Help Please OVER COOLING??

[frdracfan]

Well im new to this forum so I want to say hello first.
Second, I replaced my t-stat yesterday with the correct oem temp t-stat. Problem is while sitting still I see it reach the M on normal then the t-stat opens and it falls to N on normal. Everything looks fine. While on the way to work this morning with it being about 25 degrees F, it did ok only reaching the O in normal falling to below the N when it opened doing about 40 MPH. When I hit the interstate it fell all the way to cold while doing 70 MPH. I got off the interstate and it rose back up opening and closing between M and N.

I have heard of a stuck open t-stat going to cold on the interstate but it operates fine while sitting still.

What could be the problem?? The heat out of the heater was hot until i hit 70 then it was only luke warm at best.

 

[SkiTsO]

If it was working fine in the warmer weather it might not be closing all the way. You could put a piece of cardboard across part of the radiator and see if that helps in the cold weather.

 

[Convict1997]

The cardboard should work to warm it up but that would only be a band aid, not actually fix the problem. I'd start by removing the thermostat and put it in a pot of water on the stove. Put a thermometer in the water and turn the stove on. Check the temperature at which the thermostat opens and then take it out and make sure it closes all the way. That will be a start and let you know if the thermostat is working correctly.

 

[glfredrick]

I've often found that vehicles over-cool in cold weather. It is very normal for people in cold climates to use "winter fronts" and/or cardboard to block off a portion of the radiator to help with keeping the vehicle warm.

Typically, this problem only happens when temps get below zero.

If you are using cardboard, it is VERY important to allow air to pass through the center of the radiator with a belt-driven water pump and fan. If the fan has to suck against the cardboard, it will soon destroy the bearings in the water pump. Most of the time, a 12" to 14" hole in the center of the cardboard will be sufficient.

Make sure you remove the winter front when temps rise above freezing!

One additional item you might want to check is the fan clutch. Make sure that your fan is not spinning all the time. It should free-wheel or spin very slowly until the engine temps are moving toward high, especially on the freeway at 70 mph. Modern engine fans, unlike earlier vehicles, are designed to pull a TON of air through the radiator, and also to cycle on as needed (electric or belt-driven as is the Explorer). If they run all the time in cold weather you will likely never get the engine to properly warm up.

I'd also make sure that you have a 195 degree thermostat. Though OEM, there are different temperature ranges, and it is possible that you have a 180 or colder instead of the 195 you need. I've found that the Ford 4.0 (and 2.9) do not respond very well to cool engine temps unless they are seriously modified. Because the engine management system is designed (mapped into the computer) around a 195 temp setting, fuel curves, spark timing, cylinder pressures, etc., are all thrown off when running a cooler engine. With an add-on chip like a JET, etc., you can run cooler temps, as they are mapped for that. With a stock PCM, run the 195.

Hope this helps...

 

[frdracfan]

I did put a 198 degree t-stat in. The only reason I changed it was because it had 180 in it before and since it got colder I put in the 198. Yesterday it was about the same temp outside and with the 180 in it sould stay within the normal range and now that the 198 is in it goes to cold. wierd.

 

[frdracfan]

Ok found the problem....stupidity!!! I put the therm in backwards.....I know ...

 

[CDW6212R]

Good to know, that has happened to others before. If the thermostat is working properly, the cardboard trick should not be needed. The thermostat will keep the heat in the engine, not allowing anything but overheated water out. I have never needed to block my radiators. Regards,

 

[DeRocha]

Ok found the problem....stupidity!!! I put the therm in backwards.....I know ...

yeah... that would do it..

 

[glfredrick]

Good to know, that has happened to others before. If the thermostat is working properly, the cardboard trick should not be needed. The thermostat will keep the heat in the engine, not allowing anything but overheated water out. I have never needed to block my radiators. Regards,

Not to pick on you, but in Tennesee you would never need to block a radiator. Move up to northern Wisconsin or Minnesota and we'll talk again... Ever woke up to -35? Good luck even getting your vehicle to turn over, much less warm up. In those temps, diesel fuel is the consistency of Karo syrup, and everything else is worse.

 

[CDW6212R]

We've had -24 here, I installed my first radio in my car that night. We see cold, but not much snow lately. I have lived in Minnesota in Winter, my Mother has most of her family up there.

Cold weather helps cooling systems when they are up to temperature, but any engine will overheat if you don't have a radiator. Meaning that the thermostat is necessary to allow some coolant in/out to cool off going to/from the radiator. I am not suggesting you will overheat with the cardboard etc. But the cooling is needed, and with the thermostat working well, the engine should not run below the rated temperature. I'm not talking about running in -35 constant temperatures, but most vehicles that you see on our highways are not in temps that cold. I see trucks here constantly in Winter with the covers on the front.

I would suggest having the cooling system maintained as well as possible, and allow it to do its job. Regards,