I need a straight answer as I've got myself going round and round 
I have a 13yr old SUV, used as a family car - had it for 5 years, over the last 6 months I've spent around £600 on it (servicing, had a tow bar fitted and front brakes all replaced) jobs a good un I thought until 6 months from now when MOT is due, plan was to MOT it then sell with full MOT privately - eBay or similar. Except it's started to make a mystery noise at a certain speed, mechanic suspects it's a gearbox problem - it drives fine but just has this new noise. I was due to take it a gearbox specialist but I've been told if it needs work then I'll be without a car for 4 days and it'll be approx £800 to spend (I think car is worth £1500 max maybe? 140 000miles on clock)
But I also have a Discovery which is currently off road and needs £1200 spent on it to get roadworthy (was my tow vehicle hence having new one put my other car) - scrap value is probably £1500?
What would you do? Fix current car, drive it til MOT time then sell before MOT and sell Discovery too to buy a new vehicle from both sales or sell both now without investigating mysterious noise on current car? Being without the car for 4 days will be a pain in the arse as well as I live rurally.
I have a budget of £5k plus the proceeds from two current cars to spend (I won't get a car on finance). WWYD wise MNers? New car must be strong enough to tow a horse box.