Parts for your 2001 Holden Commodore-Thermostat

2001 Holden Commodore thermostat: what it does and when to replace it

Yes, a thermostat is fitted to the 2001 Holden Commodore. Technical sources including the Holden Commodore VT–VX Service Manual (Cooling System section), GM Powertrain service information for the Gen III (LS1) V8, and application catalogues from ACDelco/Dayco list a thermostat for both the 3.8 L Ecotec V6 and the 5.7 L V8 in VX models. On the V6 it sits in the alloy housing at the front of the intake manifold where the top radiator hose connects, on the LS1 V8 it’s integrated with the water pump outlet housing. So it’s definitely there and doing an important job.

The thermostat’s purpose is to get the engine up to its ideal operating temperature quickly, then keep it there. It stays closed when the engine is cold, helping it warm up faster for better fuel economy, smoother running and reduced wear. Once it reaches its set point (as specified in the Holden service data for each engine), the wax-pellet valve opens to let coolant flow through the radiator and shed heat. If the thermostat sticks closed, overheating can happen. If it sticks open, the engine can run too cool, causing high fuel use, weak heater performance, and gunky oil from never quite reaching temperature.

For servicing a 2001 Commodore, the thermostat isn’t a scheduled “service item” like oil or filters, but it’s smart preventative maintenance to replace it when doing cooling system work, at high kilometres, or if symptoms show up. Holden’s workshop guidance and the aftermarket manuals (Gregory’s/Max Ellery’s VT–VX) emphasise correct installation, sealing, and system bleeding.

• Good times to replace: overheating or slow warm-up, fluctuating gauge, poor cabin heat, recurring coolant loss, or when you’re already doing a water pump, radiator, or hose job.
• Fitting tips: use the correct-spec thermostat for your engine, install a new gasket/O-ring, orient any jiggle pin/bleed hole as per the manual, and torque housing bolts to the workshop spec (don’t over-tighten alloy).
• Coolant matters: refill with the specified long-life red OAT coolant for VX (Holden/GM Dex‑Cool type) mixed with demineralised water if not using premix. Don’t mix red and green coolants, flush if changing types.
• Bleeding: run the heater on hot, top up at the cap, and burp/bleed the system to clear air pockets. Recheck level after the first proper heat cycle.
• Extras worth doing: new radiator cap, inspect hoses, and verify radiator fans cut in as they should.

Popular questions

What temperature should the gauge sit at on a 2001 Commodore?
Once warmed up, the needle typically hovers around the middle. The fans may cycle and the needle can move a touch in traffic, which is normal. If it takes ages to warm up or spikes towards hot on the open road, the thermostat or cooling system needs a look.

How hard is it to change the thermostat on a VX Commodore?
On the Ecotec V6 it’s a straightforward DIY job with basic tools and patience for bleeding, plan an hour or two. On the LS1 V8 access is tighter, so expect a bit more time. Always start with a cold engine, have new coolant ready, and follow a workshop manual for the correct procedure.

Which coolant should be used after replacing the thermostat?
VX models specify a long-life red OAT coolant (GM/Holden Dex‑Cool type). Use a quality brand at the proper concentration (often 50/50 with demineralised water unless premixed). Don’t mix red OAT with conventional green coolant, if switching types, perform a thorough flush first.