hey, as it says, i've got rust in my coolant bottle, water usage is about once a month i'm filling up, and the cap has powdery surface rust. i'm guessing head gasket?
oil changed a fortnight ago, seemed fine, just the usual old oil, no milkyness or anything.
cheers.

Hey mate, I had rust in my coolant reservoir, and throughout my entire motor because the previous owner ran it only on tap water....

As for the water usage, is it leaking anywhere? Or any white smoke in the exhaust or milky oil?

Losing coolant at that rate doesn't sound like head gasket. When mine went, I had to top up the coolant every day. There are a hundred other places coolant likes to leak from: rad hoses, heater hoses, heater tap, heater core, coolant pipe from back of water pump, water pump itself, radiator, thermostat housing, etc. Put it up on ramps or stands after a drive up to normal operating temperature and take a good look around with an inspection light. If it IS the head gasket, you are most likely to see coolant running down the block under the exhaust manifold (or stains from it).

As for the rust, that's chronic in the Falcons - cast iron blocks will do that. It just means there wasn't enough (or any) rust inhibitor in the coolant. I use 1/4 to 1/3 Prestone and don't get any rust, but the reservoir will be permanently stained. After you have fixed the leak, use a good radiator flush product, thoroughly flush out the whole system (incl heater) and fill with at least 25% quality concentrated coolant (not the premixed stuff - that's only for topping up).

having rusty water in it and loosing coolant could be the dreaded head gasket,
but im thinking it could just be rusted out welsh plugs.. the worst thing for these engines is straight water. .

bahaha, aww no.
i've only been using straight tap water, only due to not knowing what has been in there and what i should be putting in. also being too lazy to ever drain and replace.
i'll make a start with coolant, can someone give me products i can pick up from supercheap or whatever, i'll drain and do it saturday.
if its the headgasket i'll have to sort out getting it done, but atleast i'll be on top of the coolant situation anyway. (well a new start)
and i'll suss out any stains.
cheers.

Just go to Repco and get 2, 500ml bottles of concentrate inhibitor.
Empty out what water is in there, and put the 2 bottles in and top up with tap water....it will be right for about 2 years.....or until such time as you find/fix the leak.
Here's where the welsh plugs are located that you can see.....there is 1 at the rear of the block that you can't see.....they are all the same size....40mm.

 

 

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ive always use disilled water or premix subaru coolant works a treat in the old xe running the eb on distilled water and concentrate but i over dosed it a little. and i added a canister of silverseal to th radiator just to block up any leaks

Mate if you haven't purchased yet.
Go to auto one or super cheap auto and buy the reccommended NULON brand coolant.
Then find out the mixing ratio with your car model

I reckon your water is disappearing due to having wat too much water itself in your block.
It's only gunna evaporate when heating up.

I could be wrong

If its using water you have a few options.

evap? pfft its a pressurised cooling system.

1: head gasket
2: overflow cap
3: welsh plugs
4: external leak

Do as cjh said. But I strongly doubt it'll last 2 years if its 'using water now'
However adding glycol or simular inhibitor will enable you to at least 'smell' or see the leak.

Usually a falcon with an external leak (welsch or head) will start to pressurize and leak 10 or so minutes after stopping maybe you'll see a dribble down the block imbetween 5/6 cyl.



and in no particular order.

I ran my car for 3 years with distilled water...worked fine for me until I fixed that dreaded leak behind the water pump. It has been running on coolant for a year now...but barely gets started so it was a good idea to reduce the rust.

Personally I'll pull the radiator out and give the whole system a flush with tap water. Then put just water in to see if it's leaking, then coolant.