SORRY again Dustydog but.
Again you post something that is akin to scaremongering : "The X5 cooling issue" What cooling issue? The car comes with larger fan for quicker cooling when a factory fit tow bar was specified and at no cost.
As your own link showed, there appears to be little evidence of any over heating issues with X5 with retro fitted tow bars and no fan upgrade. When towing a number of issues can arise with any brand of car. Auto gearbox cooling has been a long term issue, suspensions, gear box and clutch, dual mass flywheel, and then there are concerns over towing with the new double clutch style auto box's.
I've been driving 3litre 3 and 5 series BMW's solo for a long time, the 3 litre inline BMW engine is rated as one of the best in the world. On the X5 there were a few problems with cracking exhaust manifolds some time back, those were addressed a while back and the engine gets a revison upgrade version in 2011 as Tri-turbo with 700nm of torque and about 345hp. If there was truly and engine weakness a completely new engine would be the long term cheaper option for BMW.
Used X5 can offer well speced comfortable tow car option and there are quite a lot of people who choose to go that route and with retro fit tow hitches not many seem to bother with cooling fan upgrade nor are there legions of reports of X5's overheating.
For anyone contemplating an older used X5 that hasn't got a tow bar or upgraded cooling fan, there is a good chance they will be going to Towsure or an after market fitter rather than pay Beemer dealer top $, after market additional cooling fan (if they feel it is needed) will cost less than others pay for suspension upgrades on family saloon tow cars.
Re: MichealE, Dealer out of order if it was a NEW car, I was quoted £1095 just for Mercedes Tow hitch and wiring 4 years ago.