Situation - put an AU motor into my EL about 6 months ago with new thermostat.

One or two days ago, the low coolant light illuminates so I pull over and find heaps of coolant leaking from under the car, from the thermostat housing O-ring seal and from the metal pipe that goes into the base of the thermostat housing.

I top it up, leave the overflow reseviour cap on the first click so no pressure builds up and drive home with no problem.

I haven't had the bonnet up for a few weeks so its not something I've touched recently.

There's no oil in the water, water in the oil and no bubbles in the coolant while the engine is running.

I am 99% sure its just a f**k radiator cap, even though it feels OK and has some spring pressure and moves without sticking.

Any other common problems that can cause everything in the cooling system to s**t itself all of a sudden? I was on cruise at 100km/h on a highway when I noticed it happen, weather was around 20-22 degrees, doing absolutely nothing to stress the car.

So, under the car the coolant busted the heater tap and thats where the other leak was coming from.

Other possiblities?

Just deterioration of the tap IMO. Plastics + heat & coolant tend to get a bit brittle.

Other possibilities of course are many... had gasket allowing cylinder pressure into cooling system etc. You can have the system pressure tested at any workshop worth its salt.

Replace the s**t that's busted/leaking and go from there.

I can't exactly test the pressure when there are a few places that are leaking, I need to patch them up first before I connect a pressure test to it.

There's no need to take a car to a workshop to pressure test it, just get an old radiator hose, cut it in half with a bit of metal inbetween and a tyre valve poked through a hole in the metal will do what any pressure test can do.

My question was can anything cause all three to fail simultaneously? I understand if the HG has failed (and hope its not, I'll be p****d if I have to do the HG when I'm about to get a better car), I'm just after info if something else can cause it. Not that I know what could though.....