along with what bandook suggested, check the length of the grounds themselves. a breach in the insulation= moisture and salt( i think illinois uses chloride now,too? that stuffs worse than salt) getting in there and wreaking havoc.
you can also hook up an ohm meter to the coolant temp wires and start wiggling them while its running. a meter with sound helps here. easier to just listen than to have to keep an eye on the meter.