Hi,

I'm hoping someone else has had this issue:

My '00 Ranger, 3 lt flexfuel, has 172K miles on it. The water pump finally gave up and I had to replace it. After getting the entire front of the engine "decluttered" the old pump came off without a hitch. The new one went right back on. After reassembling the thing it turned out the the nipple on the elbow, that also is the mounting postion of the temperature sensor, was also leaking. Again the whole thing comes apart. I was lucky in that the local Ford dealer had the elbow in stock (for only $26) but not the sensor, which broke upon removal. I went to NAPA and got the sensor and a new lower hose, which has the bypass the goes up to the elbow. I got it all back together, again, and all is well except the gauge on the dash reads colder as the engine warms. Any suggestions?

 

If what you are referring to has 1 wire connected it is a sender, not sensor.

Fuel injected engines have 2 coolant temp readers.

The ECT(engine coolant temp) sensor has 2 wires and is connected only to the computer, the computer uses this sensor to run engine rich with a high idle when cold, as sensor warms up idle slowly drops and fuel mix gets leaner.

Coolant temp sender has 1 wire, it is only connected to the dash board temp gauge.

These look similar but are not the same, so are not interchangeable.

Because these are both Engine Coolant Temp(ECT) readers it can be confusing for the DIYer AND the auto parts guy who is looking it up, lol.
Easiest thing is to look at what they bring to counter, if it has 1 wire connection it is the Sender for gauge, if 2 wire connections then it is the Sensor for the computer.

I don't have a 3.0l so don't know which one is on the elbow

 

Here's a picture from a 3.0 to help. The lower left has the single wire, and is the coolant sender for the cluster gauge. The one to the right has the two wires, and is the coolant sensor for the PCM:

 

Ok, thanks for that, but your reply doesn't really help me figure out WHY it worked before I replaced the water pump and doesn't work with a new sensor now.

 

"Because these are both Engine Coolant Temp(ECT) readers it can be confusing for the DIYer AND the auto parts guy who is looking it up, lol."

You have the wrong sender

 

Another possibility if you did install the correct sender: did you use teflon tape on the threads? If so, you only want this tape on the upper part of the threads, as the sender itself needs to make a good ground. It is the function of the sender to provide a variable ground for the cluster gauge to work.

Do this: remove the wire that connects to this sender you replaced. Turn the key to "on", don't start the engine. Ground this wire. Did the gauge needle move? If so, the wiring and gauge are good, and the sender is bad, or its threads are not making a good contact to metal.

Thanks to RonD for providing this test to me awhile back. He's the Ranger man. I swear if he ever runs for any political office, I will move there, and vote for him.

 

Thanks, now that I can use. Soon it warms up a bit, I'll try that.

 

Hmm? Question.. My ranger temp rises as I accelerate . Then I let off throttle, it slowly falls back in middle , normal range.. Do I replace Pump? Fan clutch? Or thermost. Fluid is great, no visual leaks, all that said, I crank truck open rad cap, rev engine I do notice fluid circulating , I'm stumped on this one.. Please help. Thanks

 

I take it the oil pressure gauge doesn't also go up with RPMs?

Reason I ask that both are electrical and would do that if Alternator was going out.
i.e. battery voltage at idle(12.5v) then 14v above idle.

Normal failure of fan clutch is when engine temp rises at idle then goes back down when driving, so opposite of what you see.

An Engine, of course, generates much more heat under load, so accelerating would cause rise in head temp, the flow of the coolant thru the heads needs to increase at this time which is why an RPM matched water pump is used, it increases flow with RPM increase since it runs at crankshaft RPMs.
So your issue reads like a circulation issue, or more a lack of circulation issue.

So your guess about the water pump would be a good one, its impeller blades can get eaten away by electrolysis reducing the flow volume so at idle there is enough circulation but not enough under load even with higher spin RPMs.

But a 1/2 open thermostat or clogged radiator will act the same, it allows flow but not full flow.
You can test for this by leaving rad cap off and warming up the engine until thermostat opens.
Leave cap off and have someone rev the engine to about 2,000rpms and hold it there, if coolant starts to come out the rad cap opening then I would suspect rad is getting clogged up, water pump will pull in coolant from lower hose at the same rate it is pushing it out of the upper hose so no coolant should come out the rad cap opening.
You can also feel the rad after it is warmed up, shut off engine, loosen fan shroud and move it back, run you hand over the rad fins, there shouldn't be any colder spots, you should feel nice even heat all over, a colder area means a clogged spot.

Put cap back on and rev engine again, squeeze the upper and lower radiator hoses, if lower hose is getting much softer than upper hose then rad could be the issue, coolant is being pulled out by the water pump faster than it can be replaced, this could also point to thermostat not being open all the way, it limits flow to upper rad hose.

If both hoses feel the same then I would suspect water pump, its flow is equally poor on both hoses.


There is also the by-pass system used when engine is not using the rad, during warm up.
I assume the heater works fine, that is part of the by-pass system.
Generally if by-pass system has a clogged valve/hose you would see more random heat up/cool down cycles, but it could match RPM.
But if heater is working normally, hot heat, I would take this off the table.

 

Hey, Mr dean.... Thank you for reply.. A lot of good info, I plan to jump on this as soon as weather here gets a little warmer... Thanks again Sir...

 

I just had a problem with my tempature gauge not working correctly and my heater was only lukewarm on my 2000 ford ranger 4.0l. The problem was my thermostat not working being open all the time, letting radiator coolant to enter the engine always. The engine never warmed to 195 degrees because of this. Also, I replaced the coolant temp sender (one wire for dash gauge) and the coolant temp sensor (2 wire for PCM). They almost look identical except thehere are 3 tabs on the units and the one in the middle for the sender tab is offset a little so the sensor connector won't fit. That's how you can tell sender from sensor. Sensor tab is straight in the middle. Even though the sender is only 1 wire, the actual sender will still have 2 flat pins in it.

 

I’ve done all that as far as fuel filters and the light however are the CTS is not something that I had thought of. How do you check of six years anyway, replace with a new one? Checked throttlebody it does not appear to have any wear issues and I doubt that a screw weighing 2 grams or less would effect it. The surge is only 100 RPM or so up-and-down for couple or three times.
thanks, Larry

 

This was what was installed in the truck when I got it. This was connected to the single wire harness not the double. The auto parts store does not have one


with just 1 wire connection in the coupling.

 

Welcome to the forum

Always good to post the year of the Ranger and the engine model
Your profile says 2000 4.0l?

Yes, around 1998 or so Ford started using 2 wire Temp Senders
Other wire was a Ground, red/white wire still went to dash temp gauge, if you short that to ground and turn on the key the Temp gauge should go up to HOT, if so that wire and the gauge are OK

The older 2 wire units also Grounded thru the threads of the sender but not all the new ones do
You can use an OHM meter to test it, metal threads to one of the "prongs" should show 0 ohms, the other prong HIGH ohms, if not then you will need to get another sender that does ground thru the threads or ADD a ground wire to your connector

Or you can use an older 1 wire temp sender and change your connector to match it, usually a stud/nut terminal, so crimp an eyelet on the end of the red/white wire

 

Thank You RonB! This was my first post so excuse the omissions. I have a Ford Ranger XLT 2000 4.0 V6

I replaced the cone shaped sensor to the right as seen in the picture and the plunger shaped sensor on the left. The ODBII reader shows the water temperature only reaches 150 when its warmed up. The heater works great and the dash gauge never gets any higher than than indicated in the picture. I did the test on the sender wire to ground and the gauge tested good going all the way to hot. Does this mean I have the wrong sender? I appreciate your help.

 

I did ohm the two prongs on the left sensor shown in the picture from my post and one prong was 0.2 and the other was 274.0

 

Yes, the red connector is the sender for the dash temp gauge

You will need to replace the thermostat at some point, ECT(OBD2) temp should be 175-185degF, after 5 to 8min warm up
Use a 190deg to 195deg thermostat

You ohm'ed it to the metal threads?
If so thats OK readings
The 0.2 ohm prong is the Ground, red/white wire should be connected to the other prong, but 274 seems way to high

Not sure if Ford ever change the Sender ohms, but in the "old days" these were what to expect: https://www.vintage-mustang.com/atta...14-png.761171/

 

You are the man! I appreciate it. I think the ohms were higher because the engine was still a little warm, if that makes a difference? I will order one today.

 

Hello I have an 2004 ford ranger 2.3 4l. My temperature gauge needle moves slowly over a few minutes to above c at then falls below c after about 8 miles drive

replaced CHT problem remains.

Going to replace the SENDER next. I’m checking to confirm that the sender is still in the same location as talked about in the forum at the rear of the engine between the firewall and the engine with a total of 4 wires going into it. (2 ea 1 color possibly white or red, 2 black.)

Im also wondering If my issue could be anything else?

 

Welcome to the forum

Yes, up thru 2006 Rangers still used a Temp Sender for dash board temp gauge
Yes, on the 2.3l DOHC Duratec 2001-2006 temp sender is behind the head on a metal coolant line, so between head and firewall, red/white and black/white wires

CHT is only used by computer in 2001-2006 2.3l Ranger

Could be thermostat starting to fail
On the 2.3l the thermostat is on the lower radiator hose at engine end
It should partially open when coolant temp in lower engine gets to 170degF(its rated at 180degF), upper engine coolant should be 185-195degF at that time, it should show just below 1/2 on the dash temp gauge
If the thermostat is opening all the way at say 140degF then temp gauge would drop, back to C when the cold radiator coolant rushed in
BUT........after a few minutes temp gauge should start to go back up a bit, but would not reach full warm up temp, just below 1/2, maybe back up to 1/3

Faulty sender probably wouldn't come back up after the drop
But its all guess work, heck, it could be a faulty gauge, but hope not

Also simpler test is to check your heater air temp
Have heat temp on HOT, fan on
Feel the air as temp warms up
When temp gauge shows the DROP feel if the air temp is also dropping, if so then the temp drop reported on gauge is REAL, so most likely thermostat
If air temp doesn't drop then false temp reading on gauge, so sender issue

 

Ron,
thanks for your input and prompt response. This foum has been extremely helpful. This seems like it might be a SENDER issue because heater blows hot and no Change in temperature. The gauge moves but doesn’t display correctly. So hopefully the sender is failing and replacing it will fix the issue. If not I’ll check the thermostat and cross my fingers.