Water level in the reservoir keeps going down , I top it up between the MIN & MAX lines.. occasionaly it spits the water out the overflow tube.

The other day I topped it up , went to work - 50km drive - parked it - end of the day came back , nothing under the car..
Drove it 6km to Dan Murphys, came back out to find a heap of coolant under it.

Temp gauge never goes above half and thats only when its standing still. driving along it is close to the 'C'.

Sometimes I am topping it up after NOT seeing any coolant leak.

A friend suggested HEAD GASKET .. but no water in the oil and no oil in the water.

With a previous 6cyl fairlane i had success putting a bottle of the brass powder 'head gasket' repair stuff in.

He suggested to do that and see if it stops losing water.
He says I could be losing the water straight out the exhaust...

I dont see any obvious leaks under the bonnet..

The overflow tube leak has only happened twice (that i am aware of) in two weeks.

In the last week I have topped up with nearly 5Lt of coolant.

Car has done about 112,000kms

Unless its already done a headgasket, it sounds like its time for one.

Try replacing the tank cap incase the old one has gone s**t and spewing it out the overflow hose.

Oil in the water is 1 of 3 headgasket scenarios, the other 2 can be tricky to find. But look at your coolant tank and coolant. If you start having black floaties in the water or the bottom of the tank becomes black it generally means the gasket is leaking exhaust gases into a water jacket.

If one day its good and the next it spews water out the overflow its also a sign the cooling system is being pressurised by the exhaust and the cap is releasing the pressure. If this is the case, when you do your head gasket, it would be an idea to change ALL the cooling hoses.

Another idea would be to pull all the sparkplugs and see if any are rusty at the ends. Or turn the motor by hand. If you can see the top or sides of the pistons are clean, then chances are its slowly leaking water into that cylinder.

mmmm.... I just had this problem...

I was putting a full tank of water in per 20min drive. Mine has done 240,000ks and still on it's first head gasket(From what me n my uncle can tell...)

I thought it was the head, but same as you, No water in oil n no oil in water.

If you can, drive it up some of them ramps or wood so you can get a clear view under the car. Poking out of the firewall is a little Pipe with a 45o cut on the end.

Run the car till pressure in the hoses, then turn off. Lay on a mat and wait for a few mintues... Eg 1 to 5 min. (I'm told the car will get more pressure after sittin for a bit)

If water comes out that pipe then it's gonna be ur heater core.

The pipe is one the passenger side if you don't know. Black, about 2inch long...

Hope you find your problem...

I'm not sure what to think anymore.

I'll have to have a good look this weekend.

After work today I noticed what could have been todays coolant puddle under the car (I usually park in the same spot in the undercover carpark)

Started it and sure enough the reservoir light came on ..

I though well i'll drive it to Dan Murphys and pop the hood and see if i can see any leaks while its running.

Dans is no more than about 6kms drive from work , 'some' heavy traffic and 'stop starting'.

I thought i could see a wet spot at the head on the pasenger side of the motor, it looked fresh. I looked under the car and saw nothing else suspicious.

So, i stopped the engine, cracked the radiator cap, towel in hand, intending to let the pressure out and top it up.

It spat a bunch of coolant out.. it was boiling... eventually i took off the cap right off & let it spill the coolant out all over the ground (with the towel diffusing the gushing)

A mechanic from Fords happened to come over in the car park and had a quick look he said 'thermostat is stuffed'.. thats all i got out of him.

Once it stopped I started it again and began filling it with tap water , no more coolant on hand.
It took 5 ltrs of water.

Thing is on my drive home on the Motorway.. the car seemed to run slightly warmer than usual.. and temp gauge came up faster than usual when stopped for a minute or so at the lights.

(usually runds cold and temp goes up to half if i am idling for 5 mins.)

An hour after being home there is no evidence of the overflow dribbling anything on the concrete.

If the thermostat was stuffed, wouldn't it be running HOT all the time?

I remember an XW V8 Fairmont I had once..
If the temp gauge went up to just half, it was HOT.

I am wondering if i might have similar temp situation in this car.

Both ur fans work?

I also had a blown fan relay. causing it to get hot in traffic...

Yeah, pretty sure both my fans are working.

Just got off the phone with a pretty cluey mechanic mate of mine.

He suggested taking the plugs out
starting from the back one as soon as the plug is out in my hand to poke a screwdriver in the cylinder for 3 seconds and pull it out.
Look for condensation on the screwdriver, wipe it with my finger & see if I end up with a drop/ drip of water.
Do each plug..

He reckons if they are dry then its not head gasket but he seems pretty sure its my head gasket.

sigh.

I'll do that on the weekend.