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Thermostat dropping temp for no reason?       #: 1026
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 Posted: Fri Jul 6th, 2018 01:24 am
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NewShockerGuy
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Got a weird problem going on with my 2001 2.3L XLT.

This happened once about two months ago and I didn't think anything of it.  Now it has happened multiple times and I am wondering what is going on.

I have an ultra gauge so I can see the engine temp.  It normally goes up to about 220' F.  Then will drop back down to about 200' like normal.  However what seems to be happening for no reason or randomly is that I see the temp gauge on the cluster start to dip below the middle point and when I start looking at the ultra gauge it drops temp to about 170-180' F.  I replaced the OEM thermostat with another OEM thermostat yesterday and it did it again today.  This seems to happen more when I turn the AC on to MAX and after about 35-40 minutes I can see the engine temp drop.  It doesn't drop below 170' F but I can't remember this ever really happening...  This doesn't seem normal to me.

No other sighs or problems just random.  I had to stop pretty quickly a few times and almost immediately after that I noticed the temp going down.  If I stopped abruptly again the temp would start to go back to normal.  I'm wondering if there is something along the lines of wiring but not 100% sure what to check.  Some days I can drive and nothing happens and the temp stays normal the entire time.  Other times the temp my dip below like the above but then after 20 minutes go back up to normal...

-Nigel



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 Posted: Fri Jul 6th, 2018 02:43 pm
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410customs

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Coolant level? If the sensor sees a pocket of air it will read funny
Sounds like your thermostat is full open by 210 and the water behind it is like 160-170 degrees so when that hits the sensor the temp dips?
Check coolant level make sure no air
Maybe time for a new radiator cap, as this controls the pressure in the cooling system and you have already done the thermostat.



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 Posted: Sat Jul 7th, 2018 06:29 am
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410customs wrote:
Coolant level? If the sensor sees a pocket of air it will read funny
Sounds like your thermostat is full open by 210 and the water behind it is like 160-170 degrees so when that hits the sensor the temp dips?
Check coolant level make sure no air
Maybe time for a new radiator cap, as this controls the pressure in the cooling system and you have already done the thermostat.

^^ This.

Definitely would have the radiator cap pressure tested.



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 Posted: Sat Jul 7th, 2018 07:24 pm
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A third here for radiator cap. There is a little valve in the middle that opens to let the fluid in the reservoir suck back in to the radiator when it is cooling off. If the seal gives out it will push fluid in to the reservoir overflowing it consequently losing small amounts of coolant each cycle, causing the air pockets eventually.

I cured a friends problem with his ranger after he had paid hundreds for a radiator, heater control valve and a couple hoses by replacing a $14 radiator cap for him.



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 Posted: Tue Jul 10th, 2018 10:13 pm
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I checked my coolant level and it's right at the min mark. I read several things stating that it shouldn't be filled to the max mark because of expansion. My 2001 has the degaus bottle with the rad cap built into the degaus cap. I don't have a normal rad cap on the radiator like every other car in the world..lol

I have replaced the rad cap about a year or so ago. Not sure how it could go bad honestly.

Today the temp dropped and it was right when I was on an incline hill going slowly (rush hour traffic) turning to the right. IE: hill that turns right (clockwise) via an on ramp getting onto the highway.

Started seeing the temp drop and it went to about 170' F. It was like this all the way home (about another 20 minutes) Prior to that temp was at 220' F like normal.

I keep the truck running while in the driveway. Pop the hood and look at things. I unscrewed the degaus rad cap, and what normally happens is that the coolant level goes up quite a bit. This time it did not. It maybe went up half an inch. I thought that was odd. Does that mean it wasn't building pressure or it somehow lost pressure?

I then felt the hoses. The top rad hose was hot, the bottom rad hose was somewhat warm/hot. Checked the hoses to the thermostat and the larger hose was warm, but the little hose didn't feel hot at all. I started squeezing all the hoses, then unplugged the connector on the thermostat, left it undone. Then went back into the truck and saw that the temp started to go back up on the ultra gauge. It was at about 200' F. I checked the little hose again on the thermostat and it was hot now, so clearly coolant was going through it. Plugged the connector back in. Drove to the gym about 20 minutes later and the temp was fine. Drove back home, again temp fine.

The rad cap is cheap I think at around $12 on ebay so that's fine I don't mind getting another one but just seems odd. Never had this problem before.

hmmmmm....?

-Nigel



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 Posted: Tue Jul 10th, 2018 11:06 pm
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Couple of things;

I think you should make sure the radiator is filled to the neck, do this when fully cold.

Fill the expansion tank to the full line, again, do when fully cold, otherwise you'll end up with the information you'd head about not filling it.

Not sure what cap you have, or why, but a regular cap for mine cost 4 or 5 from amazon and that was for a nice Gates cap.

Also, i see yours is the 2.3l but on mine, the overflow/expansion pipe running from the rad neck to the tank, had lost it's seal, so under pressure, i'd get weeping from both the underside of the expansion tank, as well as the rad neck. I just put jubilee clips on both connections, no more problems.



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 Posted: Wed Jul 11th, 2018 12:34 pm
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This is the cap/tank I have:



There is no way to fill the rad to the neck in terms of a normal rad/cap design.  By default the design that ford used on the above tank and rad it will naturally bleed out air pockets into the degaus tank.  I'll check the hoses again but everything was replaced 2-3 years ago with new hoses and clamps.  I just did all the overflow hoses this year with new clamps.  I'm wondering at this point if it's by chance weird electrical gremlins..  I kept getting a rear ABS speed sensor problem when I replaced my Rybestos ABS sensor on the rear diff to an OEM Motorcraft one... this was happening for a week or two.  Bought a new Rybestos abs sensor to replace the new Motocraft one and that ABS error code/problem went away and never came back.  

I wish my thermostat didn't have that stupid heater/electrical connector.  Ford did away with that after a couple years for a normal thermostat.
When I unplug it the truck does see that it's not there which is good.  But makes me wonder what might be happening.

-Nigel



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 Posted: Wed Jul 11th, 2018 03:12 pm
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As Madmaxx suggested... add some coolant to the bottle, maybe not full, half way between "min' and "full", watch what happens, if the coolant is pulled into the radiator then your system is other than reflected in the bottle.    If nothing happens then you still have room for expansion.

Yes you want expansion room in the bottle but the minimum level is just that a minimum, higher than min is better... IMHO !  Sort of like the engine oil, if it is at min... it is time to add oil !

I never liked the systems with the sealed caps... I would consider replacing the cap with something other than a seal cap, just me !

Engine Temp... I know the newer engine like it hotter but I was thinking 200 all the time is better than 220...(???), what about the Thermostat, have you replaced it recently ?

After reading your post about the temperature readings when you are going up hill, I am thinking as the others, coolant level is off !

How's your heater air temperature, if it goes cool and hot, then I would lean even more to the coolant level.



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 Posted: Wed Jul 11th, 2018 04:24 pm
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MaDMaXX

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Wait, did i misunderstand?  You don't have a radiator cap?

That is the part (radiator) i was saying fill to the top, not the expansion tank.

The expansion tank (part you pictured) needs to be filled to the top line, only when the engine is stone cold. 

I agree with Scrambler that it's a coolant level issue based on your descriptions.



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 Posted: Wed Jul 11th, 2018 07:30 pm
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Yes on the 2001 2.3L it does not have a radiator cap on the radiator at all.  The radiator cap is in the cap on the degaus bottle.  There's a thread somewhere on the forum where RonD goes into great detail about the degaus bottle and how it differs from a standard radiator/cap that is on every other ranger.  The procedure to fill the system and purge it of air is different compared to filling the radiator to the very top, while burping it, then putting the cap on and refilling the overflow tank.  The cap can not be changed to something different.  It has to be the specific bottle cap which does have the rad cap built in.

Thermostat was replaced but have the same problem intermittently.  I don't think it's a coolant level because it hasn't changed in terms of going down..etc.  If it was low on coolant wouldn't the temp go up instead of down?  Just trying to understand.  When I turn the truck on I can see coolant flowing back into the bottle and it does not dip down so I know it's not because it's too low.  I will fill it up between the max/min marks.  I've always kept it at min per RonD's explanation from years ago and never had an issue.


I'm going to replace the cap and see what happens.  Won't have it until next week when we get back from Cali... but makes me wonder wouldn't a faulty cap always be problematic.  There isn't a rhyme or reason why the temp drops at times.

When I turn on the heater the air is hot.  I've never had a problem with hot air.  Normally it's actually too hot, and I never turn the fan above setting 1 since the air is hot during the winter time.

-Nigel



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 Posted: Wed Jul 11th, 2018 08:16 pm
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Interesting.


I would check the hoses connecting it to the radiator, does the level in the tank change when you start it, or you just see it moving around?

As for temp changing, it depends of it's a lock of cold water, or a lack of water, thus nothing to transfer the hear to the sensor.



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 Posted: Fri Jul 13th, 2018 01:42 pm
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Sounds to me like an air pocket, air can get trapped in there, meaning it wont be burped easily
New thermostat may be suspect, I use Stant super stats when possible
If a thermo is suspect then you may want to look at it again and even boil it on a stove with a thermometer...it should be fully open at 195 degrees, of not then replace it
Your truck is running the normal operating temp range, so its not like this is a huge issue. 220 is high, but still considered normal operating temps.
What is the condition of your fan? Fan clutch? Shroud?



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 Posted: Thu Jul 19th, 2018 03:12 pm
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After more research it looks like the temps I am seeing at the CHT sensor are normal. Found what RonD stated:

"2.3l Duratec engines have CHT(cylinder head temp) sensor and some also had ECT(engine cooling temp) sensor, but not all, V6 engines all had ECT and no CHT
Whats the CHT showing at these times?...CHT sensor reads temp of metal in the head, not coolant"

I think what I was worried about was the truck running too hot but it seems like the CHT sensor is reading correctly.


I think I might have an air pocket somehow, but I think it was wiring. I'm still trouble shooting but it hasn't happened again, after moving wires around and ziptie a harness in place/out of the way.

Over the weekend I'm going to jack the front end up of the truck and try to work out any air pockets that might be in place.

I'll update if I find out any more information via trouble shooting.

-Nigel



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 Posted: Tue Aug 7th, 2018 10:57 pm
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Replaced the CHT sensor on the top of the engine yesterday. It's easy and cheap at $20... figured perhaps that is what is causing it. Drove today to work fine. On the way back, almost at the same area before the on ramp gauge dipped/temp reading did the same thing... so odd...

I'm completely drawing a blank. Checked the degauss bottle and coolant is at the upper mid/lower max line. So coolant is good. I even had the truck parked up hill the one day in the drive way with the heater on trying to see if it needed burped. Very hot heat, no issues or air that I could see that was trapped in system.

I don't know what else to check. All plugs and wires look fine. Get zero CEL lights/pending codes. I will get a CEL if I unplug the thermostat sensor plug which is good. Shows that it's functional but not sure why the temp keeps dropping like that.

No blockage in the radiator as that was replaced less than a year ago and when I drained out the coolant it was fine. No rust/nothing clogging anything.

Temp doesn't raise either or get too hot... so many threads on what is happening if the temp spikes or goes hot but not that much information on why it would drop, then eventually come back up to normal temp.

-Nigel



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