4N1M4L Posted June 6, 2017 Share Posted June 6, 2017 So today drove 26 miles home from work, no issues noted. Stopped at the gas station to get the wife some cigarettes. on the 2.5 miles home the air quit blowing cold. Checked gauges, over heating. Eased it home. Radiator cap is off, overflow bottle is empty. Fill it up, start hearing this knocking noise, almost like a relief valve lifting at the power plant. Eventually things calm down. Turn on ECU, temp normal. 200. Idle for 6 minutes, temperature climbs to 240. Bottle starts coughing and spitting. Shut down. To me it sounds like the thermostat is shut, but I don't know. Anyone know how to tell the difference between water pump and thermostat problems on these 3.5L engines? Quote Link to comment Share on other sites More sharing options...
drolds1 Posted June 6, 2017 Share Posted June 6, 2017 If your current t-stat is a Motorcraft unit, they're fail-safe, i.e, they're designed to fail in the open position. So it's most likely not the t-stat. Is your cooling fan working? I know it was about 109º in PHX yesterday (my son lives in Gilbert). It wouldn't take long to overheat with the A/C on under those conditions without the cooling fan. Any coolant on the ground? How did the coolant level get so low? How many miles on your car? R2D2 and 4N1M4L 2 Quote Link to comment Share on other sites More sharing options...
4N1M4L Posted June 7, 2017 Author Share Posted June 7, 2017 185K miles. it was the thermostat. The rubber got flakey, and part of it got stuck in the valve area. it doesn't open when heated. thankfully it was this and not the water pump Quote Link to comment Share on other sites More sharing options...
drolds1 Posted June 7, 2017 Share Posted June 7, 2017 Glad to hear that. These engine have internal water pumps and replacement requires that the engine be removed. It's a $2G+ repair. Quote Link to comment Share on other sites More sharing options...
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