Just a quick post..
I LPG converted an early L322 with BMW 4.4 for a guy from the other side of Barnsley from me (over 10 miles away) around 8 years ago, the same owner phoned me a couple of days ago to say it had started losing a lot of water and could I have a look at it please, asked me to give him a call when I had a bit of time. So today I phoned him and he drove over 10 miles to see me, in the last couple of days he's also been using it on the motorway..
As soon as he pulled up I saw loads of steam coming from under the bonnet. Pulled the bonnet and saw the steam was coming from the back of the engine. Removed the engine cover and removed the middle/heater air filter panel on the bulkhead for visibility and access (he's an ex mechanic who now works for a firm that supplies HGV bits but he'd never had the engine cover off and didn't know the middle panel could be removed).
I found a coolant T (for the LPG reducer) had snapped, there was hardly any coolant left in the engine at all. After leaving the engine to cool for some time and after I'd fitted a new T and put the middle panel and engine cover back on I put some antifreeze and water in it and it ran absolutely fine.
He said he has been topping the water up at home and at work but I'm very surprised the engine was still running and wasn't cooked, especially as he'd been on the motorway with it etc, it must have quickly pumped all it's coolant out due to the severity of the leak.