Two very similar GM references can identify different parts. In the comparison here, 12678780 identifies the thermostat housing, while 12678779 identifies the separate pipe and water-outlet assembly. A one-digit difference is not a reason to treat them as interchangeable names for the same package.
Start by asking which component the workshop has identified as necessary. Then check the vehicle application and the contents of the actual offer.
Which ZB application is covered?
The ZB 3.6L thermostat-housing product page is limited to the listed LGX V6 petrol all-wheel-drive hatch and wagon applications within 10/2017–12/2020. Four-cylinder petrol, diesel and earlier Commodore series are excluded.
The selected package is the thermostat housing assembly with the thermostat and black sealing gasket shown. It does not include the long coolant pipe or water-outlet assembly.
Compare the housing, spring and mounting interface
Match the original reference, housing profile, spring assembly, two-bolt mounting and seal arrangement. Compare photographs from the same direction and check the complete package description alongside the image.
Do not infer that an adjacent pipe, outlet or every installation item is included just because those components are related in the cooling system. Confirm the workshop’s full parts and service requirements separately.
Read the GM references in context
The official GM service bulletin PIP5940 distinguishes the thermostat housing from the pipe/water-outlet assembly using the two references above. That distinction is useful for identifying the component; it is not a blanket fitment statement for every vehicle using an LGX engine.
A later catalogue supersession also needs to be checked for the actual vehicle and supplied assembly. Keep the linked product’s stated reference and Australian application scope in the comparison rather than substituting a similar number on assumption.
Make the parts enquiry precise
Send the VIN, build month, ZB and LGX identification, original reference and accessible photographs of the component the workshop needs. State clearly whether the enquiry concerns the thermostat housing or the separate pipe/outlet assembly.
A reference comparison does not diagnose the cause of a temperature or coolant complaint. Use the workshop’s diagnosis and vehicle-specific service information for the repair, including any additional seals, fasteners or filling requirements. The product link provides the exact supplied configuration and current availability.
Prepared from application records, catalogue checks and the linked product photographs. The featured workshop scene is an AI-generated editorial illustration. Information reviewed on 3 November 2026.