine maintenance procedures.

A set of tools for general and major car repairs

This tool is essential for any car engine repair work and is offered in addition to the first list. This list includes a complete set of interchangeable socket heads. Despite the considerable cost, the set of interchangeable heads brings invaluable benefits due to its 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.

Set of replacement socket heads (including Torx type heads) (or tubular wrenches), sizes corresponding to the sizes of wrenches from the previous list.

• Ratchet reversible drive (for use with interchangeable socket heads)
• Gate length 250 mm
• Universal (cardan type) hinge (for use with socket heads)
• Torque wrench (with the same size drive as for socket heads)
• 8 oz Round Peen Hammer (about 230 g)
• Soft-faced hammer (plastic or rubber)(mallet)
• Screwdrivers:
• With a flat tip (150 mm long and about 6.5 mm in diameter)
• With flat tip (strong No.2, 8 mm)
• With cross blade (No. 3 x 8 inches (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)
• 1/2 inch (13 mm) chisel
• 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)
• Steel ruler/flatness gauge
• Set of Allen keys (Allen) (for hexagon socket heads)
• Set of files
• Wire brush (large)
• Second set of supports
• Jack (hydraulic or scissor type)

Warning: Another tool that is constantly needed is a 3/8-inch (up to 9.5 mm) electric drill with a set of good quality drills.

Special tool

This list includes tools that are quite expensive, not needed regularly, or require following the manufacturer's instructions when using. 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 produced for distribution to dealer branches of companies. Sometimes in the text of the Manual you will 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 car service specialists.

• Valve Spring Compressor 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 (micrometers) and/or dial caliper
• Hydraulic tappet removal tool
• Ball joint separator
• Universal type puller
• Impact screwdriver
• Dial Gauge Set
• Stroboscope (with inductive sensor)
• Hand Combination Pump (vacuum/pressure)
• Tachometer/breaker contact duration measuring instrument
• Universal tester for electrical measurements
• Lifting rigging
• Tool for removing/installing brake springs
• Floor jack

Micrometer with a set of attachments



Dial gauge with a set of clamps and attachments



Dial/Vernier Caliper



Hand operated vacuum pump



Stroboscope



Compression gauge with spark plug hole attachment



Damper/Steering Wheel Remover



General purpose puller



Hydraulic tappet removal tool



Valve Spring Compressor Tool



Valve Spring Compressor Tool



Countersink for removing stepped wear in a cylinder



Piston Ring Groove Cleaning Tool



Piston ring removal/installation tool



Piston Ring Crimping Tool



Hone for processing cylinder mirrors



Tool for removing brake shoe guide spring cups



Hone for processing brake cylinders



Clutch Disc Centering Tool



Set of taps and dies

Purchasing a tool

A novice mechanic can be offered several practical tips in terms of purchasing the necessary tools for performing routine maintenance and repair procedures of a car. When preparing to perform routine maintenance procedures or minimal repairs of a car, it is reasonable to purchase tools separately. On the other hand, in case of planning extensive work, it is easier and more reliable to buy a set of modern tools in a retail store. Purchasing a set is usually somewhat cheaper than individual purchases and is often supplemented by an attached tool box. In the future, to expand the choice, individual tools, additional sets and a larger tool box can be purchased. Gradually expanding the set of tools will allow you to stretch out the costs and decide on the choice of the really necessary tools.

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 the tool, before storing it, always wipe its surface thoroughly with a clean, dry cloth, removing traces of dirt, grease and metal particles. Never leave the tool 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 dry, clean, and corrosion-proof places.


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 and attention to remove riveting with sandpaper or a file and tidy up the cutting edges. Replace irreversibly worn or damaged tools.

With careful care, the instrument will serve you faithfully for a very long time.

Workplace equipment

When talking about tools, we cannot forget about the equipment of the workplace. If more serious work than simple maintenance is to be carried out, it is necessary to take care of the preparation of a suitable work site.

It must be admitted that many car enthusiasts are forced to remove the engine and other similar work far from a garage or workshop. However, in any case, an important requirement is the presence of a roof or awning.

If possible, any procedures for disassembling parts of vehicle systems should be performed on a clean, flat workbench or a sturdy table of a comfortable height. The workbench must be equipped with a vice. A vice with a jaw opening of up to 100 mm and with soft pads on the jaws is sufficient.

As mentioned above, the work site should be equipped with a clean, dry place for storing tools, lubricants and cleaning fluids, putties, paints and varnishes, etc.

It should be noted that an absolutely necessary tool is an electric drill, therefore, the work site must be equipped with a power source for its connection. Having a drill with a chuck up to 9.5 mm and a set of high-quality drills will greatly facilitate the implementation of many procedures.

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.

Waste must be delivered to recycling centers in sealed containers.

Never do any work on the uncovered painted surface of the car, use protective pads on the fenders, or, at worst, cover the polished surfaces with old blankets.

The original article is available on the online resource: AUDIMANUAL