Always been a problem with the E39 and E53 5 series models. Some of the guys (one a lawyer) on another forum were able to convince BMW to pay for repairs outside of warranty but what they covered depended. Most were told to buy the part and BMW would do the install Free. Some got the entire unit replaced free and others got a 30% discount.

Most 5ers have gone through at least a couple and seems to be a design flaw. I sent mine to VDORepair who fixed mine for $199 and it has been fine ever since. They use better parts so it should last a long while.

Michael