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possible to install a thermostat backwards?

cerberusaardvark

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So after running my top end rebuild for almost 5 miles, last night it occurred to me maybe the reason my temp gauge seems weird to me is because I may have installed the thermostat backwards.
Yesterday I was looking in the engine bay after a day of driving and normal operating temps and I noticed the coolant in the overflow box was above the cold fill line. I thought that's weird, when the engine is at optimal temp shouldn't most 94 the coolant be in the tube running? And when the engine cooled down, the level in the overflow box dropped to below the cold fill line. I thought, wouldn't it make more sense if when the engine is running cool it would push more fluid into the reservoir so the engine would warm up faster?

Or maybe my understanding of how the coolant flows is wrong. Engine starts, running rich to heat up, less coolant to retard rising temps, then engine leans out at normal temp, more coolant required flowing to maintain 190 degrees.

Not sure but mine seems to do the opposite, which might make sense if the thermostat is opening and shutting on the wrong side? Idk, looking for advice.
 



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If you installed the thermostat backwards, it would probably not open up enough to allow coolant to flow, and the temp gauge would shoot up into the far right range, the engine would overheat, etc. etc.

The thermostat on the OHV V6 installs with the spring IN the lower manifold:

IMG_0785.jpg



The 'cold fill' line is just that - the level the coolant should be at in the overflow reservoir when the engine is cold, as in, has sat overnight for several hours.

When the engine is running, it draws in coolant it needs from the overflow tank, or pushes out coolant it doesn't need to the overflow tank.

When the engine is first started, with the engine cold, the thermostat is closed, and it doesn't open until the engine reaches operating temp - around 190 degrees, which opens the thermostat and gets coolant flowing.

Since the steel block and heads and the aluminum manifolds expand as they heat up and contract as they cool, and the coolant/water mixture does the same, under pressure, there has to be some way to allow the volume of coolant to vary under these conditions - otherwise the pressure would have nowhere to go and the engine would crack under the pressure. So the overflow tank provides a way for the engine to only have as much coolant as it needs.

As long as the coolant level is at least at the 'cold fill' line when the engine is cold, and the coolant/water mixture is around 50/50, things should be good.
 






cerberusaardvark

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ah ok. in that case i may have a phantom coolant siphon going on bc it seems no matter how many times i fill to the cold fill line, a few weeks later when i check again it always drops down to about an inch or two below and stays there steadily.

even though my temp gauge tells me when im accelerating uphill at 2500 rpms i go from the r in normal to the a in normal over the course of about ten seconds its not an indication of a malfunctioning coolant system? im just paranoid about engine overheats as i would love to meet up one of these times out in the desert with everyone else. i feel like if my engine gets to the a in normal going up a hill on a street then it would overheat going up any sort of grade off road in desert weather.

also how does the fan clutch work? i put on the one that people reccomend, forget if its the the hayden or four seasons severe duty fan clutch on and i definitely hear the difference, but does it spin the fan faster when the engine heats up more quickly than the thermostat can adjust for?
 






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If the system is losing coolant, it could be anything from a blown/leaky head gasket to a loose hose clamp on either the radiator or heater hoses.

If the engine temp gauge needle moves like that, that usually indicates a weak thermostat spring - or a thermostat that is having trouble maintaining a solid 190-195 engine temp. It can sometimes be the coolant, if the coolant is old and has lost some of it's heat transfer ability or if the metals are no longer being protected and there is some buildup or sludge or corrosion/rust in the system, especially in the radiator.

Sometimes it just happens when the outside temps are really hot - so you really need to judge cooling performance by a range of conditions, both when it's mildly cool/warm and not just when it's super hot.

The fan clutch works by "locking up" or engaging the fan more, driving it harder and faster to move more air through the radiator, to work with the thermostat to keep the engine temp in check.

When the engine is cold and first starts, the fan clutch is usually not engaged very much, and can thought of as almost freewheeling, not moving much air. When the thermostat is fully open and the engine still needs more cooling, the fan clutch should engage more and more up to it's maximum amount to aid cooling and prevent engine temps from going past the L in NORMAL.

If the fan clutch can't keep up, it's the wrong one for the vehicle, or at least with that engine/trans combo in that environment. Standard duty fan clutches are generally for manual transmission models. Heavy duty fan clutches are generally for automatic transmission models. Severe duty fan clutches are for hot conditions like the southeast US or where temps are regularly over 100 degrees and max cooling ability with A/C is a must.

A standard duty fan clutch on an Explorer with an automatic transmission will usually be constantly engaged at it's upper limit to provide enough cooling. It might work ok in cooler climates or in winter weather, but in hot temps, it will not do enough.

I'd say a motor that goes from the R in NORMAL to the A in NORMAL when going up a hill is pretty normal, if it's doing so on a warm/hot day with the A/C on. At the very least, if the thermostat was in backwards, it wouldn't be cooling nearly that well.
 






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