I usually weigh major repairs by how many payments on a replacement vehicle they would represent, especially after the vehicle is paid for. Say I need a $500 A/C repair. Buying a truck, assuming I find one exactly like the one I have, to replace it would require a monthly payment of around $400 a month, give or take. So that repair is the equivalent of just over one monthly payment. That's nothing. Certainly not enough to justify a new purchase. Now, once you cross 150,000 miles, it becomes harder. At that point, a $1000 repair may not be worth it, depending on the vehicle.