SB-10044959-9167

Field Serv ic e B ulletin
Tr u c k s

M a c k Tr u c k s , I n c .
Greensboro, NC USA

Date

Group

No.

Release

Page

7.2012

258

033

01

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Engine Turbocharger Compressor Bypass
Valve, Air Line Routing
CXU, GU
MP7

F S B 2 5 8 - 0 3 3 , E n g i n e Tu r b o c h a r g e r C o m p r e s s o r
B y p a s s Va l v e , A i r L i n e R o u t i n g
(J uly 2012)
The existing steel engine turbocharger compressor bypass valve air line has been replaced
by a flexible braided plastic line on MACK CXU and GU trucks equipped with MP7 engines
that still have the engine turbocharger compressor bypass valve in use. This document
covers the procedure for routing the flexible air line around the front of the engine if the
existing steel air line fail.
N o t e : This bulletin does not apply to MACK Trucks Australia.

W2074483

R eq ui red P a rt s
E n g i n e Tu r b o c h a r g e r C o mp r e s s o r B y p a s s Va l v e , A i r L i n e P a r t s a n d Ma r k i n g s
Item #

Part Number

QTY

1

21485498

1

Pipe Set Air Line

2

20885496

6

Retainer

3

883699

3

Retainer Clip

4

N/A

N/A

PV729-FSB258-033_M

De sc ription

Alignment Mark

USA54180

M a c k Tr u c k s , I n c .
Field Service Bulletin

Date
7.2012

Group

No.

Release

258

033

01

P roc edu re
You must read and understand the precautions and guidelines in Service Information,
group 20, "General Safety Practices, Engine" before performing this procedure. If you are
not properly trained and certified in this procedure, ask your supervisor for training before
you perform it.
1 Apply parking brake and place shift lever in neutral.
2 Using wheel chocks, secure truck on a flat and level surface.
3 Unlatch and raise hood.
4 Disconnect all battery cables from the negative (ground) battery terminals to prevent
personal injury from electrical shock and prevent damage to electrical components.
5 Remove left inner fender and bracket.
6 Remove the passenger seat.
7 Remove lower dash trim panels.
8 Remove engine cover.
9 Cut the existing air line into two sections at the rear of cylinder head.

W2074484

10 Remove all p-clamps and cable ties securing the air line at the rear and hot side of the
engine.

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M a c k Tr u c k s , I n c .
Field Service Bulletin

Date
7.2012

Group

No.

Release

258

033

01

11 Disconnect the air line and remove it from the engine turbocharger compressor bypass
valve to the rear of the engine.

W2074485

12 Disconnect the air line from the control valve.

W2074486

13 Cut cable ties as needed, then remove line on the hot side of the engine.

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M a c k Tr u c k s , I n c .
Field Service Bulletin

Date
7.2012

Group

No.

Release

258

033

01

14 Starting at the front of the engine, align the white mark on the new engine turbocharger
compressor bypass valve air line as shown in the figure below. Route the new air line
above exhaust gas recirculation (EGR) pipe and behind the alternator as shown in the
figure below.

W2074487

15 Feed air line behind the alternator and alongside the fuel line.
N o t e : Note orientation of line fittings to ensure proper alignment for connection.
16 Continue routing the air line along the fuel line and under the bracket. Connect fitting to the
control valve as shown in figure below.
N o t e : Temporarily snug fitting, but do not tighten.

W2074488

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M a c k Tr u c k s , I n c .
Field Service Bulletin

Date
7.2012

Group

No.

Release

258

033

01

17 Route remaining engine turbocharger compressor bypass valve air line behind the radiator
fan bracket and parallel to the wiring harness.

W2074489

18 Connect fitting to engine turbocharger compressor bypass valve.
N o t e : Temporarily snug fitting, but do not tighten.

W2074490

19 Verify position of air line and tighten all fittings to 17 ± 1Nm (150 ± 9 in-lb).

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M a c k Tr u c k s , I n c .
Field Service Bulletin

Date
7.2012

Group

No.

Release

258

033

01

20 Using supplied retainer clips and retainers, secure new air line as shown in figures below.

W2074491

W2074492

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M a c k Tr u c k s , I n c .
Field Service Bulletin

Date
7.2012

Group

No.

Release

258

033

01

W2074493

21 Build air pressure to operating pressure.
22 Check the engine turbocharger compressor bypass valve air line and connections for
leaks by activating the actuator in Vehicle Computer Aided Diagnostic System (VCADS)
function 2545–08–03–02.
23 Install engine cover.
24 Install lower dash trim panels.
25 Install passenger seat.
26 Install left inner fender and bracket.
27 Reconnect all previously removed cable to the negative (ground) battery terminals.
28 Close hood and latch hood.
29 Remove wheel chocks.

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M a c k Tr u c k s , I n c .
Field Service Bulletin

Date
7.2012

Group

No.

Release

258

033

01

R ei mbu rs ement
Thi s repai r may be el igi bl e for rei mbu rs ement i f a produ c t fa il ure w as e x pe rien c ed
w i t h i n t i m e a n d m i l e a g e l i m i t s o f t h e a p p l i c a b l e Wa r r a n t y c o v e r a g e . R e i m b u r s e m e n t
is obta ine d v i a the no rmal c l aim handl i ng proc es s .
C l a i m Ty p e ( u s e d o n l y w h e n u p l o a d i n g f r o m t h e D e a l e r B u s . S y s . )

W

Labor Code
Primary Labor Code

2141T-26-80
2.5 hrs.

Caus al P art

21365802

MACK Trucks North America engages in a continuous program of testing and evaluating to
provide the best possible product. MACK Trucks North America, however, is not committed
to, or liable for updating existing chassis.

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