Hey guys, hope you're all well.

I'm after some advice as usual...The engine in this car that supposedly had a cracked head is a bit of a mystery. If I can list a few symptoms and if anyone has any ideas or suggestions please let me know.

When I went to see the car, we left it at idle to warm up. It took about 20ish minutes and the temp gauge was only on half way, but the water in the expansion bottle was clearly boiling and you could stop the viscous fan with one finger. Apparently the thermostat had been replaced the previous year, so why did it not register that the water was boiling in the bottle (ie overheating on the needle), regardless if the fan was running properly or not!? is it a possible blockage in the cooling system, or air lock maybe?

Well anyway this problem has led to their being a serious overheating problem, and at some stage whilst overheating the head gasket has split or the head has cracked. Meaning you could clearly see water coming out of the exhaust and you could smell a hint of oil as well. Inside the oil cover their is some creamy mayonnaise which means their is definitely some sort of water problem!

Is this likely a cracked head or head gasket and is their any easy way of testing it without having the head whipped off and pressure checked? If the water pump blows do you find that the water will boil in the pipes, etc...

Can any wise owl help me make the decision on this one. The car is gorgeous and in immaculate condition. By the way, the guy selling it laid all his cards on the table he didn't try and fob me off, he told me absolutely everything and is selling the car as "faulty".

and lastly does anyone know where I could source a running M50 with VANOS (engine code 20 6S 2) with about 100k on the clock and at a reasonable price (with delivery) have tried fab direct (fab bmw) Do any of you guys own a breakers? Please let me know I would be very interested in your prices.

Thanks for your time...again

Sounds like the initial symptom which you described was the early stages of either a failing head gasket or cracked block/head.

The bubbles which you see in the expansion tank are likely to be due to combustion gasses entering the cooling system, and not boiling coolant. This is why the temp is normal.

This usually causes overpressurisation of the cooling system and the coolant can then be blown out via the pressure cap. This can will lead to full on overheating and further damage.

Sounds like trouble, only option is really to strip the engine and inspect / pressure test the head and block.

I had a similar fault on a new Cooper S the other week - it was due to a cracked head and only occured after about 10 mins hard driving - probably once everything had expanded.

Hope this helps...