Hi guys! New member here..

I have a 1999 Ranger XLT, she's a 3.0L V6 FF...

As of Thursday I've been having problems with my temp gauge reading that my truck is overheating. This has never happened before so naturally it freaked me out.
i noticed that within 10 minutes of me driving she would almost reach Hot on the gauge and when ever I stopped at a light or slowed down the dial would slowly drop down to normal but would then rise up again.
Ive had issues before with my timing cover leaking, but at the time I couldn't afford a $1200 repair so the mechanic told me to buy K-seal and hope it would stop up the leak. It worked and so far no problems.
I sat under my truck for a good 10 minutes when I got home and no leaks whats so ever! I checked my resevoir and I'm full on coolant. I checked my oil and its full and no "chocolate milk of death". So I'm completely confused.
I turned her off and waited another 15 minutes to see if anything leaked and absolutely nothing. I thought maybe my thermostat got stuck or it was just one of those "weird" things vehicles randomly do.
The next day while driving to work (I live 10 minutes away) my gauge did the same thing. On the way home it rose up to H but as soon as I dropped my speed and rode 5 under the speed limit (I know, I know, but I was freaking out trying not to "blow up") she dropped and stayed at normal. The dial bounced a little but stayed relatively in the middle.
I noticed when I shut my truck off the dial doesn't drop to C like usual...it just stays where it was when I parked...but when I turn her on the dial drops below C until she warms up like usual.

My boyfriend is going to school as a diesel technician and suggested it was my ECT Sensor as did another mechanic. I'm not going to lie I'm not very mechanically experienced but I heard Rangers are notorious for ECTs going out. I still think my thermostat just finally kicked the bucket and won't open for my engine to cool.
I bought my truck in November of 2017, my first vehicle so naturally she's my baby haha. She has 108k miles and if it helps my transmission does jump when shifting to 1st and 2nd gear, so I just get off the gas and let it shift on its own.
I really hope I don't sound stupid or crazy, as girl who's dad taught her nothing I'm really trying to learn as much as I can so my kids won't be clueless like me.
Thanks for any help or suggestions ❤ Lucille (my truck) and I appreciate it!

 

Welcome to the forum

ECT = engine coolant temperature

There are TWO of these temp readers on your engine
ECT Sensor, it is used by the Computer ONLY, not the gauge
ECT Sender, it is used ONLY by the gauge

They look similar but are different inside, not interchangeable

The ECT Sender will be located on a hex shaped pipe coming out of the front of the lower intake manifold.
Find the thermostat housing, to the drivers side of the housing you will see the ECT Sensor
Look in front of housing and you will see ECT Sender on the pipe

A parts store guy will ALWAYS give you an ECT Sensor the first time out, even if you say S E N D E R in clear english, lol
Open the box
Sender will have cylinder shaped end, that goes into the coolant
Sensor will have Cone shaped end

I would replace thermostat, if you replace sender, it may be stuck 1/2 open, not closed
Engines generate lots of heat above 1,500RPM so thermostat must react and open more as needed, the fact temp gauge is going up and then coming back down means t-stat is open at least a little bit.

Could be electrical?
Unplug connector on ECT Sender and make sure there is no corrosion on terminals
The quick movement of temp needle on gauge reads more like electrical response than engine temp response, i.e. once engine gets HOT it takes a longer while to cool down that you are reporting

 

Thanks for the quick response! My boyfriend test drove my truck and brought it up to 70mph and said the dial never reached H like I was saying, but took a long time to warm up. I swear I'm not crazy about the over heating. He did mean to say it was my ECT Sender he thought was bad (sorry for the misleading the info lol) and that the brass is roached and corroded and looks like someone has already tried to mess with it because it did look stripped in some parts. I told him that he'd might as well replace my thermostat too just to knock out two birds with one stone.
he's gonna replace everything tomorrow so hopefully this issue is a tiny problem and not something more that I can't find without breaking some parts down!

 

My gut instinct is stuck T-Stat.
Generally speaking when these sensors degrade they read *lower* than actual.

Also, should it get to hot again... turn the heater on full blast. If that alone drops the temp that you know you have a cooling restriction somehow. (stuck T-Stat, blocked radiator, collapsed hose, too low of coolant, ect...)
If turning the heater on full blast doesn't drop the temp within a minute or two.. then I would suspect electrical.

Let us know what he finds.. inquiring minds want to know.

 

As far as I know my heater doesn't work we've tried to fix it but we can't seem to find a clamp small enough for the hose. I guess the person before me snipped it.
I live in Florida so thankfully in place of my heater my A/C blows like Alaska.

He's so stuck on it being the ECT Sender but I REALLY think its my Thermostat..he's just so stubborn but hey I'm the one paying for the parts...
I appreciate the suggestions! Im so glad I dont sound like a crazy female nutjob. I'll definetly update y'all soon!

 

You can't Block off the heater hoses on your vehicle, or you WILL get up and down temp gauge

The heater hoses from water pump and intake MUST always have flow

Your 1999 3.0l will have a 4 hose Bypass valve, vacuum controlled.

It allows coolant to flow whether you use the heater or not, coolant either flows thru the heater core or it doesn't, but it always flow between water pump and intake

Not sure what hose is not connected?

Some 3.0l had "T"s on the heater hose to circulate warm coolant thru the Throttle body, upper intake, this was because there was a freezing air issue in Northern climates, these can be block off