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Are coolant leaks common in 2015 Holden Commodores?

Asked by Allan

There is a slow coolant leak between the motor and transmission in my 2015 Holden Commodore. How common is this problem? Apparently the exhaust system and transmission have to be removed to fix the leak?

Answered by CarsGuide

10 Aug 2021 David Morley

This is not an unknown problem with Holden’s Alloytech V6 engine and can often be traced back to a damaged gasket for the thermostat housing which is located at the rear of the engine block. And you’re right, to change this gasket which costs just a few dollars, involves removing the exhaust and transmission. The best advice is to have the thermostat itself changed while all this work is being done, as it will save you going through it all again if the thermostat ever fails (and they have been known to).

But definitely have it checked out as coolant leaks never fix themselves and a small leak today could easily be a big leak tomorrow, leaving you stranded with an overheating engine. Meantime, you might be lucky and discover that the leak is not from the thermostat housing at all. These engines are also prone to coolant leaks from a pair of O-rings at the front of the cylinder heads which can allow coolant to leak through the valley and out the back over the transmission tunnel, making you think the leak is from the rear of the V6. Don’t rule out the water pump as a source of leaks, either. The trade seems to think about 100,000km is the lifespan for an Alloytech V6’s water pump.

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