IK0400016

IK0400016 - Aggressive Brakes with Air Brake Foot Valve Leak on Bus
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TOBAGO, UNITED STATES,
IK0400016
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Availability: ISIS, Bus ISIS, FleetISIS, IsSIR
Revision: 5
Major
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BRAKES
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11/5/2018
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5/10/2007
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Title : Aggressive Brakes with Air Brake Foot Valve Leak on Bus
Applies To : CE200, CE300, FE300, RE200 and RE300 with Option Code 04WEA - Parking
Brake Interlock - With Air Brakes Only
CHANGE LOG
Please refer to the change log text box below for recent changes to this article:
11/05/2018 - Updated Symptoms and diagnostic information


DESCRIPTION
Vehicles equipped with Feature code 04WEA Park Brake Interlock require the key to be on and the brake pedal to be depressed to
release the parking brake. To accomplish this there is additional (see Figure 1) air line routing and valving added to the base system
(See Figure 2). When the brake is applied air is routed from the foot valve through a double check valve to an ignition controlled
solenoid valve through another double check valve and to the control inputs on an SV-1 valve for the primary and the secondary air
systems. The control air in the SV-1 valve opens the supply port to the delivery port and sends air to the park brake valve. Once the
park brake is released there is air feed through the second double check valve to the SV-1 to provide air to hold the park brake in the
released position.
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Figure 1: Feature Code 04WEA add on Air Schematic
Yellow = Park brake circuits
Green = Primary air circuits
Orange = Secondary air circuit
Black = 04WEA control circuit
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Figure 2: Base Truck and Bus Air Schematic
SYMPTOM(s)
An air leak at the foot valve can be cause by a leaking double check valve in the 04WEA control circuit. This will back-feed air into the
delivery port on the foot valve and will be exhausted out the exhaust port on the foot valve at key on with the parking brake released
and the brake pedal not depressed.
It is also possible for back-feeding air to cause the brakes to become touchy or grabby during a light brake application. This is due
to the fact that the exhaust port on the foot valve is closed off once the brake pedal is applied and the back-feeding air now is trapped
between the foot valve and the brake chambers. There is also the normal application air being added to the delivery circuit based on
the amount of travel on the brake pedal. The back-feeding air and the normal application air has a compounding effect and creates a
greater than desired braking force.
Note: At times it is possible to get the double check valve to seat by having a full service brake application.
SERVICE PARTS INFORMATION
Kit Description
Part Number
Quantity
Required
Double Check Valve
3604589C1
1
Notes
WARNING:
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To prevent unexpected movement of the vehicle and possible serious personal injury or death, park the vehicle on a flat,
level surface, set the parking brake, turn the engine off and chock the wheels to prevent vehicle from moving in both
directions.
WARNING:
To prevent serious eye injury, always wear safe eye protection when you perform vehicle maintenance or service.
Step Action
DIAGNOSTIC: Verify leak at foot valve.
Decision
Yes: Proceed to step 2.
Attempt to verify the air leak is present at the foot valve with the Key
on and the parking brake release. It may take multiple time setting
and releasing the parking brake before a leak will be present.
1
No: End of diagnostics.
Were any leaks found (see figure 3)?
Step Action
2
DIAGNOSTIC: Key Off air leak
With the air leak at the foot valve, turn the key to the off position and
leave the parking brake released.
Decision
Yes: Replace the double check
valve.
No: Diagnose other source of backfeeding air.
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Does the air leak move to the ignition controlled solenoid (see
figure 4)?
Figure 3: Air leak from the foot valve
Highlighted yellow shows path of back-feeding air.
Air leaks from the foot valve at key on, parking brake released, service brakes not applied.
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Figure 4: Key off leak location
Highlighted yellow shows path of back-feeding air.
Air leaks from the ignition controlled solenoid at key off with park brake released.
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Figure 5: Leak Locations
Figure 6: Double Check Valve and SV-1 Valves
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WARRANTY INFORMATION
Warranty Claim Coding:
Refer to the Warranty Coding Manual for Group and Noun Codes.
Standard Repair Time(s):
Refer to the SRT Manual for Repair Times
OTHER RESOURCES
Master Service Information Site
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