Correct Thermostat Temperature -- 4.0 OHV

[96eb96]

Needle stays at bottom line normal range or a little below

If it says at the low C line, then you should change the stat.

 

[mhanglow]

Ok

 

[lobo411]

How much does it drop?

When it's warming up, it'll rise to about the upper edge of the gauge's "thermometer" image. Then it drops down to the lower edge of the thermometer, and rises to about the middle of it.

 

[Steven Arredondo]

Anyone know what the correct thermostat temperature should be for a 1996 4.0 OHV? My engine has been running cool ever since I installed an Autozone 198 thermostat last summer. The gauge used to get right between C and H and stay there, but now it gets to the low 1/3 and stays there.

I'm going to check the exact temperature using my scan tool today, but there seem to be a ton of different thermostat temps listed as "correct:"

Haynes Manual: 192-199 F
Autozone: 198 F
Rockauto: 195 F (OE Temp)
Rockauto: 198 F (OEM Recommended Temp)
Fordparts.com: 197 F

Just an average Joe who believes the oem temp for the thermostat only needs to be considered if you live up north. Installed a 174 here in Florida and it's perfect. Running a high temp thermostat down south and an emergency arises you don't have much time before that temp can touch 220-230. At that point you're sharing stories on the forum page about head gasket failure.

 

[239]

Just an average Joe who believes the oem temp for the thermostat only needs to be considered if you live up north. Installed a 174 here in Florida and it's perfect. Running a high temp thermostat down south and an emergency arises you don't have much time before that temp can touch 220-230. At that point you're sharing stories on the forum page about head gasket failure.

I’m in Florida too and running a 190. I might switch to a lower temperature.

 

[AeroRamer]

I am in north Florida. My 2000 4.0 SOHC runs between 180-185. I have a 185 thermostat.

 

[239]

I am in north Florida. My 2000 4.0 SOHC runs between 180-185. I have a 185 thermostat.

I’ve been thinking about going to a lower temp, but it seems that the spark plugs and other ignition systems work best at 190, from what I’ve read.

 

[AeroRamer]

I’ve been thinking about going to a lower temp, but it seems that the spark plugs and other ignition systems work best at 190, from what I’ve read.

Hmmm. Interesting. I've have not heard of that before. Not that I am changing it again (one PITA screw) but what about it make it better? I am curious.

 

[bluestream1]

I am running a RT-1160 in my SOHC and the temp hangs right near 181F on scan tool with 50F outside temps. However, Its now 10 years old

 

[mhanglow]

I have also read, the reason temp gauge stays in the low scale or bounces a lot, is because the temp gauge sender unit is grounded to the engine block. Corrosion could cause bad ground and erratic temp gauge on dashboard.

 

[239]

I have also read, the reason temp gauge stays in the low scale or bounces a lot, is because the temp gauge sender unit is grounded to the engine block. Corrosion could cause bad ground and erratic temp gauge on dashboard.

Mine would tend to stay in the lower 1/3 of the scale. I replaced it even though it wasn’t throwing a code and it’s much more accurate now. Especially when I check the coolant temperature with my Blue Driver scanner. At almost 20 years old, it was time to replace it. I also changed the ecu coolant sensor.

 

[239]

Hmmm. Interesting. I've have not heard of that before. Not that I am changing it again (one PITA screw) but what about it make it better? I am curious.

I’ll have to look for the info again. But I’m assuming that’s just the coolant temperature that the components were designed for.

 

[239]

I am in north Florida. My 2000 4.0 SOHC runs between 180-185. I have a 185 thermostat.

My 190 thermostat never allows the coolant to go above 185. Isn’t is supposed to open and stay open at 190? I’m getting pressure in the coolant system when the truck is cold, even after new heads and head gaskets. So I know it’s not exhaust in the system at this point. I wonder if the thermostat is causing this build up.

 

[AeroRamer]

My 190 thermostat never allows the coolant to go above 185. Isn’t is supposed to open and stay open at 190? I’m getting pressure in the coolant system when the truck is cold, even after new heads and head gaskets. So I know it’s not exhaust in the system at this point. I wonder if the thermostat is causing this build up.

I think that is how it is supposed to work. I do not know why it will be opening at 185. It could be that it is within its tolerance range.

 

[239]

I think that is how it is supposed to work. I do not know why it will be opening at 185. It could be that it is within its tolerance range.

I think mine may be stuck open. It gets as low as 170 lately. I’ll be replacing it with a 195 Stant superstat.

 

[96eb96]

My dash gauge is accurate and reflects the scan tool very well. I tried the motorcraft and now I have a stant superstat.

I move around between 172-188 according to the scan tool. There were tsbs for this engine about steam formation and a bypass tube (which is long gone). It went from the lower radiator hose to an adapter on the sender. I'm also convinced if you see fluctuation you probably have microscopic head cracks pushing steam into the system and making the gauges read lower.

 

[239]

My dash gauge is accurate and reflects the scan tool very well. I tried the motorcraft and now I have a stant superstat.

I move around between 172-188 according to the scan tool. There were tsbs for this engine about steam formation and a bypass tube (which is long gone). It went from the lower radiator hose to an adapter on the sender. I'm also convinced if you see fluctuation you probably have microscopic head cracks pushing steam into the system and making the gauges read lower.

Unless king cylinder heads sent me defective units, then I doubt I have exhaust gas in the coolant. I suspect the bleed hole may be clogged on my old thermostat. I’ll know for sure when I pull it in a few weeks.

 

[96eb96]

Unless king cylinder heads sent me defective units, then I doubt I have exhaust gas in the coolant. I suspect the bleed hole may be clogged on my old thermostat. I’ll know for sure when I pull it in a few weeks.

Quite unlikley, but take your cap off and see if it rises when it runs. Also the glove test. I heard one solution is a Tee in each heater hose, and joining them. I never tried it. I know there was definitely a special lower radiator hose that ran a branch to the coolant sender. I almost bought it but the ford parts guy said it is a waste and won't make a bit of difference for performance. He had 4.0 OHV ranger with 300K, he said the sender moves, so what. His opinion was that the explorers have a massive heavy duty radiator, so that cools things down fast.

My stant T-stat has no bleed hole, but is supposed to have a tiny vent machined in.

 

[0scarsky]

Well, I'm not sure what did it, but now my dash gauge operating temperature is back to normal. It's also displaying more "normal" behavior--IE, before the engine was getting to the low 1/3 on the gauge that was about it. Now it gets up to the 1/2 point, and then I see a decent drop as the thermostat opens, and then it comes back up.

I changed the lower intake manifold gasket, replaced the thermostat, flushed the radiator (had a minor but still worrysome amount of brown sludge), and refilled. I don't know which of those might have done the trick, but I'm happy with the outcome!

Hello, what creates the brown sludge? I have a lot in my hoses and cooling system. Thank you.

 

[Josh P]

Hello, what creates the brown sludge? I have a lot in my hoses and cooling system. Thank you.

Not changing the coolant at the proper intervals will allow the engine block to rust from the inside. Another possibility is a bad head gasket allowing oil to mix with the coolant.