1996 Explorer Eddie Bauer thermostat

[chuck1022]

I put a new thermostat in my Explorer. 190 degree or what ever the factory calls for.

The temp wanders now where as my other Explorer is rock steady and never moves.....same as my wife's car, rock steady.

I have Burped the coolant system...it never overheats.

Anyone one else have this issue?

The pictures below are the high and low movements.

View attachment 20230330_080610.jpg View attachment 20230330_080619.jpg

 

[donalds]

Could be a bad thermostat or temp sensor imo

Can you use the search function above to find threads on both problems
I'm leaning towards sticking thermostat right out of the box

 

[410Fortune]

Well hold on now

Do you have a scanner?

It is very possible what you are seeing is the thermostat open

the water temp reaches 195 and the thermostat opens the rush of coil water then causes the gauge to drop

Does it continue to fluctuate after the initial rise and drop?

What brand thermostat did you install? Not all thermos are created equally these days. Stant super stat is what I run

If I get a sticky one like you suspect you can remove it and boil it in water on the stove with a thermostat and see what temps it works at. You can take 4 t stats frim
The parts store and they will all open at different times it is ridiculous quality control in this day and age


Weep hole points up (if it has one) and the spring always goes towards the engine

After you change the Thermostat it is common for air to be trapped behind it which is what the temp sensor is reading hot air… until all the air is burped which can take several drive cycles (4.0 ohv known for this) you will see these wild fluctuations

If air is trapped behind t stat on the 4.0 ohv you can boil some water and pour it down the upper radiator hose holding the hose up high
Or I believe some of these guys will say to jack ip the rear end way up and run it but don’t quote me on that

The reason I asked if you have a scanner is because there are two temp sensors one for the dash and one for the computer it would be interesting to see the coolant temp on the computer side of things

 

[chuck1022]

Well hold on now

Do you have a scanner?

It is very possible what you are seeing is the thermostat open

the water temp reaches 195 and the thermostat opens the rush of coil water then causes the gauge to drop

Does it continue to fluctuate after the initial rise and drop?

What brand thermostat did you install
Weep hole points up (if it has one) and the spring always goes towards the engine

After you change the Thermostat it is common for air to be trapped behind it which is what the temp sensor is reading hot air… until all the air is burped which can take several drive cycles (4.0 ohv known for this) you will see these wild fluctuations

The reason I asked if you have a scanner is because there are two temp sensors one for the dash and one for the computer it would be interesting to see the coolant temp on the computer side of things

It fluctuates the whole time you drive. Never gets hot. I do not remember the brand. It's a simple swap. I will put another one in.

 

[410Fortune]

0hv 4.0?

Gauge was working before stat?

I lean more towards trapped air then a faulty t stat with the wild gauge fluctuations

Seriously, basically everytime I change an engine or thermostat on the 4.0 which is a lot (like 4 this year already) this happens for a few drive cycles.
The sensor is likely reading an air pocket and it moves because the air pocket moves over the sensor and then not

 

[donalds]

0hv 4.0?

Gauge was working before stat?

I lean more towards trapped air then a faulty t stat with the wild gauge fluctuations

Seriously, basically everytime I change an engine or thermostat on the 4.0 which is a lot (like 4 this year already) this happens for a few drive cycles.
The sensor is likely reading an air pocket and it moves because the air pocket moves over the sensor and then not

I'm sorry I assumed it would Have Been installed correctly

 

[Pete Deering]

I put a new thermostat in my Explorer. 190 degree or what ever the factory calls for.

The temp wanders now where as my other Explorer is rock steady and never moves.....same as my wife's car, rock steady.

I have Burped the coolant system...it never overheats.

Anyone one else have this issue?

The pictures below are the high and low movements.

View attachment 440533 View attachment 440534

That is cause By air trap in the upper manifold area. There is a TSB on it. I had the same problem. Hopefully you turn the weep hole on the new thermostat up.
The TSB adds a tee in the lower hose and circuLated coolant to the manifold where the temperature gauge sensor is located. I remove it.
To fix your issue you can either do one of two things.
1. Lift the front of the vehicle up in the air and Purge the radiator as the engine is running or; ( what also helps using a no-spill funnel)
2. Buy a coolant vacuum purge. What is does, it pull the coolant out as it pull a vacuum on the system. As the system is in a vacuum, you fill the system backup with coolant you remove or are adding, using the vacuum you created.

 

[Pete Deering]

That is cause By air trap in the upper manifold area. There is a TSB on it. I had the same problem. Hopefully you turn the weep hole on the new thermostat up.
The TSB adds a tee in the lower hose and circuLated coolant to the manifold where the temperature gauge sensor is located. I remove it.
To fix your issue you can either do one of two things.
1. Lift the front of the vehicle up in the air and Purge the radiator as the engine is running or;
2. Buy a coolant vacuum purge. What is does, it pull the coolant out as it pull a vacuum on the system. As the system is in a vacuum, you fill the system backup with coolant you remove or are adding, using the vacuum you created.

This Is just a example of one, I do not own this one.
View attachment 1680226651526.png

 

[dudemancool1904]

Not sure if it helps but I have a 5.0 that I did a coolant flush on and it exhibited the same symptom. Hooked up the obd2 scanner and confirmed the thermostat was opening at 192, it ended up being air just bleeding itself out of the system. Took a week or two of normal driving but it just worked itself out.

 

[410Fortune]

Yep just a few drive cycles and air bubble will burp

 

[Pete Deering]

This Is just a example of one, I do not own this one.
View attachment 440536

Here is the unit I have and the TSB

View attachment 440592 View attachment 440593

 

[C420sailor]

Mine does that when it’s very cold out and I turn on the heat

 

[G-Man53]

I put a new thermostat in my Explorer. 190 degree or what ever the factory calls for.

The temp wanders now where as my other Explorer is rock steady and never moves.....same as my wife's car, rock steady.

I have Burped the coolant system...it never overheats.

Anyone one else have this issue?

The pictures below are the high and low movements.

View attachment 440533 View attachment 440534

Sounds like a voltage problem. Check with voltmeter?

 

[Exploder321]

Some cars have idiot gauges, really an idiot light in gauge format. The needle goes to a preset location unless the sender indicates an out of range condition. My oil pressure gauge is like that. Maybe you now have a real temperature reading.

 

[Pete Deering]

Some cars have idiot gauges, really an idiot light in gauge format. The needle goes to a preset location unless the sender indicates an out of range condition. My oil pressure gauge is like that. Maybe you now have a real temperature reading.

The oil pressure Gauge uses a switch. On is 1/2 on the gauge and off is 0.
The coolant temperature gauge, uses a sensor.

 

[chuck1022]

Ineteresting...never new that with gauges.

Maybe I gotta take the wins where I can get them

All check engine lights are off
It is not everlasting

I will worry about it later

Bonus question

What are these on my explorer

 

[410Fortune]

Somebody added those some sort of mount for a gps a phone a tuner or???

 

[c96drumm]

Why did you replace the thermostat? Reason I ask is that once, many years ago, I replaced a good thermostat with a new one just because it was convenient to do so since I was changing radiator hoses. The new one was bad. Lesson learned. I never change a part without a good reason.

 

[chuck1022]

Why did you replace the thermostat? Reason I ask is that once, many years ago, I replaced a good thermostat with a new one just because it was convenient to do so since I was changing radiator hoses. The new one was bad. Lesson learned. I never change a part without a good reason.

My thermostat went bad....wouldn't open.


Maybe my nee one is wonky

 

[jr230]

It fluctuates the whole time you drive. Never gets hot. I do not remember the brand. It's a simple swap. I will put another one in.

try getting scanned at one of the part stores that offer free scan . not sure if they have dealer type that analyses all not just codes the basic ones do . but thermostats not too expensive replace it again. but if it defiantly not overheating you could ignore it\
but do check the connection at the sender if i remember its close to where you replace thermostat so connecter could be loose or corroded and not making good contact