Need some help here.

I have a 2000 Excursion. With 125k miles on it that I drove here to washington state from Los Angeles with my family for Christmas.

A few days ago, my OBD program reader picked up an error code "P1025"- which is "insufficient coolant temp" error code.

Through some online research on these forums, I deducted that it must be a thermostat stuck open causing this.. reasons were that the heating air temp never go nice and hot as a V8 should push, and the coolant temp never got above 110 degrees.

Local ford dealer had a new thermostat, picked it up, installed..done.

However, after the fact, my heater was blowing hot then cold air every 5 or so minutes. So after some more research, a phone call to a local mechanic, it seemed to be air In the system. Mechanic told me to take the truck for a long drive to bleed it out so I oblidged.

Took a drive up to the mountains and enjoyed beautiful hot air on the way up so problem fixed right.?

Stopped for an hour for lunch, and when we got back In to go, the truck immediately overheated up to 250 degrees, the failsafe system kicked in, so I pulled over and let it cool down. Took off again, overheated again and pulled over for a longer period of time then took off hoping for the best.

Watching my OBD coolant temp monitor closely, the thermostat started to work correctly. After hitting 199.4 degrees, the thermostat would open, and the coolant temp would drop down to about 179, then cycle back up again and so on.

To me, I assumed it was a stuck thermostat because of the cold, or maybe an issue because it was new.

The aor temp. been consistently in the high 20s to low 30s here I may add.

Our of concern, I started the truck up this morning so that I could make sure everything was still good, but unfortunately the overheating issue arose again, and the it doesn't seem to be correcting itself.

So, from my limited technical experience, I have made the following assumptions:

- the replacement thermostat is bad, so maybe I should reinstall the old thermostat so I can get it to the dealership.

Anyone else have any feedback?

There is no coolant leaking on the passenger floorboard

There is no leak on the waterpump that I can see

I also find it weird that my temp gauge on the dash was not even registering the actual temperature of the coolant as it was below the 1/4 mark on ch while my OBD monitor was showing 240 degrees.

Needless to say, we need to head back home Tuesday. .

Help please!

 

A safe quick fix for the drive home would be to pull the thermostat completely until you get home. Obviously the motor probably won't get to full operating temp, but in order to get back without any other issues, that's what I would do. Because the thermostat and gasket won't be in there, you may notice a slight coolant leak coming from there, but nothing to be concerned over. Just make sure to burp the system and fill the overflow tank.

Or, run to an autozone and buy a new one, w/new gasket.

 

Well while it could be a bad thermostat it could also be a blown head gasket. Sorry to drop that on you but if it is a bad head gasket you can hydrolock a cyl with coolant and pretty much damage your engine beyond repair. Take it to a mechanic or radiator shop and tell them you need a hydrocarbon test on the cooling system. If you have hydrocarbons (combustion chamber gases)in your coolant its a safe bet that you have a blown head gasket which must be replaced before you drive much more. A spike in coolant system temps can be from a bubble of super hot combustion gases traveling through the system eventually passing by your cooling temp sensor. The gases get into the cooling system when a head gasket is compromised and the high pressure gases in the chamber is forced into the cooling system via the head gasket defective seal. FYI a compression test will not always give you a positive test for a blown head gasket. Good luck.

 

Just a heads up guys..

I took out the "new" thermostat and replaced it with the old and the overheating problem is solved.

However, the old thermostat never let's the engine get above 127 degrees, and the heater does not get nice and hot... which tells me that the replacement thermostat is the issue.

I also think it may be due to the fact that the previous owner may have had it programmd-chipped tuned for southern california, and that may be the biggest issue because of the climate difference.

 

Sounds to me you just have 2 bad thermostats. Try a third one.

 

I hope you are right but my experience tells me this problem is not resolved...time will tell.