Temperature gauge drops when going downhill in gear
tknowles
Band Wagon
I have searched for the answer to this and haven't found any posts. Hope this isn't a duplicate..
'90 2wd 5sp
When I'm going down a long hill and using the transmission to slow me down, the temperature gauge drops. If I shift to neutral and just use the brakes to slow down the gauge will slowly go back to normal. I think the engine is actuallly cooling down, as it seems cool in this condition. I have replaced the thermostat and the temperature sending unit checks out fine.
I guess it's not that big of a deal, but it's probably not good to be running cold right? I'm hoping to figure this out by the time winter rolls around again - it's definately worse in winter.
Thanks Wagobuddies
'90 2wd 5sp
When I'm going down a long hill and using the transmission to slow me down, the temperature gauge drops. If I shift to neutral and just use the brakes to slow down the gauge will slowly go back to normal. I think the engine is actuallly cooling down, as it seems cool in this condition. I have replaced the thermostat and the temperature sending unit checks out fine.
I guess it's not that big of a deal, but it's probably not good to be running cold right? I'm hoping to figure this out by the time winter rolls around again - it's definately worse in winter.
Thanks Wagobuddies
Comments
When going downhill in gear with the throttle closed, zero fuel is being injected into the engine. As such, the primary source of engine heat (combustion) is absent. At the same time, there is plenty of air flowing through the radiator reducing coolant temperature.
As for 'running cold,' I wouldn't worry about it unless the engine rarely reaches operating temperature. As long as under most operating conditions the engine reaches normal operating temperature, your thermostat is working as designed. Under certain rare circumstances (e.g. coasting downhill in gear, at high speed, with the throttle closed) the engine is not producing enough heat to maintain 180 degrees. But if you take it out of gear, the engine must start injecting fuel to maintain idle speed. Under that circumstance, it will likely produce enough heat to maintain 180 degrees.