FSB-252-029

Field Service Bulletin
Trucks
SB-10055987-7359
Mack Trucks, Inc.
Greensboro, NC USA
This field service bulletin replaces bulletin 252-029 dated 9.2013.
Date
Group
No.
Release
Page
5.2014
252
029
02
1(7)
Muffler Inlet Pipe
ISL-G
MRU
FSB 252-029, Muffler Inlet Pipe
(May 2014)
Some MACK MRU trucks equipped with the Cummins ISL-G engine built before September
16, 2013 may experience a issue with the muffler inlet pipe falling out of the muffler. A new
muffler inlet pipe, lengthened exhaust flex pipe and a turbocharger outlet pipe has been
design to work together to reduce rigidity of the exhaust to address this condition. The new
exhaust has been implemented in production and is now available in the aftermarket for any
vehicle that may encounter this condition
All three exhaust pipes need to be installed together for correct installation.
Note: The exhaust clamps must NOT be reused, they are one time use only parts. The
correct torques can not be reproduced once loosened.
Part Number
Description
Quantity
22216914
Exhaust Pipe (MRU Muffler
Inlet)
1
22216925
Hose Exhaust (Flex Pipe)
1
22216977
Exhaust Pipe (Turbocharger
Outlet)
1
21380071
Clamp
2
25020944
Clamp (Catalyst Inlet)
1
21465729
Clamp (Turbocharger
Outlet)
1
Note: Transfer parts as needed such as sensor and heat shield.
PV729-FSB252-029
USA64922
Mack Trucks, Inc.
Field Service Bulletin
Date
5.2014
Group
No.
Release
252
029
02
You must read and understand the precautions and guidelines in Service Information,
Function Group 20, "Engine Safety Practices" before performing this procedure. If you are
not properly trained and certified in this procedure, ask your supervisor for training before
you perform it.
Procedure
1 Secure the vehicle for service by parking it on a flat level surface, applying the parking
brake, chocking the rear wheel, and placing the transmission in neutral.
2 Disconnect all cables from the negative (ground) and positive battery terminals to prevent
personal injury from electrical shock and prevent damage to electrical components.
3 Disconnect sensor connector from sensor in turbocharger outlet pipe.
4 Secure any loose items in the cab to prevent damage to the dash or windshield when the
cab is tilted. Unlock the pump and tilt the cab forward.
5 Remove the V-band clamp at the turbocharger outlet pipe and separate pipe from
turbocharger.
6 Mark the clamp bolt location on the exhaust catalyst inlet.
7 Loosen the clamp bolt and disconnect the exhaust pipe from the exhaust catalyst inlet.
Discard the band clamp.
W2070233
8 Remove the exhaust pipe assembly and discard.
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Mack Trucks, Inc.
Field Service Bulletin
Date
5.2014
Group
No.
Release
252
029
02
9 Inspect the exhaust catalyst inlet flange by measuring the inside diameter at three
locations (X, Y and Z). The inside diameter must be 101.7 – 102.7 mm (4 – 4.04 in). If
necessary, gently tap the flange inward or outward to meet the specification.
W2089472
10 Clean the sealing surfaces on the exhaust catalyst inlet.
11 Adjust flex pipe to 300 mm (12 in) in length (B). To determine the clamp insertion depth on
the flex pipe, mark 35 mm (1.5 in) from either end (A).
W2089513
A = 35 mm (1.5 in), B = 300 mm (12 in)
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Mack Trucks, Inc.
Field Service Bulletin
Date
5.2014
Group
No.
Release
252
029
02
12 To determine insertion depth of piping into clamps, mark the turbocharger outlet pipe and
the catalyst inlet pipe 76 mm (3 in) inward from the mating end to the flex pipe.
W2089516
A = 76 mm (3 in)
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Mack Trucks, Inc.
Field Service Bulletin
Date
5.2014
Group
No.
Release
252
029
02
13 To determine insertion depth of the inlet pipe into catalyst inlet flange, mark 58 mm (2.25
in) from end of catalyst inlet pipe.
W2089517
A = 58 mm (2.25 in)
14 Loosen and remove the band clamp/heat shield assembly from the old exhaust catalyst
inlet pipe.
15 Position the heat shield on the new exhaust catalyst inlet pipe.
16 Install the band clamp securing the flex pipe to the exhaust catalyst inlet pipe and tighten
the band clamp to 48 ±7 Nm (35 ±5 lb-ft).
17 Install the band clamp securing the turbocharger outlet pipe to the flex pipe.
Note: Only hand tighten the band clamp at this time to allow the turbocharger outlet pipe to
be rotated into position during the installation of the exhaust pipe assembly. Use the
alignment marks as guides.
18 Install the exhaust pipe assembly into position. Use the alignment mark as a guide.
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Mack Trucks, Inc.
Field Service Bulletin
Date
5.2014
Group
No.
Release
252
029
02
19 Position clamp so that top of all slots are covered by clamp and clamp spacer block is
between slots. Ensure exhaust catalyst inlet flange aligns with previously indicated mark
on inlet pipe. Position and tighten the band clamp at the catalyst inlet to 60 ±7 Nm (45 ±5
lb-ft).
W2089689
20 Install a new V-band clamp at the turbocharger outlet and tighten to 48 ±7 Nm (35 ±5 lb-ft).
21 Tighten the band clamp at the turbocharger outlet pipe to flex pipe to 48 ±7 Nm (35 ±5 lbft). Use the alignment marks as guides.
22 Position the heat shield on the exhaust catalyst inlet pipe and tighten to 9 ±1 Nm (84 ±12
lb-in).
23 Connect sensor connector to sensor in turbocharger outlet pipe.
24 Lower the cab to the closed and locked position.
25 Install all previously removed cables to the negative (ground) battery cables.
26 Start the engine, check for leaks and proper operation. Use Guided Diagnostics to read
and clear any diagnostic trouble codes (DTC).
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Mack Trucks, Inc.
Field Service Bulletin
Date
5.2014
Group
No.
Release
252
029
02
Reimbursement
This repair may be eligible for reimbursement if a product failure was experienced
within time and mileage limits of the applicable Warranty coverage. Reimbursement
is obtained via the normal claim handling process.
Claim Type (used only when uploading from the Dealer Bus. Sys.)
01
Labor Code
Primary Labor Code
2343E-ZU-80
— 0.9 hrs
Causal Part
21533953
MACK Trucks North America engages in a comprehensive 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 vehicles.
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