So, driving home today from work I started to smell some burning coolant/oil. I paid no mind right away, because the car in front of me was an old Vette and was smoking a bit, so I thought it was him. After a few miles of passing him, I keep smelling it and LUCKILY for my scangauge, I noted the coolant temps going above 205 (206, 208, 214...up to 225). I pulled over, popped the hood and noticed coolant spray over the center/front of the motor.

I was a bit pissed, because I was still about 15 miles from my house, so I turned the heat on blast and babied it home. Only one time did it get up to 230, by which the factory needle THEN moved ever so slightly. Factory tolerances for gauges SUCK!

I was able to get it home and did a quick youtube search for 4.0 L Thermostat DIY and say it was pretty easy. Got the housing out, so am going to replace them all tomorrow (housing, thermostat, both sender/sensor units for coolant, coolant (obviously) AND...the pcv valve, since this is the perfect time to do it. No need to worry about coolant loss :).

So, tomorrow I'll get to work on it after work, so shouldn't take long if all just falls into place...... Going to give the oil a good Seafoam flush and change with some Mobil 1 Extended Syn 5W-30. I've been using synthetic since I bought it last November, so I'm sure the thermal breakdown properties helped as the motor heated up a bit.

If you think of anything else I should check/change at this time, let me know. I was going to do the radiator, fan clutch and water pump too, but gotta hold off until next pay check. Go figure that it happens the day after I buy a new Trek mountain bike!


Parts list picked up from Advance Auto:
2L5Z-8592-BB - Thermostat housing from Ford, $57.69
1L2Z-8255-AA - Thermostat housing base gasket from Ford, $6.14
3L8Z-12A648-A - Coolant sensor/sender from Ford (need 2, both are identical part numbers), $36.35 each
13649 - Thermostat (190), $17.99
PCV483 - PCV Valve, $6.99
10233 - Radiator Cap, $7.49
35617 - Thermostat Gasket, $1.99

 

That's surprising that it took that much change for the factory needle to move.

 

Yeah, I'm not a big fan of that. I had cooling system issues in my old car (Scion tC) and luckily I had the scangauge reading coolant temp. Unfortunately for the tC, the aluminum block/head mixed with 235 degree temps was enough to rip out the head bolt threads and have a nasty head leak.

No oil noticed on the Ranger, so hoping for the best once I clean it all up tomorrow. I checked the oil and didn't notice any bubbles or foaming from coolant contamination.

 

Got it done in about 2-3 hours today; not bad. The housing is a b*tch to take out and even more of a pain to put back in (without snapping the plastic tabs). After it's back in, the rest is cake. Runs great and due to the 190 thermostat vs the 195, temps are about 5-7 degrees cooler. Definitely keeping my scan gauge hooked up since it saved me this time.

Broken housing (see the separation of the plastic?)


Exposed housing section


Inside view from under the intake manifold upper plenum. Coolant sprayed straight back.


Old PCV (replaced.....gunked up and noticed some clean oil spray in the intake manifold from the PCV hose. Seafoamed it, so it's all good now.)

 

not uncommon at all.

and yes, ranger guages take a good 25* before they move. my truck was at 240 once before the gauge decided to let me know.

 

Does anyone know of a metal housing replacement? I'm going to search Google, but just wondering if anyone knew of it.

 

havent seen one. it would be tough to shape metal to do that, but you could have one made im sure. for what the stock are worth, its easy to replace and pretty cheap. ill probably go pickup one as a spare to have on road trips.

 

This might be a little too late, but i did mine not too long ago and if i were you, i would change out the 2 small hose sections on the top and bottom of the housing. Mine were dry and thinning when i changed it.

 

Yep, this is a common issue, did mine a couple years ago. I had mine off twice, once was to change the gaskets thinking that was the issue but it wasnt, it was leaking at the seam just like yours. It was such a pain in the dick to get it out and back in the first time that the second time I removed the intake plenum, that made it a **** ton easier to do that go around.

 

 

I wanted to take the plenum off like you did, but wasn't 100% sure how much extra work was involved and had to get it done fast. Next time, intake will be coming off and will also be thoroughly cleaned :).

 

I know this thread is a week old, but I thought I would add my 2 cents. I have had to replace the thermostat housing 3 times and I only have 140k on my truck. Now the truck did overheat one time because of a crack in the radiator. I replaced the radiator and thermostat housing and no more than almost a month it had busted again. Thus replaced it again and replaced the assembly again. Finally on the third time I replaced everything. Thermostat housing, thermostat, both sensors, heater hoses, upper and lower radiator hoses along with the water pump and hoses. Everything that handles water on my engine is now brand new lol. I replaced the PCV valve around 135k.

All that to say, I hope you don't have any problems ever again on your truck! But def keep an eye on it just to he safe!

 

I keep an eye on my scan gauge constantly. I cruise at 188-190 in 85 degree ambient temps due to the 190 thermostat I put in. If the temp goes up above 195, then I know there's something more to pay attention to.

Also, on a side note, after seafoaming the intake manifold when doing the thermostat and changing all of the coolant out.....I ended up with 19.8 mpg on the last full tank. I've had the exhaust on for at least 4 tanks now, so that should have calibrated accordingly by now. So, hooray for more mileage :)

 

Sounds good to me. I put a 190 degree thermostat in the last time as well. And as you do I keep my eye on my ultragauge of the water temp. Not letting anything bad happen again!

Dang sounds like some great gas mileage! I have been getting 15.5-16 all the time lately. Nothing I can do about I reckon lol.

 

I did the thermostat housing this past weekend. It had ruptured in the same place. Ended up needing to take the intake plenum off because the area was so hard to get to. We also tore off one of the bolts that holds the lower housing in, and needed to fill and re-thread that. We replaced the housing, thermostat, upper and lower hoses, and the bypass hose. Put everything back together except for the thermostat and gasket, went to flush the system with water, and it waterfalled down over the engine block to the ground. We figured it must just be due to not having the gasket in, but we didn't realize how much of an impact that would have, does anyone have an opinion on that?

 

I found the company out of Memphis Tennessee, they make a metal housing for the thermostat upper and lower, it's a little bit more expensive but he guarantees that you won't have the issue of it leaking at the lower housing anymore I just ordered it and I'm waiting for it to arrive I will advise everyone on how it looks and how it fits as soon as I receive it. The price was $149.99, and I purchased it at simmonsautosportz.com, the guy that I spoke with was very knowledgeable and extremely courteous and all the reviews that I have read on this product rated at five stars and everyone is happy with it, so stay tuned and I will let you guys know what I think of it and how well it works and hopefully this can alleviate others headaches and problems they have had with this horrible design by Ford

 

That wouldn't be a bad idea, I've heard of a lot of people who have had to replace the thermostat housing because it cracks. I have a 4.0L v6 OHV engine now, and the thermostat "housing" is a part of the hose, kind of. It's all metal, which is lovely.

 

I replaced my leaking T-stat housing with a simmonsautosportz .com aluminum unit several years ago and is great compared to the cheapo oem unit.

 

Thanks to Tatooedmick76 for mentioning the metal replacement t-stat housing.
Thanks to derangered for bumping this thread back into daylight by posting.

The simmonsautosportz part is duly noted in my "Ranger Notes".
Ford should send the owner of every so-effected engine a voucher for one of these metal replacement parts.
They ought to be able to manufacture a box for Heaven's sake.

Q: With the new metal housing, is it still necessary to remove the intake plenum?

 

You can swap the housing out without pulling the intake , it is a challenge though. If I had to do it again (glad I don't) I would remove the intake.

 

Is it an access to the housing's bolts issue or difficulty with attaching the wee bypass hose?

Don't get me wrong, I'll remove the intake. I'm convinced.

 

General access. Bolts, hoses and getting a proper RTV seal without smearing it all over. Wee bypass hose. Blimey!

 

Thanks for the posts about the thermostat housing on the V6~4.0L~SOHC engines.
Replaced a leaking old FRPlastic TStat Housing with a new Aluminum TStat Housing
in 2019Aug on a 2001 Ford ExSportTrac; no leaks as of 2020Mar & another ~5K miles.
Here's my write up on that: http://2001fordexplorersporttrac.fandom.com/Coolant_ThermoStat_Housing