The Mid 2007 MacBooks only have a single fan. It is located in the center towards the display hinge - about where the Num Lock and 6/7 keys are.
I believe the first error 4MOT/1/4000002:exhaust is related to the fan. There could be a lot of dust/foreign material blocking where the fan is held in place by tape to the exhaust fins on the heatsink. I do not recommend removing the heatsink, but you could try removing the fan and blowing out any foreign matter from the fan area and exhaust fins.
The second error 4/MOT/2/40000004:Center-lower-front is a bit tougher. I would guess it is a temperature sensor. If the fan is blocked , the entire machine could overheat, especially after an extended stress test due to heat build up.
iFixit - MacBook Core 2 Duo
Again, they haven't blocked Snow Leopard. I will try to install Snow Leopard on one of my old Macs and see what happens.
I wonder if it might be prudent to try different version of Mac OS X? It can support from 10.4.11 Tiger to 10.7.5 Lion?
C