I recently purchased a audi A4 B6 2.4 petrol. The problem I have is the coolant starts to pour out of the expansion tank when it starts to get hot. The temperature is ok it doesn't go above halfway. Ive had the water pump, timing belt, thermostat and the head gaskets changed but nothing has made a difference.

I'm lost to what this may be, can someone please help

Hi Harry....welcome to the Forum!

If I were you I would replace the coolant pressure cap on the expansion bottle as this may be the problem if it is not holding pressure.

Very cheap to sort and probably the best place to start.

Let us know how you get on.   Cheers   Trevor

trev ive tried a new cap, but hasn't made a difference.ive also changed the water pump,  (water pump also done by previous owner)
But the problem was still there, i then had the head gasket done with timing belt an all. Checked the radiator for blockages, but still it does the same.
The mechanic has now told me the block may have gone, as someone may have poured cold water in had it overheated as the coolant enters the bottom of the engine.

Easiest way to check is with a temperature gun and point it at various parts of the engine and cooling system as it sounds like a blockage or air lock somewhere in the system.

When you have found the cool spot, thats where the blockage is and where its not circulating...may just need bleeding through or back-flushing the system.

Another route to consider is to carry out a block test with a special tool that most garages have that measures combustion gas in the cooling system...it uses a fluid that changes colour if there is any combustion gas in the system...instant diagnosis!