Do I need to replace my thermostat?

[Metal Geezer]

Any others experience this?
As my engine warms upon my 20 minute drive to/from work, the temp gauge rises to “about” 1/4, then falls back to almost C. Stays there for a while, then slowly recovers to normal operating temperature just below 1/2. I can feel it in the cabin air temperature as well.
(Apologies ahead of time for the suspect picture quality)

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[LawnMM]

Possible, it might be getting stuck open. I can look up the check process tomorrow but Airline Tech will probably be at me to it

 

[Andrew27]

Any others experience this?
As my engine warms upon my 20 minute drive to/from work, the temp gauge rises to “about” 1/4, then falls back to almost C. Stays there for a while, then slowly recovers to normal operating temperature just below 1/2. I can feel it in the cabin air temperature as well.
(Apologies ahead of time for the suspect picture quality)

Make sure your coolant level is full first. If so, replacing the thermostat would be the next step in my opinion.

 

[airline tech]

Could be stuck open, but I would check the coolant level & pressure test the system (If low)
including the cap.
Fluctuating gauge - could be low coolant and or air pockets in the system, but being it never reached operating temp - most likely stuck open T-Stat, not as common as stuck closed, but it does happen.

 

[Metal Geezer]

Thanx for all your input.
I have verified that coolant is just below “max” in the degas bottle, but I don’t have the tools to pressure test.
On tonight’s drive it behaved normally after 3 consecutive days of foolishness. (This happened a couple of times last winter but more randomly. Normal when I took it to the dealer of course). ?
I’ll likely change thermostats when the weather warms a bit.
Thanx again!

 

[Colo_Ranger]

Thanx for all your input.
I have verified that coolant is just below “max” in the degas bottle, but I don’t have the tools to pressure test.
On tonight’s drive it behaved normally after 3 consecutive days of foolishness. (This happened a couple of times last winter but more randomly. Normal when I took it to the dealer of course). ?
I’ll likely change thermostats when the weather warms a bit.
Thanx again!

Just for reference sake, the coolant has been low in every Ranger I have seen (from the factory). You should top it off, no matter what. I wouldn't consider that to be a leak...

 

[Blue Streak]

Back in the 70s we put 3 thermostats in my dads 74 F150 in 3 days. He had a 60 + mile drive home every day & this was the winter. Fortunately they all stuck open.

 

[DukeCanBuildit]

Back in the 70s we put 3 thermostats in my dads 74 F150 in 3 days. He had a 60 + mile drive home every day & this was the winter. Fortunately they all stuck open.

Ahhhh, the 70s - the days of changing thermostats every Spring and Fall. That’s when I learned how not to tighten down a thermostat housing. ?

 

[Dereku]

Ahhhh, the 70s - the days of changing thermostats every Spring and Fall. That’s when I learned how not to tighten down a thermostat housing. ?

I had a few thermostats back in the day that might have had a single oversized bolt or if I could a through bolt and nut lol

 

[ronranger]

In cold weather my thermostat works a lot like yours. Good luck.

 

[Grandaccess]

Mine too, I never thought anything of it, it never gets to half way

 

[Kawffin]

Im having this same issue but mine is throwing a check engine light. My thermostat was replaced last year by the dealer so im guessing it's a faulty thermostat.

 

[RangerBill]

Im having this same issue but mine is throwing a check engine light. My thermostat was replaced last year by the dealer so im guessing it's a faulty thermostat.

You should read the DTC codes and report them here.

 

[Kawffin]

You should read the DTC codes and report them here.

 

[RangerBill]

Could be a bad thermostat. From the shop manual:

Gasoline Engines PCED
P0128 - Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature)

Description: ​	This DTC sets when the thermostat monitor has not achieved the required engine operating temperature within a specified amount of time.​
Possible Causes: ​	Insufficient warm up time Low engine coolant level Leaking or stuck open thermostat Damaged engine coolant temperature (ECT) sensor Damaged cylinder head temperature (CHT) sensor

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