Help....coolant everywhere

[CerbieMR]

Had my new Griff for about a month. Has been driving wonderfully...however...
Just got into the car, thought I had warmed up the engine (left it idling for about 5 mins) then took it for a 20 minute blat. I got home and it has dumped a load of coolant out of the aluminium expansion bottle onto the driveway. I have tried to unscrew the cap and it is continuing to spew everywhere...
Diagnosis??

[paul2000]

just a guess but the top is not cross threaded is it if he top is ok ,no way should it leak

[CerbieMR]

Dont think it was. Engine cooled down. I have opened the cap and the coolant level is right on the brim. I have screwed the cap back on and run the car for about 15 minutes on the drive. Engine was thoroughly warm and I brought the revs up to about 2000 for a few minutes. Fans were working fine, engine temp gauge ok and no more leaks...so I am at a loss as to what caused it.
Any other suggestions welcome!

[GreenV8S]

Leave it to cool down before you do anything else, that water is under pressure and hot enough to scald you badly. In general, you don't want to be doing anything to the cooling system while it is hot and under pressure. Letting the pressure out won't do you any good since it will chuck coolant out when you do that and you won't be able to refill it until it has cooled down anyway.

It sounds as if the engine has overheated. When it cools down, check the coolant level and top up as necessary. If it's lost a lot then use the correct strength anti-freeze mix, if it only needs half a liter then plain water is OK. Make sure the cap screws on easily and holds pressure, check that the fans come on correctly when it comes up to temperature.

[CerbieMR]

thanks for the last, you were probably penning that just as I was. Everything seems to be running okay now.

[bluebottle]

As greenV8 says always let it cool down fully before opening..As the temp was ok and it only belched a bit of water out, it could have either been an airlock in the system or you over filled the expansion tank.
The swirl put (if you have one) should be full to the thread, but the swirl pot should be about 1 1/2 to 2 inches below the rim. It varies from car to car where they prefer it my first Griff didn't like anything over half full and would belch it out.