21 Sep `76
CCE-IHC 20 Ton Dump Truck Exhaust System Leakage Tolerance.
1. Complaints have been received from Army, field user units regarding exhaust system leakage of the CCE-IHC
Paystar F5070 Dump Truck. Being a commercial heavy truck, the exhaust system was required to be in conformance
with the Department of Transportation's Federal Motor Carrier Safety Regulations (49 CFR 393.83). The CCE Dump
Truck met these requirements for the first production model and subsequent production dump trucks should also be in
2. Field tests by safety personnel at one user unit at Fort Meade have made safety checks of exhaust gases in the cab
of the dump trucks that were leaking and determined that the quantity of leakage was below the allowable safety level and
was not considered harmful in the cases tested. Diesel engine exhaust gases are relatively low in carbon monoxide
content and, when the truck is moving, the closed cab is slightly pressurized with fresh air from the (1) front cowl air
3. The commercial criteria for the CCE-IHC dump truck and other heavy trucks is that no exhaust gas leakage be
permitted at exhaust pipe connections forward of the rear of the cab, after a break-in period allowance for those
connections that have been taken apart for maintenance.
4. The maximum carbon monoxide (CO) contamination inside of the cab with a leaking exhaust system is considered to
be when the CO content of 50 parts per million (ppm) is reached. The method of test for CO contamination is
standardized for all vehicles by the Society of Automotive Engineers in the SAE Handbook, SAE 3989 - "Carbon
Monoxide Concentration Test Procedure."
5. Any exhaust system leakage that causes the truck to exceed the legal noise level limits, both in-cab and drive-by,
shall not be permitted.
6. For the commercial heavy truck users, the DOT Bureau of Motor Carrier (BMC) safety inspectors "write-up" the in-
service trucks of these users for any exhaust plumbing leakage that occurs below and forward of the rear outside wall of
the truck cab. The BMC inspectors recognize that flexible section joints will initially leak when first put in service, however
after break-in, the diesel engine's carbon black will soon plug up pin-hole type leaks. The fact that carbon black is present
means that the connection has been leaking in the past. BMC inspectors are instructed to see the leak point and to feel
the exhaust gases with the engine running prior to declaring the vehicle "out-of-service" (deadlined) for under cab
leakage. Exhaust gas leakage rearward of the cab is "written up, " but should not deadline the truck.