Overheated and hole in expansion tank
 

Car is 2004 3.0i petrol. I was towing a trailer with a car on the other day when I noticed the needle rising then coming back down a few times. It did this for about 30 minutes then when I can to stop all the coolant came out and there’s was steam everywhere. Once cooled down I Noticed a 1 cm hole in the side of the expansion tank. Is this a common fault or did another issue cause the expansion tank to blow? It’s currently in the mechanics being looked at which is 6 hrs from where I live..

The ET on the M54 is a weak point for sure. It is usually the first component to give up. Depending on your mileage, I would consider a coolant system refresh with a new ET, WP, thermostat and associated hoses. If the budget allows I would also consider the fan clutch and fan on the engine.

Hard to say. Expansion tanks get brittle with age and with a consistent 20 psi (2 bar) of pressure. It can just give way. At the same time, if exhaust pressure got in the coolant flow, that can cause excessive failure. Since it's easy and cheap, you might have mechanics test for presence of exhaust in coolant, just to rule it out. If okay, I would replace cooling parts, bleed the system and carry on.

But 30 mins of up/down temps? - At the first sign of coolant temp irregularities, you should have stopped and investigated, particularly when pulling a load.

Common issue (expansion tank)...

Do a compression test, if OK, then search forum for "cooling overhaul"...