Cummins/Onan — Exhaust Tailpipe Connection and Routing
Installation
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan HDKA, Cummins/Onan HDKAL/HDKAS engine
Before you start
- EXHAUST GAS IS DEADLY! Do not terminate the exhaust tailpipe underneath the vehicle or closer than specified to openings into the vehicle.
- Tailpipes are hot and can cause severe burns.
Procedure
- Use 18-gauge aluminized steel tubing; for lengths up to 20 feet (6 m) use 1-1/2 inch ID or larger tubing.
- Use U-bolt muffler clamps to connect tailpipe sections; slot the overlapping pipe.
- Use automotive-type tailpipe hangers every 2 to 3 feet (0.6 to 0.9 m), attached to steel framework.
- Do not terminate the tailpipe underneath the vehicle; extend at least 1 inch (25 mm) beyond the vehicle perimeter.
- Do not route the tailpipe where it will interfere with draining engine oil or coolant.
- Do not route the tailpipe closer than 3 inches (76 mm) to combustible material unless insulated or shielded.
- Guard the tailpipe against accidental contact unless it is routed underneath the vehicle.
- Do not route the tailpipe near fuel lines or fuel tanks.
- Do not terminate the tailpipe closer than 6 inches (153 mm) to any opening into the vehicle interior.
- Do not connect the genset to the vehicle engine exhaust system.
- Route the tailpipe out of the approach and departure angles and above the axle clearance line.
- Keep exhaust back pressure under full load below 1.57 inches (40 mm) mercury column.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 18-gauge aluminized steel tubing
- 1-1/2 inch ID minimum up to 20 feet (6 m)
- 1 inch (25 mm) minimum beyond vehicle perimeter
- 3 inches (76 mm) minimum to combustible material
- 6 inches (153 mm) minimum to openings
- 1.57 inches (40 mm) mercury column maximum back pressure
Full service-parts list: Cummins/Onan HDKA →
Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.