I am usually pretty good at diagnosing problems, but this one has got me stumped.
I have a 97 Ranger 2.3 standard shift, No A/C, a pretty simple Ranger with 158,000 miles. About a month ago while do some checking around under the hood I noticed my coolant overflow tank was empty, so I filled it up to the proper level with some anti-freeze mixture. Thinking if the system was low on anti-freeze it would suck what it needed from the recovery tank, wrong! About two weeks ago I noticed that my temperature gauge was NOT registering in its normal position and was considerably lower towards the Cold mark. Heat coming out of the heater was normal. I opened the radiator cap and everything looked okay. After a few days this would not go away and replaced the thermostat thinking the thermostat was stuck in the open position, wrong again! I burped the system by letting the engine run with the radiator cap off and filled the radiator with anti-freeze mixture everytime some of the air was expelled. I did this for a few days and noticed that the engine would not reach normal operating temperature at idle speed! I had to put something on the gas pedal to increase idle speed so the engine would get hot, this is not normal. Finally I got to a point where the radiator would not take anymore anti-freeze mixture, but the problem still exists.
Two things I noticed that will get the engine temperature up to normal, engine speed (RPM's) and not having the heater on. Let me explain, at normal idle the engine will not reach its proper tempature, but when driving down the highway the temperature goes up to normal (about halfway on the scale) no matter if the heat is on or not. When stopped at a light or just idling I can watch the gauge slowly go down towards the cold mark, if I turn off the heater it takes longer to go down to cold. I do know the heater fan is cooling the coolant to a degree (no pun intended), but it shouldn't cool it so much as to make the temperature drop so dramatically. Okay, heater off, riding down the highway, everything normal, come to a stop and idle temperature starts falling slowly, but when I turn on the heater the temperture starts falling faster.

My diagnosis: I have no leaks of anti-freeze, checked and re-checked. I have no symptoms of a blown head gasket, no milky white appearance on dip stick indicating anti-freeze mixing with engine oil, no clouds of white smoke coming out of exhaust, checked tail pipe for anti-freeze, none found, no loss of power and no loss of gas milage. I changed the thermostat, like I said. Do not think it could be the radiator pressure cap, normally if the cap goes bad the system will have no pressure and the engine will overheat, the opposite of the problem. Water pump, normally if the water pumps goes the coolant will not circulate through engine and will over heat, again, not the problem I am having.

Could it be: 1. A long shot, I bought a defective thermostat and it is still staying open.
2. The temperature sending unit has gone bad, very improbable since it does register the correct temperature when truck is moving down the highway.
3. The coolant is spent, again unlikely, it has been in the engine only for about 3 years and still looks clean and green.
4. Have to have a cylinder pressure check to determine actually if the head gasket is really blown or not, which I doubt.

My conclusion is that I still have a huge air lock somewhere in the system and the engine is still not completely filled with coolant and when the rpm's drop not enough hot coolant is reaching the temperature gauge sending unit, but if that much coolant is not in the system, why am I still getting lots of heat blowing from the heater?

The vehicles cooling system is not that complicated and there are few parts involved in its proper operation, I think I have covered them all, but somewhere I am missing something to pin point my problem. If anyone has any ideas, it would be greatly appreciated. Thank you.

 

Could it be the water pump impeller is not pumping water very well? Bettter at high speed but not so good at idle and water temp drops when hot water is not getting to temp sensor. Its so cold or not idling long enought to be overheating.
Dave

 

I have a '97 2.3 that acts about the same way.I bought it from a dealer a couple of years ago with 27,000 miles on it.I called the former owner from the dealer's office and he told me the truck was perfect except the heater never had worked very well and he never worried much about it,likewise I never thought much about it.He lived in the same city he worked in so I just figured it didn't have enough time to warm up.WRONG! I suffered through one winter with it then had the themostat changed and I think it is a little better.I really don't know the answer.I have a feeling its a common problem because I've heard of others having the same problem.I know that didn't help you any,but you know someone else has the same problem.Good luck!

 

did you put the proper temperature t-stat in?

#3 the coolant is suppose to be changed every two years. have you flushed the system?

#4 do a compression check to make sure everything is sound

 

On my 90’ 2.3l we have had the same problem. It only happens when the outside air temp drops way off the scale. We fixed the problem with a piece of cardboard. My dad would cover the whole radiator with the card board, and I with ½ to ¾ of coverage. In the hard cold snaps the power plant just would not make enough heat. The cardboard would not cause an over heating problem running around a small town, but a highway trip or towing is a different story. We lived in northern Michigan when we experienced the problem. Now that I live in central Utah I have not ever noticed the problem, but the winters are very mild in comparison. We have replaced the T-stat many times and even replaced the radiator once. Hope it helps, Da’Moose

 

From what I understand, the dash guages aren't very accurate. I wouldn't worry about it as long as you know that the t-stat is functioning and is the right temperature stat. If there is something wrong with your cooling system, you'd be overheating, not the opposite. The thermostat is what insures that the vehicle maintains the right temperature. If it's not opening then you'd be overheating, and if it is working right, then you can be pretty sure that you are running at the right temperature. My Ranger 4.0 always reads closer to the cold side of the guage. For a while I had a 180 stat in to see how it affected performance. With it in, the guage would hardly move. Now I have the 198 stat in like it's supposed to. Also, if you were running too cool, you'd be getting lower gas mileage because the ECU richens the mixture until it reaches optimum temperature. If anything it would probably be the sending unit, which only affects the guage.

 

I'd check the sending unit if everything else looks good. Although the coolant sending unit is a little bit of a pain to get to, its cheap.

My other thought would be the thermostatic fan clutch is busted and the fan is spinning at full speed all the time. On a cold engine, with the engine off, you should be able to turn the fan with a very light drag. If it seems to be locked up, replace the fan clutch. It isn't uncommon for the fluid in them, which doubles as the lubricant for the bearing in it, to leak out and cause the bearings to seize up. In cooler weather the engine may take a VERY long time to heat up if this has happened.

 

Thank you all for the replies, much appreciated.

The fan clutch is spinning freely with engine off, so it is not siezed up, but an excellent thought that I missed. I am beginning to believe what Dave posted about the water pump not pumping enough warm water through the system. I was out today with the truck and got it up to normal operating temp, as soon as I pulled into the driveway and let the engine idle, the temperature started to drop down towards the Cold mark, and rather quickly I might add. This leads me to believe it is a circulation problem dependent on engine speed. The impeller is turning somewhat at the higher rpm's, but at idle and lower rpm's it is not turning at all and not circulating the hot coolant through the system.
Now the problem I have with my theory, and Dave's, is why isn't the engine overheating at idle if the impeller is not circulating the coolant? Wouldn't it get overly hot from not circulating through the radiator and getting cooled off? Last two days temps here have been between 20 and 30 degrees, not bitter cold and normally the truck would heat up fast in these temperatures. Also why when turning on the heater it cools off even faster at idle?
I am not about to start changing parts indiscrimantly if I am not completely sure if that is the problem.

As for what one post said:

"did you put the proper temperature t-stat in?

#3 the coolant is suppose to be changed every two years. have you flushed the system?

#4 do a compression check to make sure everything is sound"

I kind of ignored any of this. The parts store only had one listing for thermostats for this vehicle and it was the standard temp thermostat.

Coolant is NOT supposed to be changed every two years, yes you can change your coolant every two years if you want to waste money and time doing it. Coolant will last as long as 5 years or more as long as your cooling system is functioning properly. Prestone guarantees 5 years minimum for their coolant. I have known people who NEVER changed their coolant and NEVER had a problem. Whomever says your coolant must be changed every two years must work for one of the coolant manufacturers, lol.

I have no signs of lost compression, engine runs great, no loss of power, and no signs of anti-freeze mixing with the oil.

I still have to think about the water pump theory or still could be as simple as an air lock still in the system. I might just drain the system and start over again, not because the coolant has gone bad, but because it may be the only way to get rid of a bad air lock.

 

Here is some explainations of my thinking.. mind you I am not at all sure about this, but is about all I could come up with.


"why isn't the engine overheating at idle if the impeller is not circulating the coolant? Wouldn't it get overly hot from not circulating through the radiator and getting cooled off?"

This gives me problems too!! LOL
The pump is circulating some water but not enought and its too cold outside to overheat. (also see below)



"This leads me to believe it is a circulation problem dependent on engine speed. The impeller is turning somewhat at the higher rpm's, but at idle and lower rpm's it is not turning at all and not circulating the hot coolant through the system."

I agree about the speed dependent idea, but it is turning at idle and some water is flowing but not enought. I have see pumps with a broken impeller vains and worn impellers that flow water, but not enought.


"could be as simple as an air lock still in the system. "

my experience is air locks work out after a heating cycle or two.


"Also why when turning on the heater it cools off even faster at idle?"

The amount of cooling the "heater" does stays about the same, but the heat produced by the engine is less at idle so it cools off at idle. Remember when you adjust the heat with the cab control it dosn't affect the flow through the heater core only how much warm get air gets inside the cab.

I hope this helps give you something to think about. I checked the the ford book and they say change the thermostat, a long procedure about checking the difference between fan speed and engine speed. and to check the engine temp with a different therometer. good luck.
Dave

 

There is one other thing to look at. Sometimes a radiator hose will collapse and restrict flow at higher RPMs. (letting it get warm at speed) and then flow more at idle (cooling off) but you would have a bad or low t-stat in you case.

a puzzler..

Dave

 

I am having the very same problem. Here are my symptoms.

1989 ranger 2.3L 2x4 with A/C

1. Engine runs cool. When running on "Key on engine on - KOEO" test the computer comes back with a 21 (meaning engine coolant temp sensor -ects) is out of spec. So I changed that sensor still same code.

2. I can block up radiator with card board and temp rises and no code 21. I can take away card board and temp goes down and I get code 21.

3. There is no "service engine soon light"

4. Temp gauge on dash reads low and erratic, see TSB 95132 950703 Temperature Gauge - Reads Low/Erratic. I may change this sensor but hard to get to.

5. Engine oil looks very good, no coolant in oil. I changed it anyway.

6. Ran radiator flush through it twice still same problem.

7. A Ford tech suggested I change the radiator, so I did along with hoses and heater hoses. Still same problem. Coolant is 50/50

8. I changed fan cluch.

9. All hoses are pressurized. The top hose is cool/warm to the touch. Like the thurmasat never opens. I have replaced it twice.. I checked both in boiling water before I installed and they worked fine.

10. I am tired of looking, but 200 mile a tank is not good and want to fix.


My theory could it be a dead cylinder, that 25% of the heat with this engine so no heat being produced and the cylinder it acting like a air pump keeping the engine below normal temperature. That would account for the bad mileage as well.

Please help

Andy

 

prestones website said
the extended life is suppose to last up to five years. the regular, change every year, for optimal protection. my ford manual says change coolant every two years. it does break down overtime.

for compression and t-stat, im just trying to help you rule things out.

 

Although I wouldn't expect a bad replacement thermostat, but you can take it out and easily test it.
Put it in a pan with some water and heat it up. You'll need a thermometer too. You should see it open at the specified temp. You want to make that it closes properly as well.

I just replaced mine in my 99 when the gauge was barely moving on cold days. I've also used the cardboard wired in front of the radiator in the past until I could solve the problem.

 

I am having almost the exact same problems with my '93 4.0 v6. i am quite certain it is air trapped! with my old thermostat, the temp gauge always stayed in cold. so i assumed it was stuck open. i changed it and it was stuck open. i put in a napa thermostat and the temp gauge climbed up into normal and then always fluctuated between hot and cold. sometimes rather quickly....like once a cycle. someone told me about the air bleed. the napa thermostat did not have one (thanks napa) so i changed it with a genuine motorcraft with a bleed. that was last weekend. i've filled the system a couple times and it stilll "cycles". it must be that there is a bit of air in there yet and when the air comes in contact with the sending unit, the unit reads cold. sending units read water a lot better than air. So i'm hoping it works itself out but i've driven it a lot and so far it has not improved one bit. i'm sure it's air related because it never did this with the old thermostat and that's the only thing that i've changed! i will keep you posted. KS

 

I've put 3 thermostats in my B4000. Same symtoms. I put Ford factory thermostats in every time. I don't know what the deal is, but everything is fine after replacement. They last about 2 years and they hang open I guess?? I have a friend with an Explorer with the same engine and he has had the same problem. The factory thermostat was recommended because some do not have the small vent hole at the top of the thermostat that it
instructs you to put in the up position.
Fishhead