1962-1980 MG MGB Service & Repair Manual

66010 utomotive Repair Manual

MGB Automotive Repair Manual John Fowler Models covered All models of the MGB Roadster and GT Coupe with 1798 cc (110 cu in) engine Does not cover MGB GT \i8 ISBN 0 85696 6231 HR1"n~~!'I North America, Inc. 1981,1987,1989 Wilh permission from J. H. Haynes & Co. Lid. All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electrical or mechanical, including photocopying, recording or information storage or retrieval system, without permission in writing from the copyright Printed in the USA (6/=4 - 66010) Haynes Publishing Group Sparkford Nr Yeovil Somerset BA22 7 JJ England Haynes North America, Inc 861 Lawrence Drive Newbury Park California 91320 USA 1

Acknowledgements Thanks are due to the Champion Sparking Plug Company Limited who supplied the illustrations sAowing spark plug conditions, to Holt Lloyd Limited who supplied the illustrations showing bodywork repair, and to Duckhams Oils who provided lubrication data. Thanks are also due to Rover cars for supplying technical information. The Section in Chapter 10 dealing with the suppression of electrical interference was originated by Mr. I. P. Davey and was first published in Motor magazine. © Haynes North America, Inc. 1981,1987,1989 With permission from J. H. Haynes & Co. Ltd. A book in the Haynes Automotive Repair Manual Series Printed in the USA All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage or retrieval system, without permission in writing from the copyright holder. ISBN 0 85696 623 1 Whilst every care is taken to ensure that the information in this manual is correct. no liability. can be accepted by the authors or publishers for loss, damage or injury caused by any errors in, or omis- sions from, the information given.

Contents Page Acknowledgements 2 About this manual 4 Introduction to the MGB 4 Use of English 6 Buying spare parts and vehicle identification numbers 7 Tools and working facilities 8 Jacking and towing 10 Recommended lubricants and fluids 11 Safety first! 12 Routine maintenance 13 Fault diagnosis 16 Chapter 1 Engine 20 Chapter 2 Cooling system 55 Chapter 3 Fuel, exhaust and emission control systems 65 Chapter 4 Ignition system 94 Chapter 5 Clutch 106 Chapter 6 Gearbox, overdrive and automatic transmission 111 Chapter 7 Propeller shaft 138 Chapter 8 Rear axle 142 Chapter:3 Braking system 146 Chapter 10 Electrical system 161 Chapter 11 Suspension and steering 202 Chapter 12 Bodywork and fittings 215 Conversion factors 240 Index 241

About this manual Its aim The aim of this manual is to help you get the best value from your car. It can do so in several ways. It can help you decide what work must be done (even should you choose to get it done by a garage), provide information on routine maintenance and servicing, and give a logical course of action and diagnosis when random faults occur. However, it is hoped that you will use the manual by tackling the work yourself. On simpler jobs it may even be quicker than booking the car into a garage' and going there twice to leave and collect it Perhaps most important, a lot of money can be saved by avoiding the costs the garage must charge to cover its labour and overheads. The manual has drawings and descriptions to show the function of the various components so that their layout can be understood. Then the tasks are described and photographed in a step-by-step sequence so that even a novice can do the work. Its arrangement The manual is divided into twelve Chapters, each covering a logical sub-division of the vehicle. The Chapters are each divided into Sections, numbered with single figures, eg 5; and the Sections into paragraphs (or sub-sections), with decimal numbers following on from the Section they are in, eg 5.1, 5.2, 5.3 etc. Introduction to the MGB Since first introduced, the MGB had undergone many modifications as a result of development, and in order to comply with regulations which have come into force in certain territories. The engine, of straightforward design, began as a three-main bearing unit, but a five-main bearing version was subsequently developed. The transmission system is available in various versions, and can be a four-speed manual gearbox, a four-speed manual gearbox with overdrive, or an automatic gearbox. Independent front suspension is employed, together with rubber- mounted semi-elliptical springs at the rear. It is freely illustrated, especially in those parts where there is a detailed sequence of operations to be carried out. There are two forms of illustration: figures and photographs. The figures are numbered in sequence with decimal numbers, according to their position in the Chapter - eg Fig. 6.4 is the fourth drawing/illustration in Chapter 6. Photographs carry the same number (either individually or in related groups) as the Section or sub-section to which they relate. There is an alphabetical index at the back of the manual as well as a contents list at the front. Each Chapter is also preceded by its own individual contents list References to the 'left' or 'right' of the vehicle are in the sense of a person in the driver's seat facing forwards. Unless otherwise stated, nuts and bolts are removed by tuming anti- clockwise, and tightened by turning clockwise. Vehicle manufacturers continually make changes to specifications and recommendations, and these when notified are incorporated into our manuals at the earliest opportunity. Whilst every care is taken to ensure that the information in this manual is COlTect. no liability can be accepted by the authors or publishers for loss. damage or injury caused by any elTors in, or omissions from. the information given. Depending upon the model, a three-quarter floating or semi-floating rear axle is fined, driven by a propeller shaft and universal joints. A hydraulically-operated diaphragm spring clutch is fined to all models which employ manual transmission. Disc front brakes and drum rear brakes are fined, hydraulically operated. Servo assistance, and a tandem brake master cylinder, are fined as appropriate to certain veh icles. The cable-operated handbrake is applied to the rear wheels only. Vehicles manufactured for certain territories are fined with exhaust emission control systems, in order that the amount of poisonous exhaust gases being released afe reduced to tl=1e permined level.

Use of English As this book has been written in England. it uses the appropriate English component names, phrases, and spelling. Some of these differ from those used in America. Normally, these cause no difficulty, but to make sure, a glossary is printed below. In ordering spare parts remember the parts list may use some of these words: . English American English American Accelerator Gas pedal Locks Latches Aerial Antenna Methylated spirit Denatured alcohol Anti-roll bar Stabiliser or sway bar Motorway Freeway, turnpike etc Big-end bearing Rod bearing Number plate License plate Bonnet (engine cover) Hood Paraffin Kerosene Boot (luggage compartment) Trunk Petrol Gasoline (gas) Bulkhead Firewall Petrol tank Gas tank Bush Bushing 'Pinking' 'Pinging' Cam follower or tappet Valve lifter or tappet Prise (force apart) Pry Carburettor Carburetor Propeller shaft Driveshaft Catch Latch Quarterlight Quarter window Choke/venturi Barrel Retread Recap Circlip Snap-ring Reverse Back-up Clearance Lash Rocker cover Valve cover Crownwheel Ring gear (of differential) Saloon Sedan Damper Shock absorber, shock Seized Frozen Disc (brake) Rotor/disk Sidelight Parking light Distance piece Spacer Silencer Muffler Drop arm Pitman arm Sill panel (beneath doors) Rocker panel Drop head coupe Convertible Small end, little end Piston pin or wrist pin Dynamo Generator (DC) Spanner Wrench Earth (electrical) Ground Split cotter (for valve spring cap) Lock (for valve spring retainer) Engineer's blue Prussian blue Split pin Cotter pin Estate car Station wagon Steering arm Spindle arm Exhaust manifold Header Sump Oil pan Fault finding/diagnosis Troubleshooting Swar' Metal chips or debris Float chamber Float bowl Tab washer Tang or lock Free-play Lash Tappet Valve lifter Freewheel Coast Thrust bearing Throw-out bearing Gee'box Transmission Top gear High Gearchange Shift Torch Flashlight Grub screw Setscrew, Allen screw Trackrod (of steering) Tie-rod (or connecting rod) Gudgeon pin Piston pin or wrist pin Trailing shoe (of brake) $econdary shoe Halfshaft Axleshaft Transmission Whole drive line Handbrake Parking brake Tyre Tire Hood Soft top Van Panel wagon/van Hot spot Heat riser Vice Vise Indicator Turn signal Wheel nut Lug nut Interior light Dome lamp Windscreen Windshield Layshaft (of gearbox) Countershaft Wing/mudguard Fender Leading shoe (of brake) Primary shoe

Buying spare parts and vehicle identification numbers Buying spare parls Replacement parts are available from many sources, which generally fall into one of two categories - authorized dealer parts departments and independent retail auto parts stores. Our advice conceming these parts is as follows: Retail auto parts stores: Good auto parts stores will stock frequently needed components which wear out relatively fast, such as clutch compo- nents, exhaust systems, brake parts, tune-up parts, etc. These stores of- ten supply new or reconditioned parts on an exchange basis, which can save a considerabre amount 01 money. Discount auto parts stores are 01- ten very good places to buy materials and parts needed for general vehicle maintenance such as oil, grease, filters, spark plugs, belts, tOUCh-Up paint, bulbs, etc. They also usually sell tools and general accessories, have con- venient hours, charge lower prices and can often be found notlar from home. Authorized dealer parts department: This is the best source for parts which are unique to the vehicle and not generally available elsewhere (such as major engine parts, transmission parts, trim pieces, etc.). Warranty information: If the vehicle is still covered under warranty, be sure that any replacement parts purchased - regardless of the source- do not invalidate the warranty! To be sure 01 obtaining the correct parts, have engine and chassis numbers available and, if possible, take the old parts along for positive identification. Vehicle identification numbers Modifications are a continuing and unpublished process in vehicle manufacture quite apart from major model changes. Spare parts manuals and lists are compiled upon a numerical basis, the individual vehicle num- bers being essential to correct identification of the component required. The position of the numbers concerned has varied, but the following list gives some guidance. The car will have an identification plate, normally found on the inside of one of the wing panels, under the hood. The car number is preceded by three letters and one figure: a) The letter G standing for MG b) The letter H for the Leyland type of engine c) Either N for two-seater Tourer or D for the GT Coupe d) A type serial number, eg 3, 4 or 5 Thus in 1972 the Tourer was GHN5, and the GT GHD5. The car commission number will probably be found on the hood lock platform. The engine number is stamped on a plate secured to the right side of the engine block, or alternatively may be stamped directly upon the block. The engine number starts with the figures 18. This signifies the 1798 cc engine. This used to be lollowed by the letter G lor MG and a second letter lor the type serial. Thus the 18GB followed the 18GA when five main bearings were introduced. This series went through to 18GH. This group of the number had after it a second group giving the type of gearbox: a) U for standard b) RU for overdrive c) We-All synchromesh box d) RWe-AII synchromesh with overdrive e) Rc-Automatic gearbox The engine number/first group is now always 18V and the second group a three figure and one letter serial. Thus in October 1972 the home market was 18V/582F, Europe 18V/581Y and North America 18V/672Z. The engine prefix is followed by one letter, H for high compression ratio and L for low, and then the serial number. The gearbox numberis stamped on the casing of the unit, as is the rear axle number.

Tools and working facilities Introduction A selection of good tools is a fundamental requirement for anyone contemplating the maintenance and repair of a motor vehicle. For the owner who does not possess any, their purchase will prove a considerable expense, offsettmg some of the savings made by doing-it-yourself. However, provided that the tools purchased meet the relevant national safety standards and are of good quality, they will last for many years and prove,an extremely worthwhile investment. To help the average owner to decide which tools are needed to carry out the various tasks detailed in this manual, we have compiled three lists of tools under the following headings: Maintenance and minor repair, Repair and overhaul, and Special. The newcomer to practical mechanics should start off with the Maintenance and minor repair tool kit and confine himself to the simpler jobs around the vehicle. Then, as his confidence and experience grow, he can under- take more difficult tasks, buying extra tools as, and when, they are needed. In this way, a Maintenance and minor repair tool kit can be built-up into a Repair and overhaul tool kit over a considerable period of time without any major cash outlays. The experienced do-it- yourselfer will have a tool kit good enough for most repair and overhaul procedures and will add tools from the Special category when he feels the expense is justified by the amount of use these tools will be put to. It is obviously not possible to cover the subject of tools fully here. For those who wish to learn more about tools and their use there is a book entitled How to Choose and Use Car Tools available from the publishers of this manual. Maintenance and minor repair tool kit The tools given in this list should be considered as a minimum requirement if routine maintenance, servicing and minor repair oper- ations are to be undertaken. We recommend the purchase of combina- tion spanners Iring one end, open-ended the other); although more expensive than open-ended ones, they do give the advantages of both types of spanner. Note that Imperial, metric or a mixture of thread types may be encountered, depending on production date. Combination spanners - t.;\. t .~. t.;\. t. M 7, 8. 9, 10. 11. 12, 13, 17, 19 mm Adjustable spanner - 9 inch Engine sump/gearbox/rear axle drain plug key Spark plug spanner (with rubber insert) Spark plug gap adjustment tool Set of feeler gauges Brake adjuster spanner Brake bleed nipple spanner Screwdriver - 4 in long x t in dia (flat blade) Screwdriver - 4 in long x t in dia (cross blade) Combination pliers - 6 inch Hacksaw (junior) Tyre pump Tyre pressure gauge Grease gun Oil can Fine emery cloth (1 sheet) Wire brush (small) Funnel (medium size) Repair and overhaul tool kit These tools are virtually essential for anyone undertaking any major repairs to a motor vehicle, and are additional to those given in the Maintenance and minor repair list. Included in this list is a comprehensive set of sockets. Although these are expensive they will be found invaluable as they are so versatile - particularly if various drives are included in the set. We recommend the t in square-drive type, as this can be used with most proprietary torque spanners. If you cannot afford a socket set. even bought piecemeal, then inexpensive tubular box wrenches are a useful alternative. The tools in this list will occasionally need to be supplemented by tools from the Special list. Sockets (or box spanners) to cover range in previous list Reversibl€ ratchet drive (for use with sockets) Extension piece, 10 inch (for use with sockets) Universal joint (for use with sockets) Torque wrench (for use with sockets) Mole wrench - 8 inch Ball pein hammer Soft-faced hammer, plastic or rubber Screwdriver - 6 in long x ;\ in dia (flat blade) Screwdriver - 2 in long x ;\ in square (flat blade) Screwdriver - 1 t in long x t in dia (cross blade) Screwdriver - 3 in long x t in dia (electricians) Pliers - electricians side cutters Pliers - needle nosed Pliers - circlip (internal and external) Cold chisel - t inch Scriber Scraper Centre punch Pin punch Hacksaw Valve grinding tool Steel rule/straight-edge Allen keys Selection of files Wire brush (large) Axle-stands Jack (strong scissor or hydraulic type) Special tools The tools in this list are those which are not used regularly, are expensive to buy, or which need to be used in accordance with their manufacturers' instructions. Unless relatively difficult mechanical jobs are undertaken frequently, it will not be economic to buy many of these tools. Where this is the case, you could consider clubbing together with friends lor joining a motorists' club) to make a joint purchase, or borrowing the tools against a deposit from a local garage or tool hire specialist. The following list contains only those tools and instruments freely available to the public, and not those special tools produced by the vehicle manufactu'rer specifically for its dealer network. You will find occasional references to these manufacturers' special tools in the text of this manual. Generally, an alternative method of doing the job without the vehicle manufacturers' special tool is given. However, sometimes, there is no alternative to using them. Where this is the case and the relevant tool cannot be bought or borrowed you will have to entrust the work to a franchised garage. Valve spring compressor Piston ring compressor Balljoint separator Universal hub/bearing puller Impact screwdriver Micrometer and/or vernier gauge Dial gauge Stroboscopic timing light Dwell angle meter/tachometer Universal electrical multi-meter Cylinder compression gauge Lifting tackle Trolley jack Light with extension lead