Bsi bs au 257 2002

BRITISH STANDARD AUTOMOBILE SERIES

BS AU
257:2002

Code of practice for
remanufacture of spark
and compression
ignition engines

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IC S 43 . 0 6 0 . 0 1

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BS AU 257:2002

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Committees responsible for this
British Standard
The p re parat ion of this British Standard w as e ntrust ed t o Te chnic al
C o m mitte e MC E /2 2 , E ngine s fo r ro ad vehic le s, up on whic h the fo llow ing bo dies
w ere re prese nted:

AE A Te chnolo gy
Auto m ob ile Ass ociatio n
D epartment o f Transp ort
Freight Trans po rt Ass o ciatio n
Garage E quipme nt Asso ciation
Institute o f Ro ad Trans po rt E ngine ers
Mot or Industry Re se arch Ass o ciatio n
Ro ad Haulage Asso ciat ion Ltd.
So c ie ty of Mot or M anufact ure rs and Traders Ltd.
C o op ted mem b ers

This B rit is h St anda rd, ha ving
be e n pr ep are d unde r th e
direct ion o f the E nginee ring
S ecto r Policy a nd S tra te gy
C om m itte e, wa s p ub lis he d
un de r the a utho rity o f the
S tan dards Polic y and S trate gy
Co m m itte e o n 2 O cto be r 2 002

©

BS I 2 O cto b e r 2 002

First p ub lis he d D ece m b e r 1 99 5
S eco nd e ditio n O cto b e r 2 0 02

Amendments issued since publication
Amd. No .

D ate

C o m me nt s

The fo llo wing BS I re fere nces
re la te to the wo rk o n th is
B ritish S tan da rd :
Co m m itte e re fe ren ce MC E /2 2
D r aft fo r co m m ent 9 4/70 877 6 D C

ISBN 0 580 40438 2

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BS AU 257:2002
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Contents
Committees responsible
Foreword
1
2
3
4
5

6
7
8
9
10
11
12
13
14
15

Scope
Definitions
General
Cylinder blocks
Cylinder heads
Crankshafts
Camshafts
Connecting rods
Oil pumps
Water pumps
Ancillary equipment
Assembly
Testing procedures
Documentation
Presentation and protection

1
1
1

2
2
3
3
3
3
4
4
4
4
5
5

i

â BSI 2 October 2002

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Page
Inside front cover
ii

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B S AU 25 7: 20 02

Fore wo rd

This British S tandard has b ee n prep are d by Tec hnical C o mm itte e MC E /2 2. It is
a ne w e ditio n of BS AU 25 7 : 1 99 5 which is w ithdrawn.
As a co de of p ractice, this British S tandard take s the form of guidance and
re co mme ndatio ns. It s hould not b e quote d as if it we re a s pe cificatio n and
particular care should b e t ake n to e ns ure that claims of co mpliance are not
m is leading.

This p ublic ation do es not p urp ort to inc lude all the nec es sary provisions of a
co ntrac t. Us ers are re spo nsib le fo r its c orrec t app licatio n.

C o mp liance w i th a B ri tish S tandar d does not of its elf confer i mmu nity
fro m legal o b ligati on s.

S ummar y of p ages
This doc ume nt co mp rises a fro nt co ver, an ins ide fro nt co ver, pages i and ii,
p age s 1 t o 5 and a back c ove r.

The BS I c opyright no tice dis played in this docume nt indicate s whe n the
document w as last iss ue d.

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BS I 2 O c to b e r 2 0 02


BS AU 25 7: 2 0 0 2

1 S co pe

This Britis h Standard gives recommendations for the techniques to be followed and tasks to be completed
in the remanufacture of a spark or compression ignition engine or of a maj or assembly.

2 D efini tio ns

For the purposes of this British Standard the following definitions apply.
2 .1
re manu factu red engine o r maj o r ass emb ly

used engine or maj or assembly that has been returned to a near- new state in accordance with the

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manufacturer s original specification, with fits and clearances to provide similar performance, reliability
and longevity comparable to that of a new engine
NO TE 1
NO TE 2

“remanufactured” is synonymous with “reconditioned”.
An “exchange ” , “factory” , “reb uilt ” , “repaired ” or “replacement ” engine or assemb ly is unlikely to have b een sub j ected to

For the purposes of this British Standard,

remachining, maj or replacement of parts or restoration of all fits and clearances and is therefore not to be confused with a
remanufactured engine.
2 .2
re new ed c o mp onent

new item s ourced from the manufacturer or supplier who can demonstrate fitness for purpose
2 . 3 M aj o r ass embli es

2.3 .1
s ho rt e ngine

cylinder block cons isting of the crankshaft, connecting rods, pistons and oil and water gallery blanking
p lugs
2.3 .2
cylinder head

unit consisting of all inlet and exhaust valves , valve seats, valve springs and retainers
2 .4
lo ng engine

unit consisting of a s hort engine (see

2 . 3. 1 ),

cylinder head as sembly (see

2 . 3 . 2 ),

camshaft, cam followers

and/or lifters and push rods (where fitted), a cam and/or valve gear cover, an oil pump, timing gears, a
timing chain, a timing chain tensioner and a cover or timing belt, a belt tensioner and timing wheels. The
cylinder block is closed by an engine oil sump with the exception of engines where the transmiss ion cas e
forms the sump

3 Gene ral

3 .1

All engines or assemblies should be dis mantled, the oil and water gallery, cylinder block and head core

p lugs removed, and components thoroughly cleaned, degreased and decarbonized.
3 .2

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All components should be inspected against manufacturers tolerances and should be machined or

renewed as necessary. It is essential that the following components are renewed entirely: p istons; piston
rings; gudgeon pins and retainers; wet cylinder liners (unless rebored) ; main bearings; big end bearings;
thrust washers where fitted; small end bushes; gaskets; oil seals; core plugs; filters; timing chains or timing
belts. New lock washers should be fitted; if unavailable, an alternative locking device should be fitted. If
damaged, threaded holes should be retapped or fitted with thread inserts, or plugged and redrilled and
tapped. Loose dowels s hould be replaced with oversize dowels. All splines, keys, keyways and fasteners

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should be examined for damage and renewed as necessary.

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BSI 2 October 2 002
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1
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B S AU 25 7: 20 02

4 C ylind e r blocks

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4 .1 The cylinder b lock should b e reb o re d o r res le eve d and ho ne d to the pis to n manufac turer s s p ecification
and dim ens ions , including ap propriate s urface finis h. Th e rec es se s o f cylinde r b lo cks fitted w it h rem ova ble
line rs s hould be exam ine d and t rued, and t he se al are as s ho uld be ex amine d and rem achine d as nec ess ary.

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Ne w line r se als s hould b e fit ted. All dim ens io ns sho uld be re stored t o the manufacturer s to lerances as
ne ces s ary b efo re line rs are fit ted. It is e s sential that crac k te sting and/or p re ss ure tes ting are c onduc ted.

4 .2 The m ain b earing housings sho uld be exam ine d fo r siz e, m is alignm e nt and damage , and s hould b e
re m achine d as nece ssary to ensure c orre ct fit o f the ne w b e arings. The lo catio ns o f t hrus t b earings s hould
b e c hec ked and, if out o f to le rance, re claim ed and/or m achine d as nec ess ary.

4 .3 Where the camshaft runs direc tly in the cylinde r b lo ck, the c ams haft b earings s ho uld b e meas ured fo r

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o valit y, alignme nt and tape r to ens ure c learanc es are to the m anufacture r s sp ec ificatio n. Suitable ne w
o ve rs iz e or unders iz e b earings may b e fitte d w here available. Whe re c am fo llo we rs run direc tly in the
cylinde r b lo ck, the cam fo llo we r ho us ing sho uld b e e xamined fo r damage and meas ured for w ear to ens ure

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clearanc es are to the manufacturer s s pe c ificat io n.

4 .4 The top face o f the cylinder b lo ck t op sho uld b e m e asured for flat ness and exam ine d fo r damage and, if

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re quire d, surface - gro und o r m illed to a s urfac e finish co nfo rming to the e ngine o r gas ket m anufac ture r s

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s pe c ifications . Particular at tention sho uld be give n to maintaining de ck heights within the m anufacture r s
s pe c ificatio ns.

4 .5 All o il and wate r galleries sho uld be tho ro ughly cle aned prio r to as s emb ly.

5 C ylin de r he ads

5 .1 The c ylinder bloc k to he ad face s hould b e cleaned and meas ured t o e nsure flatne ss, and s hould b e
mac hine d as ne ces sary t o e nsure flatne s s and that c o rrosion is e liminate d from w at er p orts within the

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gaske t sealing are a. T he c ylinder he ad th ickne ss should b e m aintaine d w ithin the manufacture r s o r

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rem anufac ture r s s pec ific ation. The surface finis h sho uld be as sp e cifie d b y the e ngine o r gaske t
manufact urer. It is ess ential t hat crac k tes ting an d/o r press ure t es ting are conducte d. The roc ke r
co ver/cam ho using j o int face should b e measure d fo r disto rtion and exam ine d for dam age, and sho uld b e
mac hine d as re quire d.

5 .2 Where c ams haft s run direc tly in the c ylinder he ad, b earings s ho uld b e measure d fo r ovality, tape r and

’

alignm e nt to e nsure c le arance s are t o the m anufacturer s spe cific atio n. Whe re t he cam follo we rs run
dire ctly in the cylinder he ad, t he cam fo llow e r housing sho uld be e xam ine d fo r dam age and m easured fo r

’

we ar to ensure cle arance s are to the manufacturer s spe cificat ion.

5 .3 Valve guide s s ho uld b e me as ure d fo r we ar and, if ne ces sary, res ized, res lee ved o r rene we d to c onfo rm

’

to the m anufac ture r s s pec ific atio n.

’

5 .4 Valve springs should be m eas ured agains t the manufacturer s to le rances for squarene ss , fre e length
and co mpre s se d lo ad le ngth and sho uld b e re new ed as ne ce ss ary.

5 .5 Valve colle ts sho uld b e e xamined fo r wear and dam age and s hould b e rene we d as ne ces sary.

5 .6 Valve s s ho uld b e exam ine d fo r dama ge, m easured for straightnes s, head thick nes s and stem w ear, and
re face d or re newe d as ne ce ss ary.

5 .7 Valve seats sho uld be re mac hined and ins e rts re new ed as ne ce ss ary. The valve s eat he ight sho uld

’

c onfo rm to t he manufac turer s spe cification.

5 .8 All valve o pe rating asse mblie s s hould b e c om ple te ly dism antle d, clea ne d and e xamine d fo r we ar and
o ther defe cts . C om po nents sho uld be m ac hined or re ne w ed as nec ess ary. Pus h ro ds s hould b e ex amine d fo r
straightnes s, damage and we ar, and sho uld be re new ed as nece ss ary. It is e sse ntial that t he valve t rain
geo m e try is maintaine d o n the c om p one nt as sem b ly.

5 .9 All o il and wate r galleries sho uld be tho ro ughly cle aned prio r to as s emb ly.

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BS I 2 O cto b e r 2 00 2


BS AU 25 7: 2 0 0 2

6 C ranksh afts

6 .1 The o il gallery plugs sho uld be re m ove d as ne ce s sary and the c ranks haft sho uld b e e xam ined for
damage. D ies el engine crankshafts s hould b e crack te ste d afte r any mac hining p ro ce ss and prio r to
ass e mb ly.

6 .2 S ealing diame ters and no s e ends sho uld b e m eas ured and, if ne ces s ary, re claim ed. Jo urnal w ear,
b le nde d radii, thrust we ar and a lignm ent should be meas ure d. C e rtain c rankshafts m ay b e st raighte ned,
depe nding upo n t he m ate rial, b ut it is e sse ntial tha t this o pe ration is fo llowe d b y furthe r crack dete ct ion.

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6 .3 C ranks hafts s hould b e re gro und o r po lishe d to co nform t o the be aring m anufac ture r s dimensional,
s urfac e finis h and ha rdne s s spe cificatio n. O ne or m o re crankshaft j ournals and seal are as may be
re claimed b y rec ognize d welding o r m e tal sp raying t ec hniques and then regro und to maintain parity with

’

the o the r j ournals . It is e ss ential that cranks haft hardne ss is m aintaine d to the manufac ture r s
s p ec ifica tio n.

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6 .4 Afte r grinding, all crankshafts should b e p olis hed to c onform to the b e aring m anufact urer s
s p ec ification fo r surfac e finis h.

6 .5 All oil holes s hould b e de b urre d and oil galleries thoroughly c le ane d prior to ass e mb ly.

7 C amsh afts

7 .1 C ams hafts s hould b e e xamine d for dam age and m e as ure d for s traightne ss and we ar on j o urnals, lo be s
and ske w gea r. If nece ssary the cam lo b es should b e rep ro file d o r the c amshaft rene we d.

7 .2 C am fo llow ers s hould b e re face d or re new ed as nec es sary. All hydraulic valve o pe rating c om po ne nts
sho uld b e rene we d if uns ervice able afte r a full s trip and inspe ction.

8 C o nne cti ng ro ds

8 .1 B ig e nd b earing ho usings sho uld b e m easure d for s iz e and o valit y and sho uld b e re s iz e d as ne ce s sary.
S ide face s s ho uld b e e xamine d, and b e aring kee p s a nd oilw ays de burred and tho roughly cle ane d p rior to
ass e mb ly.
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8 .2 C o nne c ting ro ds sho uld be m easure d fo r alignme nt and straight ened as nece ss ary.

8 .3 Small e nd b ushes sho uld be re new ed and re m achine d to give t he gudge on p in to b us h c le aranc e
sp ecifie d b y the manufac ture r, afte r e nsuring that the ho us ing is w it hin dim ens io nal lim its . The

’

int erferenc e fit of p re s s- fit gudgeo n p ins to sm all e nd b ores s ho uld be maintaine d to the manufact ure r s
sp ec ifica tio n.

8 .4 Big e nd studs and b olts sho uld b e e xam ined and any s ho wing signs of stretc h or damage s ho uld b e
re new e d.

8 .5 C o nne c ting ro ds sho uld be m atc hed as a we ighte d s et.

9 O il pumps
O il pum ps should b e e xamined for internal s co ring and da mage and me as ured fo r roto r to b ody c le arance
as de fine d b y the ma nufacturer. T he pres sure relief valve as se m bly should be dismantled and c le ane d. All
no n- c onfo rming p arts sho uld b e rene wed.

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BS I 2 O cto b e r 2 00 2
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3

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B S AU 25 7: 20 02

1 0 Wate r pump s

If fitted b y the remanufacturer, water p umps s hould b e remanufactured to the original equip ment
specification or renewed.

1 1 Anci llary e qui pme nt

1 1.1

All tooth belts and timing chains should b e renewed. Chain wheels and gears should be examined for
óóÀơ ơ ÀóÀóÀơ ơ Àơ ơ Àơ Àơ ơ Àóóó

wear or damage and renewed as necess ary.
1 1.2

Worn tim ing chain guides and chain tensioners should b e renewed.

1 1.3

Toothed belt s prockets should b e examined for wear or damage and renewed as required.

1 1.4

Where fitted, crankshaft torsional vibration damp ers and/or crankshaft p ulleys should be examined

for wear or dama ge and renewed as required.
1 1.5

Any other comp onents, the condition of which may influence engine performance or durab ility, should

b e s trip ped, examined and remanufactured or renewed as necessary.
1 1.6

All fasteners and threads should b e examined and renewed as necessary.

1 2 Ass e mb ly

1 2. 1

All comp onents should be thoroughly cleaned b efore assemb ly. E ngine reassemb ly should b e carried

’

out strictly in accordance with the manufacturer s guidelines, with p articular attention being paid to b olt
tightening sequences and torque procedures.
1 2. 2

It is ess ential that measurements include piston heights, va lve- p ocket dep ths, pis ton- skirt clearance,

valve timing, tapp et clearances, and crankshaft end floa t and bearing clearances. It is essential that tests
are carried ou t during assembly to ensure that each valve and its s eat forms an efficient seal. It is essential
that breathing comp onents forming p art of the engine are neither contaminated nor damaged.
1 2. 3

The remanufactured engine or maj or ass emb ly should be perma nently identified b y a unique s erial

number. This serial numb er should b e reproduced on the warranty document.

1 3 T es tin g pro ce dure s

A minimum test for a long engine should be cap able of indicating or detecting the following:
a) oil p ressure;
b ) comp ression;
c) oil leaks .
Items a) and b ) should b e recorded.

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BS I 2 O ctober 2 00 2


BS AU 25 7: 2 0 0 2

1 4 Do cume ntatio n

1 4. 1

Each remanufactured engine or maj or ass emb ly should have its own b uild document containing

records of:
a) components renewed;
b ) serial numb er;
c) comp letion date;
d) tes t records.
This document shou ld b e retained b y the remanufacturer and made availab le to the customer in the event
of a disp ute.
1 4. 2

An information p ack detailing the following s hould b e attached to the remanufactured engine or maj or

assemb ly:
a) serial numb ers;
b ) fitting instructions;
c) running- in p rocedures;
d) written warranty.

1 5 Pre s e ntatio n an d p rotection

The completed remanufactured engine or maj or assembly should b e p ainted and suitably p rotected against
ingress of dirt, corrosion and physical damage.

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íĐđÃạáơ ịđÃơÃ-á ơẳđẳ- ì-ơÃơôơÃ
BS I 2 O cto ber 2 00 2
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úúụ ụ úúụ ụ ụ ụ ụ ụ ụ úúú

5
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BS AU
257:2002

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details are to be used for any other purpose than implementation then the prior
written permission of BSI must be obtained.
Details and advice can be obtained from the Copyright & Licensing Manager.
Tel: +44 (0)20 8996 7070. Fax: +44 (0)20 8996 7553.
Email:

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