My Exploder is doing something odd, or at least new to me and wondering what the cause is.

On every vehicle I've owned with an overfill tank, the tank levels off to "cold" level after driving...in other words there are two conditions I see it in, "hot" & "cold".

This truck, however, is odd. Sometimes after driving it and it sitting, after it cools off I check the level in the fill tank and it's clear up near the top. When I check the radiator, it's low. If I drive the vehicle, it draws from the tank and goes down. Sometimes when cold it's at the "cold" fill line and the radiator is topped off....other times not.

What's causing this, and is it something I should worry about? Might be something really common, but I've never experienced it.

TIA

Replace your radiator cap and see if that doesn't cure it.

Stuck Thermostat maybe? Not letting coolant to move the way its supposed to. Does the temp fluctuate at all?

Quoted: Stuck Thermostat maybe? Not letting coolant to move the way its supposed to. Does the temp fluctuate at all?

Yeah, it does go up and down but it always has and I've replaced the t-stat twice with good OEM ones, and checked them in boiling water to make sure they open correctly. I've been told it's really common on explorers.

The fluctuation isn't big, tho....moves maybe 1/8 to 1/3 of the meter.

Quoted: Replace your radiator cap and see if that doesn't cure it.

Brand new OEM cap on it. That was the first thing I tried.

Quoted: Quoted: Replace your radiator cap and see if that doesn't cure it. Brand new OEM cap on it. That was the first thing I tried.

Well then how about the overflow hose? Any cracks in it?

New hoses, new T-stat, new radiator cap, etc.

Bump for daylighters.

I guess my real question is, what would cause the engine/radiator, as it cools off, not to create a vacuum and draw in the cooler resevoir fluid? Shouldn't it, as the engine sits and cools, draw that back into the motor to the "cold" line again?

The only thing I can think of is a leak somewhere, but I don't seem to have a leak anywhere.

?? So confused!

Quoted: Bump for daylighters. I guess my real question is, what would cause the engine/radiator, as it cools off, not to create a vacuum and draw in the cooler resevoir fluid? Shouldn't it, as the engine sits and cools, draw that back into the motor to the "cold" line again? The only thing I can think of is a leak somewhere, but I don't seem to have a leak anywhere. ?? So confused!

Check the hose clamps , especially the Mobia spring type clamps .
Clean the necks of any corrosion/deposits and reinstall .
It's not unusual to find spring clamps that hold pressure
but leak under vacuum .

Another thing , depending on the year and motor is leaking
intake gaskets .

The bad thing about the 4.0 . Even though it's one of fords better
motors is that they tend to use coolant their whole life . So you are
always topping off the coolant .

Quoted: My Exploder is doing something odd, or at least new to me and wondering what the cause is. TIA

Well atleast you know what your driving.