09-1

Air Cleaner Modifications for Dusty Environments

Thomas Built Buses
Service Bulletin

> Saf-T-Liner C2

General Information
Inspecting the air intake system for damage or leaks should be performed daily as outlined in the Daily Pretrip
Inspection and Maintenance Procedures of the Saf-T-Liner C2 School Bus Driver’s Manual.
Ensuring that the air cleaner element maintenance is performed at the scheduled intervals for vehicles operating
in dusty environments is very important. See section 00-05 in the Saf-T-Liner C2 School Bus Maintenance
Manual to determine the correct schedule for your vehicle.
This bulletin provides information for air cleaner element inspection and replacement, as well as, air intake seal
installation and leak check.

Air Cleaner Element Inspection and Replacement
IMPORTANT: Due to the variety of possible driving conditions (dirt roads, paved roads, etc.), it is
critical to check the air restriction indicator, if so equipped. If the vehicle is not equipped with an air
restriction indicator, inspect all components of the air intake system and air filter every six months.
Replace the air filter every 12 months, or when filter restriction reaches 25 inH2O for diesel engines,
or when the air restriction indicator is completely red for propane engines (if equipped with an air
restriction indicator). More frequent inspections and/or filter replacement may be needed if the
vehicle is being operated in a dusty environment, to avoid damaging the engine.

Inspection
Remove and visually inspect the air filter for holes, tears, cracks, or other damage at the recommended interval.
Remove loose debris, such as leaves or pine needles, from the filter housing. If the air filter is damaged,
replace it. See Group 09 of the Saf-T-Liner C2 School Bus Workshop Manual for removal and installation
instructions, or take the vehicle to an authorized Freightliner dealer.
Engine damage can occur if the air intake system is not properly maintained. Use the air intake restriction
indicator to check for air intake system damage or leaks. See Fig. 1 and Fig. 2. Make sure the engine is off
and note the existing reading on the indicator. Reset the indicator by pushing it down. See Fig. 1 and Fig. 2.
Start the engine and take a short test drive. Check the indicator again and note the level of restriction on the
indicator. A decrease from the previous level of restriction or a very low air restriction indicator reading (0 to 4
inH2O) could indicate an air intake system problem such as a damaged air filter, loose or

disconnected air intake piping, or a disconnected or damaged air restriction indicator.

Replacement
NOTICE
Do not use aftermarket air-cleaner elements. Aftermarket air-cleaner elements may not seal the housing
correctly, which can lead to engine damage and potentially the loss of warranty. When replacing an aircleaner element, use only the part listed in PartsPro® for the serial number of the vehicle.
Replace the air filter every 12 months, or when filter restriction reaches 25 inH2O for diesel engines, or when

the air restriction indicator is completely red for propane engines (if equipped with an air restriction
indicator). See Group 09 of the Saf-T-Liner C2 School Bus Workshop Manual for removal and installation

instructions, or take the vehicle to an authorized Freightliner dealer.

Thomas Built Buses Service Bulletin, May 2016

Page 1

09-1

Air Cleaner Modifications for Dusty Environments

Thomas Built Buses
Service Bulletin

> Saf-T-Liner C2

H O VACUUM
2

IN

25
20
15
10
7

H O VACUUM
2

H O VACUUM
2

IN

25
20
15
10
7

H O VACUUM
2

PUSH TO RESET

PUSH TO RESET

A

B
f090165

08/21/96

A. Partial Restriction

B. Full Restriction
Fig. 1, Air Restriction Indicator, Diesel Engines

A

B

12/02/2011

A. Partial Restriction

f090495

B. Full Restriction

Fig. 2, Air Restriction Indicator, Propane Engines

Air Intake Seal Installation and Leak Check
It is recommended that vehicles operating in dusty environments that are equipped with air cleaner 03-37678000, install air intake seal 03-35087-002. This will improve the sealing quality of the air cleaner and help prevent
dust from entering the air intake ducting. See the steps below for seal installation.
1. Park the vehicle on a level surface, shut down the engine, and set the parking brake. Chock the tires.
2. Loosen the clamps at the air cleaner and turbocharger, then remove the air intake duct. See Fig. 3.

Page 2

Thomas Built Buses Service Bulletin, May 2016

09-1

Air Cleaner Modifications for Dusty Environments

Thomas Built Buses
Service Bulletin

> Saf-T-Liner C2

2
3

1

4

5
5

6

f090519d

11/03/2015

1. Air Cleaner Assembly
2. Screw
3. Washer

4. Mounting Bracket
5. Clamp
6. Air Intake Duct

Fig. 3, Air Cleaner Assembly Installation

3. Remove any dust and debris in the air cleaner outlet.
4. Install the air intake seal on the air cleaner outlet as shown in Fig. 4.

NOTE: P-80® Rubber Lubricant Emulsion eases installation of tight-fitting rubber and plastic parts by
reducing the force needed for assembly. Once assembly is complete, the emulsion dries and the part
returns to its original condition. Use P-80 Rubber Lubricant Emulsion when a thin film of lubricant is
desired.
5. Apply P-80 Rubber Lubricant Emulsion to the seal and base of the air cleaner housing to help install the
housing into the duct. See Fig. 5.

Thomas Built Buses Service Bulletin, May 2016

Page 3

09-1

Air Cleaner Modifications for Dusty Environments

Thomas Built Buses
Service Bulletin

> Saf-T-Liner C2

1
2

3

4
1
2

10/13/2015

1. Air Cleaner Assembly

f090521

2. Seal

Fig. 4, Assembly, Air Intake Seal and Housing
10/13/2015

f090520

1. Air Cleaner Housing
2. Seal

3. Air Duct
4. Clamp

Fig. 5, Installation, Air Intake Seal and Housing

6. Wipe clean the inside and outside of the air duct, then install it on the vehicle. Tighten the clamp at the
turbo charger 90 lbf·in (1017 N·cm) and the clamp at the air cleaner 40 lbf·in (452 N·cm).
7. Use the air intake restriction indicator to check for air intake system damage or leaks. See Fig. 1 and Fig.
2. Make sure the engine is off and note the existing reading on the indicator. Reset the indicator by
pushing it down. See Fig. 1 and Fig. 2. Start the engine and take a short test drive. Check the indicator
again and note the level of restriction on the indicator. A decrease from the previous level of restriction or a
very low air restriction indicator reading (0 to 4 inH2O) could indicate an air intake system problem

such as a damaged air filter, loose or disconnected air intake piping, or a disconnected or
damaged air restriction indicator.

Parts
The seal is available through the Parts Distribution Center (PDC). For air cleaner 03-37678-000, use air intake
seal 03-35087-002.

Warranty
This is an informational bulletin only; warranty does not apply.

Page 4

Thomas Built Buses Service Bulletin, May 2016