P0128 and grille cover for cold weather? | Ford Explorer Forums - Serious Explorations

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P0128 and grille cover for cold weather?

ARC95

Member
Joined
July 16, 2023
Messages
21
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20
City, State
WI
Year, Model & Trim Level
2010 Ford 4.0L SOHC Sport
Gentlemen and Ladies hello again!

I have a question for all you knowledgable folks. Driving back home yesterday night it was around just below 40 degrees F and after driving for about 10-15 mins I had my check engine light come on. I pulled over to the side of the road and plugged in my bluetooth code reader/live feed and saw that I had a P0128 code. I checked the coolant and I'd say it was a bit low so I added some to be safe. The temp gauge was not where it normally was, it was showing none of the graphic for coolant temp below the needle. When running normally you'd see it peaking out just a bit. I'll add I have a 2010 explorer with the 4.0 and about 1000 miles ago I changed out the radiator, therm housing and thermostat, water pump etc., basically the whole rad system. Could the p0128 have been from the slightly low coolant level? I check it periodically and it's been consistent before this. The p0128 is the code for engine coolant not being to temp aka being too cold. I drove the remaining 30 mins home after filling it with a bit more coolant and the temp was pegged right around 180, 183 at the hottest. As I live in Wisconsin, it's only going to get colder from here. Should I get a grille cover so all that cold air isn't blowing into the radiator and keeping it so cold? I'll be able to monitor the live temp so I'm not worried about overheating, just don't wanna keep the old girl too cold either :) Anyone from colder climates experience something similar and have advice? Also for the coolant being low, I need to replace the hose going from the radiator to the overflow tank, the one on now is original and when I swapped the rad it was a bit loose. I put a worm driven hose clamp on it but it's such a tiny darn hose that I think it leaks a SMIDGE of coolant. Like i see a few dried drops ever few days when I check. Any help is appreciated!
 



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At only 40F, a grill cover isn't needed. I've never needed one for my '98's 4.0L SOHC, though I've seldom driven it below about 15F as it doesn't get much colder around here, except before dawn.

Odds are it was just low coolant and will go away, or an air pocket trapped in the system if it persists.

Stuck open thermostat is another possibility but you recently changed that, and drove long enough that it should have gotten up to temperature either way. Even so, you could use a scan tool to check the engine temperature, and compare to the top radiator hose. Radiator hose shouldn't be getting firm and hot until the thermostat trip temperature is reached.

Until you replace the leaking hose, you could try adding a wire tie in addition to the clamp.
 
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180 is too cold for engine that's why the code is getting set. how the code gets set is when you start the engine a timer starts and if the computer doesnt see a set coolant temp before the timer runs out it will set the p0128 code.

are you sure you put in the same temp thermostat as stock? i belive it's a 190 degree thermostat that is stock. just because you recently replaced the thermostat it could be bad and that is not uncommon.
 






At only 40F, a grill cover isn't needed. I've never needed one for my '98's 4.0L SOHC, though I've seldom driven it below about 15F as it doesn't get much colder around here, except before dawn.

Odds are it was just low coolant and will go away, or an air pocket trapped in the system if it persists.

Stuck open thermostat is another possibility but you recently changed that, and drove long enough that it should have gotten up to temperature either way. Even so, you could use a scan tool to check the engine temperature, and compare to the top radiator hose. Radiator hose shouldn't be getting firm and hot until the thermostat trip temperature is reached.

Until you replace the leaking hose, you could try adding a wire tie in addition to the clamp.
For the grille cover it would be when it gets below freezing, Wisconsin can get to below zero often in a year. I agree it could have been low coolant level, I topped it off to the Cold fill line this morning and will monitor it this week. I'm also ordering new proper hose clamps, not really seeing just a hose for sale, I'd either need to get the same size and cut it myself or order a whole reservoir.
180 is too cold for engine that's why the code is getting set. how the code gets set is when you start the engine a timer starts and if the computer doesnt see a set coolant temp before the timer runs out it will set the p0128 code.

are you sure you put in the same temp thermostat as stock? i belive it's a 190 degree thermostat that is stock. just because you recently replaced the thermostat it could be bad and that is not uncommon.
I got a 2L2Z-8575-AA OEM thermostat and installed it into an aluminum therm housing by Simmons. It's ran fine in the hot weather, no overheating and engine temps were fine. It just popped up now with the cold weather.

I have a feeling it's from the coolant level being a bit low and with the cold weather maybe caused it to come on. I'll look into grille covers and be proactive so it can be at proper temps going forward :)
 






i hope it is just from low coolant but i dont think it is. the symptoms are exactly what i had happen with my 2010 4.0l it was fine in the summer and as soon as it got to 40°f outside same code. a stuck open thermostat was the issue. i have also had zero issues with my vehicle warming up correctly with temps in the -20 to -30 range but that was winter of 2014-2015 because it rarely goes that far below 0 here where i am in michigan.
 






+ or -40f?


If it’s plus 40 that’s jeans and a T shirt weather, for the truck you should actually better slightly performance than what you’d see at 72f

I don’t do winterzation kits on anything until it’s steady in the +19f and below range
 






i hope it is just from low coolant but i dont think it is. the symptoms are exactly what i had happen with my 2010 4.0l it was fine in the summer and as soon as it got to 40°f outside same code. a stuck open thermostat was the issue. i have also had zero issues with my vehicle warming up correctly with temps in the -20 to -30 range but that was winter of 2014-2015 because it rarely goes that far below 0 here where i am in michigan.
So you think it'd be a stuck open thermostat? The OEM should be a 190 degree thermostat. Ironic that after fixing my radiator to stop the engine from getting to hot I now have to fix it from staying too cold -.- Could I have messed something up when installing it and that's why it's stuck open or are these just notorious for being kinda crappy?
 






It's most likely you just had air in the system due to the prior work done, and it's bleeding off, so the coolant was low.

You're able to read the temperature, so just check to see if the radiator hose is hot.

In cold weather, if it drops, the thermostat should close. There is no need for a grille cover due to that, until it gets very, very cold.

If you want to pull the thermostat and test it, or replace, do that, but as mentioned this can be tested without pulling the thermostat.
 
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+ or -40f?


If it’s plus 40 that’s jeans and a T shirt weather, for the truck you should actually better slightly performance than what you’d see at 72f

I don’t do winterzation kits on anything until it’s steady in the +19f and below range
if you look my post i specificly put the negitive sign when i was talking about negitive temperatures so yes it was positive 40°f.
So you think it'd be a stuck open thermostat? The OEM should be a 190 degree thermostat. Ironic that after fixing my radiator to stop the engine from getting to hot I now have to fix it from staying too cold -.- Could I have messed something up when installing it and that's why it's stuck open or are these just notorious for being kinda crappy?
no, i am not saying its is a stuck open thermostat but don't rule it out just because its "new". i have replaced 4 thermostats in my truck and the one that was stuck open was only a year and a half old. do what J_C mentioned above you can also clear the code and see if it comes back if it does then you need to diagnose more. if you can read live data of the engine coolant you can check if its a stuck open thermostat by starting with a cold engine heat off and the engine should get to above 170°f within 5 or so miles of driving at 45mph. it should also get to 190°f and stay around there and not drop more the a couple degrees below.
 






So you think it'd be a stuck open thermostat? The OEM should be a 190 degree thermostat. Ironic that after fixing my radiator to stop the engine from getting to hot I now have to fix it from staying too cold -.- Could I have messed something up when installing it and that's why it's stuck open or are these just notorious for being kinda crappy?
There could have just been air left in the system due to the prior work done. Some thermostats have a little check valve, or people drill a tiny hole in the block plate, to help the system bleed the air out. A forum search should detail ways to bleed air out.

The OEM thermostats are not known to be crappy/poor-quality, nor are these vehicles known to have any related issues at temperatures of 0F and lower still. This is not an Explorer vehicle design or parts related, unique issue.
 






if you look my post i specificly put the negitive sign when i was talking about negitive temperatures so yes it was positive 40°f.

no, i am not saying its is a stuck open thermostat but don't rule it out just because its "new". i have replaced 4 thermostats in my truck and the one that was stuck open was only a year and a half old. do what J_C mentioned above you can also clear the code and see if it comes back if it does then you need to diagnose more. if you can read live data of the engine coolant you can check if its a stuck open thermostat by starting with a cold engine heat off and the engine should get to above 170°f within 5 or so miles of driving at 45mph. it should also get to 190°f and stay around there and not drop more the a couple degrees below.
Alright, I'll drive it some these next few days and see what my temps are. My reader also saves the live data and puts it in a spreadsheet which is nice.
There could have just been air left in the system due to the prior work done. Some thermostats have a little check valve, or people drill a tiny hole in the block plate, to help the system bleed the air out. A forum search should detail ways to bleed air out.

The OEM thermostats are not known to be crappy/poor-quality, nor are these vehicles known to have any related issues at temperatures of 0F and lower still. This is not an Explorer vehicle design or parts related, unique issue.
The thermostat I installed had a hole in it. I think some air got in from the coolant being low from a slow leak in the overflow tank hose like I said before. Worst case I can order another one, and put this one in the oven to see if it pops open when it's supposed to or not. I can also idle and burp the air out if it keeps happening.

I'll let you guys know what it was/what works or if I have any other questions :) thanks for the replies so far!
 






Alright, I'll drive it some these next few days and see what my temps are. My reader also saves the live data and puts it in a spreadsheet which is nice.

The thermostat I installed had a hole in it. I think some air got in from the coolant being low from a slow leak in the overflow tank hose like I said before. Worst case I can order another one, and put this one in the oven to see if it pops open when it's supposed to or not. I can also idle and burp the air out if it keeps happening.

I'll let you guys know what it was/what works or if I have any other questions :) thanks for the replies so far!
Blown head gasket. Got chocolate milk when I checked this morning under the oil cap after noticing coolant being low again. How hard is it to do a head gasket or is it recommended to take it in somewhere?
 






Is the only evidence you have, brown scuzz under (inside?) the oil cap? That can happen due to moisture accumulation without a head gasket problem. Is it also on the dipstick or found when draining the oil?

It's not a hard job to replace the head gasket(s) but does require understanding of what you're doing and taking a lot off to get to it. You might watch some youtube videos to see if it is within your wheelhouse. This example was found searching 4.0L SOHC head gasket, there may be some more Explorer or Ranger specific.


 






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