Three possibilities that I can think of. The first is that your radiator has an internal leak, allowing oil to seep into the radiator. Many cars have an oil cooling line that runs through the radiator. Most cars with automatic transmissions have a cooling line for the transmission that runs through there too. Over time, these lines can corrode and start leaking. If the car passes compression tests (as outlined below) then you might have this problem.
The second is that your cylinder head gasket is blown. Generally, when they go bad, you will see water in the engine oil and excessive steam coming from the tailpipe. Or if the gasket is blown in a particular area, it could be allow oil to seep into the cooling system and not really allow coolant into the crankcase. Test by renting a compression tester from the local auto parts store. You take out a fuel pump fuse/relay or unplug the coil, take one spark plug out, hook up the tester, and turn the engine over to get a compression reading. Repeat for all of your cylinders and compare the readings to Holden's specs.
The other possibility is that your intake manifold gasket(s) could be bad. This is only in some vehicles and I am not sure if it applies to yours. You would rent a cooling system tester, take the radiator cap off, hook up the tester, and pump it to whatever pressure Holden specifies (maybe 15psi). Then you look/listen for a leak.
As for the clicking sound, I would have to see and hear it to really be able to guess accurately. It is possible that your cooling fan motor has failed and is making that noise.
Sunday, June 4th, 2017 AT 7:32 PM