Looking at a 2000 F150 long bed single cab 4x4 with a v6 with 170k miles. It's your typical rusty Michigan truck. I think it's a 5 speed manual. It has a coolant leak, not sure where. Is there a common place to look for coolant leaks and how hard is it to fix? It also has an exhaust leak I think from the exhaust manifold.

What else should I look for and what fuel mileage should I expect?

 

Yea, if your fluid keeps going low and you don't know where, feel the carpet in the middle of cab under the dash, you might even smell it. It'll be a sweet candy like smell. IF so, it's the heater core. Kind of a pain but far less expensive to diy if you can. Had this issue with my 2001 f150 if not this, check the core hoses going into the fire wall.
If ask if the fuel pump inside the tank had been replaced and when. I would also inspect the front seal area of the rear end for leaks and ask if it's ever leaked or the rear end rebuilt ever and how long ago. Look to see if the u joint look new. I have 160k on mine. These areas I had to address. Everything else has been fine. Oh, listen for ball joint noise, squeaks and inspect upper and lower ball joints. Installed new moog parts at 150k on mine.

 

if 4.2 v6.................intake manifold gaskets or head gaskets..........