1994 F150 4.9L 300 Temperature Gauge
I've had my '94 since it was new and put over 140,000 miles on it (5 speed manual transmission (M5OD)). For the first ten years or so the temp. gauge always stayed between 5 - 10% of the "NORMAL" range - actually below the N in NORMAL. The ambient temperature never mattered and the A/C on or off seemed to have no effect. During the past two years, or so, the gauge has crept up and now usually the needle sits over the O or R - about 40% of the range.
Over the years I have replaced the radiator (due to a leak at the aluminum/plastic interface), upper and lower rad. hoses (as a precaution, not a failure), coolant (water) pump (due to a leak at the shaft seal), thermostat (when the water pump was replaced - not due to a failure) and the drive (fan) belt (every 40k miles or so, never due to a failure). I've replaced the coolant six or seven times (approx. every two years) with 50/50 to 60/40 Prestone and distilled water but I've never used any of those "flush" products. It always comes out looking just like it went in - clean and translucent green. When I replaced the water pump I could see into the engine to the first cyclinder (I could put my fist in there) and the cast iron looked brand new - no scale, corrosion, etc.
What are your thoughts on the temp. increase? Real or instrument error? If corrosion on an electrical connection increases resistance in the circuit would that give a higher or lower reading. If real, what should I check or replace.
Great forum. Any thoughts appreciated.
Last edited by mradclif; 06-28-2006 at 10:00 AM.