I'm new to this forum, but did a lot of searching and have not found an answer to my 2000 Ford Ranger 3.0 AT problem.

The problem: My temperature guage does not move EVER and I get very little heat. I have gotten OBD trouble code P0125.

I have plenty of coolant. I have replaced the thermostat... twice. I have replaced the ECT sensor and the other temp sensor... twice.

Please help!

T

 

Welcome to FTE.

Well the P0125 says the computer agrees with your findings, that the engine is running cold.

Typically a stuck open thermotat, maybe a improperly installed thermostat, or seeing as how you've replaced it twice now, maybe a bad production lot, if you've bought both at the same place & they were the same brand, or maybe you bought the wrong heat range.

What brand & temp range did you buy & which way did you face the bimetallic spring on installation????

 

I bought a fail safe model and neither were stuck open when I un-installed them. I'm pretty sure the spring was on the engine side. It looked like there was a notch cut out for the other side that fit into the thermostat housing? Do you whether it could be the heater core? Should inlet and outlet both feel hot after 10-15 min?

Thank for the reply... much appreciated.

 

From what I understand, even if it's installed backwards or even removed, the engine should heat up to normal operating temp, it would just take it longer. My gauge doesn't move off the very bottom, which makes me think it's a gauge problem, since I've replaced everything else. Anyone know what controls the gauge for the temp that I could replace?

 

And you made certain you burped the system correctly? If your coolant has bubbles in it, it can adversely effect the readings. What brand thermostat did you use. I would strongly suspect that you have a bad radiator cap. Have you looked into that. If the radiator cap is bad, the pressure will bleed off, resulting in a drop in temperature.

 

Seems to me we have three things teling us that the engine isn't warming up.

You say you have little heat from the heater & this is verified by the engine temp gauge and the computers engine temperature sending unit telling the computer the engine is cold & to set the P0125 code.

How is your MPG???? It should be down if the engine isn't warming up, as the engine will likely remain in open loop operation

If the engine is fully warming up, the top radiator hose should be warm enough to be uncomfortable to touch, in 20 min or so.

If it's getting too hot to touch, then you likely have two or three other problems, like a bad gauge & engine temp sender ( unsual that both would go bad at the same time) & maybe a clogged heater core, or bad heater control assy.

The engine temp gauge is controlled by a temp sending unit, located close to where the top radiator hose connects to the engine. The sending units resistance drops, as the engines temp rises.
You could check the temp gauge, by removing the gauge temp senders wire & grounding it. This should cause the temp gauge to indicate full scale Hot.

Be careful & not confuse the temp gauge sending unit with the computers temp sensor, which is close by. The gauge sender has one wire going to it.

So what temp range thermostat did you buy???? Was it a Motorcraft thermostat???

The engine won't fully warm up with the thermostat removed. It's important to get the thermostat installed correctly.

 

Even with the thermostat completely out, the gauge will move off the bottom peg.

Something has to be going on. I agree with some of the other suggestions.

Feel your upper hose after it's been running a while. It should be warm to hot. As the stat opens up, you can feel liquid moving through it, if you squeeze it. ( Do this before it gets too hot!)

You can check your temp sensors for resistance. Go to autozone or get a manual and find the specs. I had heard that Ford eventually went to a single temp sensor, but I think that you should have 2. The one wire one is for your gauge. Measure between the connection and ground. It's also possible that one or both of your sensors have a bad wire or a loose connector.

If you have an air bubble in your system, you won't get heat, but typically the gauge reads HOT. This is because the air bubble usually keeps coolant from moving through your heater core, but it also keeps it from cooling your engine effectively. If you have this, your engine would seem awfully warm, even if your temp gauge said it was cold.

Your heater core could be plugged. This supposedly sometimes happens when
sand from the manufacturing process gets left inside andeventually gums things up.

Anyway, I think that you may have multiple problems. I'd start by trying to find out if your engine is really warming up. Then you might consider checking some of the other areas to see what's going on. I didn't note where you were, but it's just not cold enough for the temp gauge to stay on the peg!

good luck,

ford2go

 

I don't know if it was mis-wording between posts, but he replied that he put the SPRING toward the engine.

*"I'm pretty sure the spring was on the engine side."

When the term "bi-metallic spring" was used ("What brand & temp range did you buy & which way did you face the bimetallic spring on installation????"), it was more indicating the copper looking slug, or chunk of metal. That should be toward the engine. The more visible spring is the spring that closes the thermostat. This should be away from the engine when installing.

I think maybe just a bit of clarification could help us here.

 

Id agree that the thermostat is bad. If the temp gauge isnt coming up into the normal range and you arent getting heat out of the vents, the engine isnt warming up.

 

The one thing I have not seen is whether your fan ever cuts off. My 1993 Ranger has a low temperature/no heat problem, but my fan NEVER shuts off...runs All the time...Have you ensured your fan intermittently cuts on and off??

 

You've given me some good tips. I will verify the heat from the top and bottom radiator hoses. Can anyone tell me for sure whether the spring side of the thermostat should be toward the engine or toward the hose? I would think that if it's the spring side moves the valve once it heats up, it would need to be on the engine side, which I've done. Any ideas on troubleshooting the heater core? That seems like the next logical step.

 

Yes the big spring that you can see on the thermostat, goes toward the engine.

Also make sure that the Motorcraft thermostats air relief valve is in the up/12:00 oclock position. This will help in burping entrapped air from the cooling system.

The heater core isn't causing your engines low operating temperature, so for now concentrate on troubleshooting your engines low operating temp & get it put right & the computers low temp trouble code P0125 & low heater ouput & low reading engine temp gauge, will likely be solved.

Once the engine is detemined to be at the proper operating temp, if the heater still has low ouput problems, shut the engine down, let it cool & pull it's inlet & outlet hoses & try a reverse flow flush, with your garden hose & some spare heater line & see if it's clogged up. Sometimes a reverse flow will dislodge a blockage. Remember though, this is a 16 lb pressure system, so go easy on the water pressure, so you don't pop the heater core & make a mess inside the cab!!!!

What temp range thermostat have you installed?????
Have you noticed a drop in MPG since this problem came up????

 

Interesting! There are about a thousand reasons that a vehicle will overheat, but very few reasons it won't heat up, and 99% of the time it's because the coolant flow isn't being throttled by the thermostat. If this is the case, you should be able to see/feel coolant circulating through the radiator when the truck is completely cold.

 

This is really puzzling!!! I replaced the thermostat with a Fail Safe model thermostat from Autozone. The Ranger heated to normal once; then it only got about half way there after a week. I assumed it had failed in the open position and was a bad thermostat, so I exchanged it, even though visually it did not fail in the open position. After I put the new Fail Safe thermostat in, it did the same thing. And YES the gas mileage has been getting pretty low. 15-16 MPG.

The fan runs all the time... but the A/C clutch kicks on and off... nothing abnormal.

I assumed this whole time that the engine was heating up and it was some type of sensor. So I checked today... the hoses are all warm, but not hot. AND after driving the thing in the city and on the hwy for 30 min in 50-60 degree weather. I open the hood AND PUT MY HAND ON THE RADIATOR CAP AND IT'S NOT THE LEAST BIT HOT????? How can this be? The heat from the engine has to be dissipating somewhere?

The reservoir is half full. There is coolant in the radiator to the top. When I replaced the temp sensors, there was coolant in there as well. I have a hard time believing that this will all be fixed by getting a Motorcraft thermostat. Let me know.

 

Well seeing as how you've pretty much confirmed, with the touch test, mpg drop, low temp gauge reading, computer code P0125 engine not up to opeating temp & heater not putting out much heat, that the engine isn't warming up & seeing as how you've used two AZ thermostats, I'd say maybe they have a faulty production run as I guessed earlier.

SO, I don't think I'd likely try another AZ thermostat. BTW what temp range thermostat did you install????

Why not use a Motorcraft thermostat, it's designed for your Ford, with a air bleed valve, that sure makes it easier to burp the system.