Parts for your 2006 Toyota Bb-Thermostat

2006 Toyota bB Thermostat — What it does and when to replace it

A thermostat is absolutely used on the 2006 Toyota bB. Technical references that cover this include the Toyota Electronic Parts Catalog (EPC) for the QNC20/QNC21 chassis and the Toyota bB Repair Manual (Cooling section), both of which show a wax‑pellet thermostat in the cooling system. The engines fitted to this model (1.3 K3‑VE and 1.5 3SZ‑VE, shared with Daihatsu) also specify an approximately 82°C opening thermostat in their factory engine manuals. It’s mounted at the water inlet housing on the engine block, with an O‑ring or gasket seal.

On the 2006 bB, the thermostat’s job is to help the engine reach operating temperature quickly and hold it steady. When the engine’s cold, it keeps coolant from circulating through the radiator so things warm up faster. Once it’s hot enough, it opens and allows flow through the radiator to shed heat. That stable temperature keeps fuel economy tidy, emissions low, and cabin heat nice and toasty in winter.

Signs the thermostat’s gone crook include slow warm‑up, a gauge that sits low, poor heater performance (stuck open), or overheating and coolant boil‑over (stuck closed). Occasional spikes or erratic temperature can also point to a sticky thermostat or trapped air. Because the thermostat is relatively inexpensive and sits where coolant flows constantly, it’s a smart item to assess during routine servicing.

There’s no fixed replacement interval from Toyota, but many workshops in Aus/NZ will inspect or replace the thermostat preventatively when doing major cooling system work or after 8–10 years. If the bB shows any of the symptoms above, or if the coolant has been neglected, it’s worth fitting a quality OEM‑spec thermostat and new seal. Always pair the job with fresh Toyota Super Long Life pink coolant (premix) and a proper bleed to avoid air pockets.

• Only work on a dead‑cold engine and depressurise the system.
• Drain enough coolant to sit below the housing, remove the housing and old thermostat.
• Clean mating faces, install the new thermostat in the correct orientation (jiggle valve at the top where applicable) with a new O‑ring/gasket.
• Refit the housing, tighten to factory spec, refill with the correct coolant mix, and bleed air.
• Confirm heater performance and stable temperature on a road test, check for leaks under the bonnet.

Look after the thermostat and the bB’s cooling system will repay the favour with reliable, fuss‑free running.

Popular questions about the 2006 Toyota bB thermostat

Does a 2006 Toyota bB have a thermostat and where is it?
Yes. It’s fitted at the water inlet housing on the engine block. On K3‑VE and 3SZ‑VE engines used in the 2006 bB, it’s a wax‑pellet style unit that begins to open around 82°C.

What are the common symptoms of a failing bB thermostat?
Overheating, coolant pushing into the overflow, or a heater that runs cold and a gauge that never reaches normal all point to thermostat trouble. Erratic temperature swings after a coolant change can also mean air is trapped or the thermostat is sticky.

Should the thermostat be replaced during coolant service?
Not mandatory every time, but it’s smart to assess it during a major cooling service or if the history’s unknown. Many techs will replace it preventatively after years of service or whenever the system is opened up, using a new seal and fresh Toyota pink coolant.