Step-by-Step Removal Instructions
The thermostat on the 2008 Triumph Rocket III Classic is located in the thermostat housing at the top front of the engine, near the cylinder head. It's a standard wax-pellet type that opens around 82–85°C (180–185°F). Removing it requires draining the coolant first. These steps are based on the official service manual procedures for the Rocket III series (applicable to 2004–2013 models, including the 2008 Classic).
- Prepare the Motorcycle:
- Park on a level surface and let the engine cool completely (at least 2–3 hours after riding).
- Remove the rider's seat for better access (see page 17-17 of the service manual: lift the seat latch under the side cover and pull up).
- Drain the Coolant:
- Place a drain pan under the radiator (right side of the bike).
- Open the radiator drain tap (bottom of the radiator) and remove the radiator cap slowly to relieve pressure.
- Drain all coolant into the pan. Close the drain tap once empty.
- Also loosen the water pump drain plug if needed (tighten to 10 Nm when done).
- Disconnect the Hoses:
- Locate the thermostat housing on the top right of the engine (near the radiator top hose).
- Loosen the hose clamps on the top radiator hose and the bypass hose (connected to the cylinder head).
- Gently twist and pull the hoses off the thermostat housing barbs. Expect some residual coolant—have rags ready.
- If clamps are screw-type, use a screwdriver; if spring-type, use pliers.
- Remove the Thermostat Housing:
- Remove the two bolts securing the thermostat housing to the cylinder head (typically 10mm sockets; torque spec for reinstall is 10–12 Nm).
- Carefully lift off the housing. The thermostat sits inside, sealed with an O-ring or gasket—note its orientation (jiggle valve up).
- Extract the Thermostat:
- The thermostat may pop out with the housing or stick inside the head. If stuck, gently pry it out with a flathead screwdriver—avoid damaging the mating surfaces.
- Inspect the old thermostat: Test it in boiling water (it should open at ~82°C). Clean the housing and head of old gasket material.
Reinstallation (If Replacing)
- Install a new thermostat (OEM part T3050301 or equivalent) with the correct orientation.
- Fit a new O-ring/gasket to the housing.
- Reattach the housing, torque bolts to 10 Nm.
- Reconnect hoses and tighten clamps securely.
- Refill with coolant: Open the bleed screw on the thermostat housing, slowly add coolant to the radiator until full, then top off the expansion tank. Close the bleed screw when coolant flows out steadily (no air bubbles).
- Run the engine to operating temperature, check for leaks, and top off coolant as needed. Bleed air by idling until the fan cycles.