Cummins/Onan 5.5 NH / 6.5 NH — Mobile Exhaust System Installation
Installation
For the Cummins/Onan 5.5 NH / 6.5 NH, from the Cummins/Onan operator's manual.
Applies to: Cummins/Onan NH engine
Before you start
- Inhalation of exhaust gases might result in severe personal injury or death. Plan the exhaust system carefully to prevent exhaust gases from entering the vehicle interior.
- Do not terminate the exhaust tailpipe under a window or door, ahead of the air intake, under the fuel tank fill spout, or under the vehicle.
Procedure
- Leave adequate clearance where the exhaust passes through the base or floor; turn up the metal or use a collar.
- Keep the exhaust system no closer than 1-1/2 inches from any combustible material, or insulate/shield it.
- Secure the exhaust downpipe to the exhaust manifold using 5/16-18 bolts, lock washers, and nuts, with a new asbestos gasket.
- Attach the muffler inlet to the downpipe using a 1-5/8 inch automotive type U-bolt clamp only.
- Use 1-3/8 inch ID, 18 gauge rigid steel tubing for tailpipe; do not use flexible exhaust tailpipe.
- Use 1-1/2 inch U-bolt type automotive muffler clamps and shock mounted hangers.
- Extend the tailpipe at least one inch (25 mm) beyond the perimeter of the vehicle, directing gases down and away.
- Do not connect the generator set exhaust tailpipe to the vehicle exhaust system.
- Attach the tailpipe to the outlet end of the muffler and support with a shock mounted support hanger with clamp.
- Run the generator set for five minutes and check the entire exhaust system visually and audibly for leaks or excessive noise.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Exhaust at least 1-1/2 inches from combustible material or fuel tank
- Exhaust heat must not raise temperature of combustible material more than 117°F (65°C)
- Tailpipe: 1-3/8 inch ID, 18 gauge rigid steel tubing
- Tailpipe extension: at least 1 inch (25 mm) beyond vehicle perimeter
Source: Cummins/Onan operator's 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.