Thermostat housing gasket confusion - Ranger-Forums - The Ultimate Ford Ranger Resource


DOHC - 2.3L Duratec / Mazda L Engines Discussions and Topics specific to the Duratec 4 cylinder engines

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Old 02-14-2017
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Thermostat housing gasket confusion

I have a small coolant leak that appears to be coming from the bottom of the thermostat housing. I do not know if I need to replace the entire thermostat/housing or just need a new gasket. But while I am in there I might replace the entire thing. Anyway, when I look it up, there appears to be two different gaskets that look completely different. One is called "housing to head" and looks like a standard style flat gasket that doesn't have the right shape and has 1 too many holes:

http://www.rockauto.com/info/6/FELPF_35771_P04_TOP.jpg

The other looks like a rubber seal that would fit in a groove on the thermostat housing

http://www.rockauto.com/info/31/BA0396568-1.jpg


I am pretty sure I need the bottom one. But if that is correct, what is the other one for? Also, what is the best way to seal with the rubber one? Should I just use the gasket or should I add some blue rtv somewhere? Thanks.
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Old 02-15-2017
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What year is the 2.3l Duratec engine, 2001.5 to 2012, earlier used electric thermostats later just regular thermostats.

So year matters and could be transition year so..............

Image here of electric thermostat housing, you can see where rubber gasket goes: http://www.therangerstation.com/Maga...mostat/et1.jpg

Last edited by RonD; 02-15-2017 at 09:47 AM.
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Old 02-15-2017
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Mine is a 2003 and it is one with the electronic connector on the thermostat housing. What exactly does the electronic part do? Does it just read the position of the thermostat, or does it actually control the thermostat electronically? On Rock Auto it calls it a "Sensor" so I assume there is no control there.

It is odd that on Rock Auto they have some thermostats without the sensor (and they are a cheap) but most of them are with the sensor. I would assume you can't just put a non-sensor model on a truck that came with a sensor model. Was 2003 a transition year or does Rock Auto incorrect?

One other question. What is the OEM temp of the thermostat? The Motocraft model on Rock Auto is listed as 190, but the other ones claim "OE Temperature" and list it as 208.
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Old 02-15-2017
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No, they actually pre-heat the thermostat so it opens, sensor part is that it draws power, like heated O2 sensor draws power and you would get a code if it didn't.

Many use the unheated thermostat housing and just leave the old one connected by tying up out of the way.
Haven't read of any problems with doing that.

2003 was the year they changed to non-heated, so you must have an earlier 2003

heated thermostat would be rated as 208degF
unheated 180degF

On the 2.3l Duratec DOHC engine the thermostat is on the lower radiator hose, not upper hose like most engines.
The upper engine coolant needs to get to about 195degF before thermostat should open, so most Fords use 192-195degF thermostats.

Flow thru all radiators is HOT in at the top and COOL out at the bottom, and a radiator gives you about 15degF of cooling.

So if using a thermostat on lower hose 180degF would be the choice, that should keep upper engine coolant above 190degF, this gives best MPG and cleanest oil.

The electric thermostat pre-heats the coolant at the thermostat so they used a 208degF to offset that, don't ask me why, engineers do stuff on paper that don't make much sense in the real world.

But the 2.3l DOHC engine was put first put into Rangers in 2001.5 and the electric thermostat was only used until 2003.5, so just two years and the non-electric until 2012, so 8.5 years, last year of the Ranger

Your computer needs to see the power draw for this heater or it will turn on the CEL(check engine light) but you can use the 180degF thermostat and housing

Last edited by RonD; 02-15-2017 at 03:15 PM.
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Old 02-15-2017
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Thanks.

Mine definitely has the electrical connector on it.

I have the 2002 Ford Manual on CD and in the wiring diagram I can find the ECT sensor, connector, etc. But there is no mention of the thermostat or anything like that.

Last edited by lemmy; 02-15-2017 at 06:33 PM.
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Old 02-15-2017
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It has an ECT and CHT(cylinder head temp), also Electronic Thermostat

Thats the 2.3l DOHC Duratec engine

3.0l and 4.0l didn't have CHT or Electronic Thermostat

ECT is usually shown in Dash board wiring not in engine wiring

You leave the whole electric thermostat housing plugged in but moved over out of the way and secured.
And install the non-electric version
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Old 02-15-2017
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Thanks.

I finally found everything in the 2001 manual.

The thermostat is under "E" for "Electronic Thermostat". The 2 pins are the battery voltage and a signal from the PCM like you said.

The ECT Sender goes the the PCM (pin 19) and the instrument cluster.

Thanks for your help. I don't know why I have a leak there (gasket or something wrong with the thermostat), but I think I will replace the thermostat with a 2004 Motorcraft (non sensor) and leave the old one plugged in.
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Old 02-16-2017
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Here's how that electric thermostat works:

Quote:
The primary objective for the thermostat heater control is for improvement in fuel economy and thermal efficiency. The system consists of a high temperature (98C/208F in lieu of a 90C/194F ) thermostat (Figure 52) that has a resistive heater within the wax element. The heater is controlled by the PCM dependent on engine speed, throttle position, engine load, barometric pressure, air charge temperature, transmission oil temperature and engine coolant temperature.

During low speed, low load and low air charge temperature conditions, the thermostat heater is OFF and the engine is allowed to operate at an elevated coolant temperature. This should result in lower internal friction and higher thermal efficiency, both leading to improved fuel economy.

During high speed, high load, high temperature conditions (air charge, transmission oil or engine coolant), the PCM output is energized with a duty cycle to the thermostat heater. This heats the wax and forces the thermostat to rapidly open wider allowing extra coolant to flow from the radiator. This will reduce the coolant temperature and improve with performance demand.

It should be noted that the heater is only capable of supplying a SMALL amount of additional heat to the wax element; it is NOT capable of opening the thermostat alone. The thermostat is 100% duty cycle for short calibrated time and than the duty cycle is reduce to a maximum of 70% on and 30% off.

Approximately, unheated, the thermostat will begin to open at a coolant temperature of 98C (208F) and will be fully open at approx. 108C (226F) . Energizing the heater will reduce the opening temperature to about 68C (154F) and the fully open temperature to 103C (217F) .
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Old 02-17-2017
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Good write up

Unheated definitely has better numbers
Best MPG and cleanest oil starts at 195degF
200-225degF is where you want upper engine coolant temp, which is what those numbers represent.

People often confuse operating temp and overheating temp.

i.e. if you run an engine with upper coolant temp at 180degF it won't overheat as fast as an engine running at 210degF.

Which is TRUE but................it would give you about 10 extra seconds before BOTH were at overheat temp 250degF+

Reason engine over heats is loss of coolant or loss of coolant flow, and not related to operating temp level.
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