Looking for some help here as I have yet to get any solid leads. 2007 Ford Ranger FX4 lvl 2 with 230k km.

Swapped out the thermostat housing with the aluminum kit upgraded one (comes with thermostat, sensor and gaskets). Brand new and full of coolant.

For 2 months after the repair the engine ran fine, reached operating temps as normal. No signs of overheating or it running cold. Now winter is here, the outside temperature is dipping below 0 and I've noticed my engine is struggling to reach operating temperature. I brought it to a shop to get looked at and they didn't figure it out.

No matter what, the needle on the dash wont go up to half way mark. It will sit between 1/4 from cold and half. I have an aftermarket obd2 gauge and it will idle between 70-75°C. If I'm driving and I put my foot into it, it will go to 80°C but drops down soon after. I have heat in the cab, although I think it should be warmer. Otherwise the truck seems to run fine, no lack of power and not loosing any coolant.

Any thoughts on what or where to look at next? Best way to know 100% there is no air in the system?

 

It sounds like a bad thermostat.
Have you tried shielding your radiator with cardboard to see if the heater puts out more heat or if the gauge rises?

I saw the SA9 aluminum housing upgrade at simmonsautosportz.com. Is that the one you installed?

No mention of BRAND OF THERMOSTAT was made. Did it appear that the t'stat could be R&Red?

Installing a Motorcraft one would be my first step. What temperature I do not know (180℉, 185℉ or 190℉ ? )

Check to see if the moving part of the 'stat isn't hung up on the casting.

A cheap thermostat was installed in a neighbor's Toyota engine and this very same interference occurred.

 

Hi thanks for the reply!

The thermostat housing I got is from Austekk. Ebay link

It appears the thermostat is a 88°C unit where I believe the Motorcraft oem is 92? I still have the oem one so I can get it swapped out. Was just hoping I wouldn't have to dig into it again....

What is the purpose of the cardboard? If it runs warmer with the cardboard what would that mean?

 

Welcome to the forum

Yes, I would agree ^^^^

The thermostat is opening too far, or its broken and stuck open part way, which would be indicated by higher load causing temp to rise a bit, which is normal but it should drop back if thermostat opened more, while still under load.

It should come up to "operating temp" within 5 minutes of driving, just below 1/2, if its taking longer then yes t-stat is not closed all the way

Couple of other tests to do
After engine is cold, has sat overnight, open the hood and try to spin the fan, it should be locked, doesn't turn easily
Start engine and let it run for 1 minute, shut it off
Try to spin fan again, should spin easily, unlocked now
If not fan clutch is locked full time which can lower temp a bit

Start engine again and feel upper rad hose at radiator end, should be cold
Let engine run for 2 or 3 more minutes and feel again, should STILL be cold, if its warming up then t-stat is not closed, and it should be


It could have a 180degF t-stat
Stock t-stat is 195degF, 192-198degF

I would replace it just on speculation

Just FYI, t-stats are suppose to stay open when they fail, it's a "fail safe" mode, to prevent overheating

 

Amazing. Thank you for this super helpful. I will start taking a better look into it!

 

If you get a new t-stat get one with a "jiggle-valve", its a hole in the t-stat plate with a metal pin in it, the pin will "jiggle" to keep the hole in the plate open

What this is for is to let any air out of the engine side when refilling with coolant or any air that may have come in from a coolant leak in the engine side

If you can't find one with the jiggle valve then just drill an 1/8" hole in the plate, it lets the air out for the refill and usually won't clog up if coolant stays clean

In most engines you would mount t-stat with jiggle valve at 12:00, where the air would be, but on the 4.0l SOHC the t-stat sits flat so doesn't matter where its positioned, air would just be at the top of housing and would come out thru the hole

 

I appreciate you asking this question Jtremblay. I am experiencing the very same issue. Since this new long block installed 1,342 miles ago for the last 250 miles those very same symptoms I too have been experiencing. I talked with the shop that also installed the new thermostat housing along with the long block and they suggested that I try replacing the temperature sensor before doing anything else. Since that would require removing the housing to get to it I have now just decided to replace both the thermostat and the temperature sensor. Like you I feel as though even though I have warm air I feel it could be warmer.
Although I am pretty sure the three year warranty would cover this repair I do have some time today to do this one myself. Good Luck and also a thanks to RonD & Georgeandkira. I will let you know if this remedied the problem.

 

Changed out the temperature sensor and put a new thermostat (192 degree) in. All back to normal now. My guess is that the temp sensor was fine because I am really getting heat much hotter then it has been giving me. Needle on gauge is back to halfway.
The four month old thermostat must not have been closing completely is what I assume the problem was. It worked fine for the first three months.
Hope you get yours figured out Jtremblay, winter is fast approaching.

 

Good work

 

Thanks RonD. Hardest part was getting that clip back on that sensor. I almost went to purchase needle nose pliers that were narrower and longer but managed to get it in.

 

Ron said, "It could have a 180degF t-stat
Stock t-stat is 195degF, 192-198degF.

Tulsa installed a 192℉.
So the stock temp one is the one to install?
Stock is the way I'd go in the first place but there's a lot of learned knowledge here so that's why I'm asking.

 

Yes, Ford started using 195degF t-stats back in the late 1970's, early 1980's, after a study done by SAE,the Society of Automotive Engineers
Study showed this higher coolant temp range was better for engine life, cleaner oil and better MPG than the old standard 180degF t-stats

Most t-stat makers have 192degF t-stats models, but any deg between 190-200 is fine to use

t-stats are usually rated at +/-3deg for opening temp and +15deg for fully opened temp

Radiators are rated at -15deg with minimum air flow, and -20 to -25 with a fan pulling air thru them
So a working cooling system should stay within a 15deg range after full warm up