4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

Cooling system problems need help!

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Old 02-09-2016
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Cooling system problems need help!

My 2008 ranger with 4.0 engine has 95000 miles and I have never had any issues until two weeks ago. Was on my way to work when engine temp. gauge spiked to high. Pulled over immediately and before I could kill the engine the temp went back to normal. Killed the engine anyway and checked coolant levels. Overflow tank was empty and radiator was about 1/2 quart low. Filled radiator to the top with prestone 50/50 and also filled overflow tank up to the cold fill mark. Check for leaks on driveway the next mourning and found nothing. Inspected for leaks under the hood and found nothing. Oil looks clean and free of coolant. Theres no smoke out of exhaust. Two weeks have gone by and radiator is still full but over flow tank is nearly empty again. Can any one explain this.
 
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Old 02-09-2016
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You have a leak.

Probably a hose spraying on to a part that is hot so it evaporates fairly fast, none leaks down to the ground.

And it probably only leaks when pressurized, so after warm up when engine is hot.

4.0l SOHC had a common leak point, the thermostat housing, coolant would pool under it on the intake and just evaporate, no leaks to the ground.

Good read here on that leak: How To Replace the Upper and Lower Thermostat Housing on a Ford 4.0L V6 SOHC Engine


If you can't see it leaking at that location then I would get/rent a cooling system pressure kit.
It is a rad cap with a gauge and a hand pump.
With engine cold you can pump up the pressure in the cooling system to 20psi, normal is 14-16psi, and then watch for leaks.
Engine being cold means you can run your hands over hoses and under water pump.
And leaking coolant won't evaporate, it will leak to the ground.
 
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Old 02-09-2016
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Originally Posted by RonD
You have a leak.

Probably a hose spraying on to a part that is hot so it evaporates fairly fast, none leaks down to the ground.

And it probably only leaks when pressurized, so after warm up when engine is hot.

4.0l SOHC had a common leak point, the thermostat housing, coolant would pool under it on the intake and just evaporate, no leaks to the ground.

Good read here on that leak: How To Replace the Upper and Lower Thermostat Housing on a Ford 4.0L V6 SOHC Engine


If you can't see it leaking at that location then I would get/rent a cooling system pressure kit.
It is a rad cap with a gauge and a hand pump.
With engine cold you can pump up the pressure in the cooling system to 20psi, normal is 14-16psi, and then watch for leaks.
Engine being cold means you can run your hands over hoses and under water pump.
And leaking coolant won't evaporate, it will leak to the ground.
. Thanks for the advice. I will continue to monitor the coolant levels until I can get time to bring it to my local ford dealership. I will ask them to pressure test the system for leaks.
 
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Old 03-06-2020
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Thanks for the posts on V6~4.0L~SOHC engines & TStat housings; good reference info.
Replaced the old leaking FRPlastic TStat Housing with a new Aluminum TStat Housing
in 2019Aug on a 2001 Ford ExSportTrac; no leaks as of 2020Mar after ~5K more miles.
My full write up with pics on that repair:
http://2001fordexplorersporttrac.fandom.com/Coolant_ThermoStat_Housing
 
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