If the car has been running at a higher temperature than expected, then it is always going to cause problems. If your engine is the BMW engine, its hoses are held in place by rubber o-rings with clips on the outside. Once these rubber o-rings start to break down (usually because of poor coolant mixtures and/or high temperature) then it will just leak more and more as the system can't hold its pressure.
As an example, a customer of ours recently purchased a 4.4 M62 engined L322. The water pump showed signs of leaking and he had coolant loss. He took it to the local dealer who told him that the pump was fine and he just needed a new radiator fitted. He has the work done, but continued with the same problems. He let us look at the car and it was obvious that the pump was leaking slightly, and that someone had tried to attempt a repair by smack the
[email protected] out of the viscus nut trying to get the nut off as there were chisel marks in the nut.
When we got the pump off, it was obvious that the problems were worse than expected. The M62 has a water manifold on the back of the engine, and 2 pipes run from the back of the pump to this manifold. The O-rings in the system were shot and there was coolant leaking past the manifold at the back, such that the bolts in the back of the heads were rusted in place, one breaking off when we tried to remove it.
Investigating further, the electronic thermostat had broken and probably probably just as well in a position where it was letting coolant fully circulate. Deposits similar to a glazing effect were present all over the metal, probably as a result of unclean and incorrect/poor coolant.
This was close to a 1k job, but at least it appears to have solved the problem. Seeing Microcat's 12k for an exchange M62 engine, it is probably worth getting it checked out before it all goes wrong. I'd also suggest getting the new coolant (non-OAT type) from the dealer. You'll get a good price for a bulk 20 or 25L buy.