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Discussion Starter #1
Hello everyone. This is my first post here!

I bought a 91 Dodge Stealth base model with the SOHC V6 engine.

I have been searching for diagrams but could not find any. I am curious if this white plugged sensor is the cooling fan switch, and if anybody knows if this is the right part? When looking for replacements online I have found ones that look similar with the white plug but are much shorter and do not stick nearly as far into the thermostat housing.

I replaced the two other sensors pictured in 1st photo to the right of the upper radiator hose, which if I am correct, is the coolant temperature sensor and the water temperature sending unit.

Is there an easy way to test if this fan switch/sensor is working properly? I have already sank way too much into this motor (had heads remachined with full valve job, new gaskets, timing belt, head bolts, radiator, etc.) and I am trying not to replace parts unless they truly need to be replaced.

Thank you for any and all help.
Cheers - Braden
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That sensor appears to be a coolant temp sensor for the AC system.
The fan thermostats (there are two) are both in the bottom of the radiator.
 

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That sensor appears to be a coolant temp sensor for the AC system.
The fan thermostats (there are two) are both in the bottom of the radiator.
When facing the front of the car, looking down at the radiator, there is a big fan on the left and a small fan on the right. The two temperature sensors are in the radiator just under the big fan.

The leftmost sensor is the low temp. Right most is high temp.

Both sensors are 2-wire connectors.

Disconnect the low temp (left most facing the front of the car). Turn the key on (engine not running), then place a paper clip jumper across the two wire socket. You should see/hear the big fan come on at low speed. This proves your fan works and relays work.

If your fan works, but after idling the car for 15 minutes with the sensor plugged in the fan does not turn on, then it is likely a bad sensor.

You could also put an ohm-meter across the sensor, but I was not able to do it due the tight working area.
 

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BTW: My knowledge is for a 92 stealth SOHC. I apologize in advance if your 91 turns out to be completely different from my 92.
 

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Discussion Starter #7
When facing the front of the car, looking down at the radiator, there is a big fan on the left and a small fan on the right. The two temperature sensors are in the radiator just under the big fan.

The leftmost sensor is the low temp. Right most is high temp.

Both sensors are 2-wire connectors.

Disconnect the low temp (left most facing the front of the car). Turn the key on (engine not running), then place a paper clip jumper across the two wire socket. You should see/hear the big fan come on at low speed. This proves your fan works and relays work.

If your fan works, but after idling the car for 15 minutes with the sensor plugged in the fan does not turn on, then it is likely a bad sensor.

You could also put an ohm-meter across the sensor, but I was not able to do it due the tight working area.
Thank you very much Matt for all of the information and your thorough explanation. Both year Stealths share the same engine so I believe everything should be transferrable.

I just tried what you suggested and I was able to get the fan to come on! This is the first time I have seen it turn on. So this means the fan motor and all of the fan relays are working properly?

The car currently has a blown head gasket, and I am trying to use some of the Bars Leak Head Seal product as a last resort. When I had car on yesterday for over 15 minutes idling in the garage (with tons of white smoke from the blown gasket), I never saw the fans come on. This is making me think that it may be a bad sensor.
 

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Thank you very much Matt for all of the information and your thorough explanation. Both year Stealths share the same engine so I believe everything should be transferrable.

I just tried what you suggested and I was able to get the fan to come on! This is the first time I have seen it turn on. So this means the fan motor and all of the fan relays are working properly?

The car currently has a blown head gasket, and I am trying to use some of the Bars Leak Head Seal product as a last resort. When I had car on yesterday for over 15 minutes idling in the garage (with tons of white smoke from the blown gasket), I never saw the fans come on. This is making me think that it may be a bad sensor.
Braden,

I was only able to help because I just went through this on mine. Someone had swapped the high and low temp sensor jacks so when the fan came on, it sounded like a jet.

Yes your fan motor and relays are working. The temp sensor may or may not be bad. Sometimes a blown head gasket can cause exhaust fumes to bubble into the bottom of the radiator. The exhaust fumes may prevent the temp sensor from triggering.

If you are still seeing tons white smoke (steam), then the temp sensor is the least of your problems. A while back, I used Blue Devil sealer to extend the life of a Ford Crown Victoria by more than 4 years. What I remember about it is that the problem went away within the first 10 minutes of idling even though the directions called for (and I gave it) 45 minutes of idling.

If you have applied the sealer already and you are still seeing an abnormal amount of white smoke then you probably need to apply it again. You can always turn the fan on with the paper clip if you need it to run during the application. Just watch the temperature gauge and turn the fan on when it gets too high. When you are applying the sealer, the thermostat should be removed from the car.
 

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Discussion Starter #9
Braden,

I was only able to help because I just went through this on mine. Someone had swapped the high and low temp sensor jacks so when the fan came on, it sounded like a jet.

Yes your fan motor and relays are working. The temp sensor may or may not be bad. Sometimes a blown head gasket can cause exhaust fumes to bubble into the bottom of the radiator. The exhaust fumes may prevent the temp sensor from triggering.

If you are still seeing tons white smoke (steam), then the temp sensor is the least of your problems. A while back, I used Blue Devil sealer to extend the life of a Ford Crown Victoria by more than 4 years. What I remember about it is that the problem went away within the first 10 minutes of idling even though the directions called for (and I gave it) 45 minutes of idling.

If you have applied the sealer already and you are still seeing an abnormal amount of white smoke then you probably need to apply it again. You can always turn the fan on with the paper clip if you need it to run during the application. Just watch the temperature gauge and turn the fan on when it gets too high. When you are applying the sealer, the thermostat should be removed from the car.
This car has been nothing but problems, but it has been a fun project and I have learned lots...for better or worse.

The previous owner overheated the vehicle on the way delivering it and blew the head gasket.This was back in July when I didn't realize the severity of that and exactly what a blown head gasket was. The owner kinda screwed me over in the long run.

I tore apart the interior as well as the motor. I got the heads remachined/resurfaced with a new valve job, then replaced the head gaskets, radiator, thermostat, timing belt, timing tensioner, spark plugs, and a bunch of gaskets with a buddy from high school who has owned multiple 3000gts and is quite familiar with these cars but not the SOHC engine.

After putting everything back together, the car is still experiencing symptoms of a blown head gasket. I'm assuming I did not clean the block well enough, or that the heads had slightly warped to the block and with the new remachined heads, they are not making a proper seal. The front three cylinders read 120, 90, and 90 psi in a compression test. Not very inspiring...

I am really hoping that the gasket sealer works. I bought the Bars Leak brand and went for the heaviest duty stuff meant for the toughest leaks. My plan is to run it through the engine once I am sure the radiator fans are working properly so that it will be able to circulate properly and not overheat in the process while idling in my garage.

Thanks for the tip about taking out the thermostat. I was wondering about that. Is that just so the gasket sealer can pass through more easily to seal up any leaks? I am hoping it does not plug up my new radiator that I have just installed. That is my only reservation to trying this method. And this method sure beats buying a replacement motor at the junkyard for $500 and swapping it. If the gasket sealer does not work, that is my next plan.

Main Question: Is there a way to test those temp sensors at the bottom of the radiator? I was planning on picking up a radiator from the junkyard in my town tomorrow that has a 92' Stealth with a motor that was supposedly running well in the car. Either way it comes with a 6-month warranty. Since I just replaced the radiator with a new unit, I am getting this one just to take the sensors out and exchange them into my radiator to see if it solves the problem.

I would like to confirm that they are the true culprits to the problem before I spend $50 on a junkyard radiator. Thanks again for all the help.

- Braden
 

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[QUOTE="braden_rendano, post: 1056336252, member: 144247"
Main Question: Is there a way to test those temp sensors at the bottom of the radiator?
- Braden
[/QUOTE]

If you pull it out of your radiator, you could connect the two pins to an ohm meter, then dip it in boiling water. It should show open when it is cold and closed (continuity) when it is in the boiling water.

There is both a high and a low temperature sensor. The high is a backup for when the low fails or a super-hot day comes along. Hard to believe both would have failed.

On the car I sealed, I think the sealer partially blocked the heater core. It did not damage the radiator. You could bypass the heater core by connecting the in/out lines together. Pulling the thermostat I think ensures the engine sees a correct mix of water and sealant as soon as it is started.

Good luck. These cars can really eat up a lot of time and money.
 

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Discussion Starter #11
Thanks for all the help Matt. This was super helpful. I conducted the process you recommended above and found that both sensors were working as they are supposed to. At this point I have seen/heard the fan kicking on so I know everything is functioning.

I have put about 180 miles on it the past couple of days! Before that, the car was driven into my driveway by the previous owner and I have been working on it in the garage ever since.

I am going to buy a compression test kit to see if the cylinders are properly sealing. I used the Bars head seal product as a last resort to see if it could solve my issues with the head gasket leak and it appears to have worked fairly well. The heater core isn't even clogged up which I appreciate since we have been getting some chilly weather in MA already.

However, I am occasionally getting some gray/bluish smoke out of the exhaust, particularly with hard acceleration and taking off in first gear. I think that the piston rings may be bad and the engine is not putting out proper compression and therefore not running very efficiently. I also have either a bad IAC valve, throttle body gasket, or leak in the intake because occasionally when idling, the car shuts off on me. Other times it runs perfectly fine. With all the money I've spent on this engine, I think it might be time for a new motor soon...

- Braden
 

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I'm glad to hear your car is running.

The '92 I have been helping with (it's my son's car) has finally been driving without problems for 2 weeks now after spending about a month working on it. Too many problems to mention.

It has 170K and the engine seems to be in good shape. No oil burning or ticking noises. I guess the life of the engine probably depends on how well the previous owners took care of it.
 

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Thanks. Sadly she is parked back in the garage at the moment. I am checking distributor timing and going to perform another compression test to see if it has improved since I put in the head gasket sealer.

Ah sounds like a nice father/son project. Has he been helping you with it too? Do you have any pictures of the car? The first gen Stealths really are beautiful looking cars. Even the base models look pretty good to me. I've heard that the SOHC motors can run a long time if properly maintained.
 
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