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Thread: Car is running a little hot

  1. #11
    Senior Member
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    The fans cycle on and off by the "O" switch AND the A/C. Another reason you need the A/C to also cycle, so the fans can cycle AND you don't freeze up the evap coil. The whole thing is kind of Rube Goldberg, the way everything affects everything but nothing "talks" to each other the way new computerized cars do now. The A/C doesn't know what the "O" switch is doing and the "O" switch doesn't know if the A/C is on. As for oil temp, Ron is correct. If the thermostat is closed the fans aren't cooling the coolant because it isn't circulating in the radiator. That is why the "O" switch isn't supposed to turn the fans on until after the thermostat is open and turn the fans off before the thermostat closes. Here is a case of where you should get these parts from one of the Delorean vendors so you get parts that can work together properly. The settings for the thermostat and the "O" switch matter for everything to work right. And you do NOT want the fans cycling on the cooling fan circuit breaker. Very bad.
    David Teitelbaum

  2. #12
    Senior Member Jimmyvonviggle's Avatar
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    Thank you all for your comments. My temperature gauge has always been accurate and a laser thermometer has verified this. I think it is a terrible idea to bypass the otter stat and run the fan all the time.

    The problem was the fans would kick on inconsistently and run for a very short amount of time. This is something I just noticed in the last 2 weeks. I also noticed more heat coming off my engine after stopping the car and raising the engine cover. I decided to replace the 40 amp circuit breaker. This now makes the fans operate as they did before.

    The reason why my engine feels hotter is a bigger issue I will have to address. The engine is leaking a small amount of oil from the crankshaft pulley (I could be wrong but it appears from this area) and it is turning into a powder that covers the engine. I believe this is causing the engine to smell or give off more external heat in the engine bay.
    Barry

  3. #13
    Administrator Ron's Avatar
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    Quote Originally Posted by Helirich View Post
    The thermostat does that.
    The thermostat only sets the floor for coolant temp! Once open, it is then up to the design of the rest of the system.

    Quote Originally Posted by Helirich View Post
    There really is no reason the water can't be cool all the time.
    Sure there is. The majority of wear happens when the engine is cold! It needs to warm up quickly (parts need to expand to size, oil needs to get to optimum temp range, O2 sensors need to heat up quicker on some. Not to mention trans oil and cabin heat...). That's the thermostat's only job.

    It's not an either-or thing -- The coolant passages, fan(s), radiator (its flow, both air and coolant), thermostat all work in concert by design to keep everything within range.

  4. #14
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    Quote Originally Posted by Helirich View Post
    There really is no reason the water can't be cool all the time.
    Quote Originally Posted by Ron View Post
    Sure there is. The majority of wear happens when the engine is cold! It needs to warm up quickly (parts need to expand to size, oil needs to get to optimum temp range, O2 sensors need to heat up quicker on some. Not to mention trans oil and cabin heat...). That's the thermostat's only job.
    .
    Let me rephrase that. There is no reason that the water in the radiator cant be cool all the time. In fact, it would help the thermostat do its job.

  5. #15
    Administrator Ron's Avatar
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    Quote Originally Posted by Helirich View Post
    Let me rephrase that. There is no reason that the water in the radiator cant be cool all the time. In fact, it would help the thermostat do its job.
    ...It's not going to be cool all of the time if the thermostat ever opens.
    There's no way cool water in the radiator (or anywhere else) could help the thermostat bring the engine up to temp.

    Again, on a D, the system is closed, the thermostat activates (the rest of the system), not regulates. It just sits there open, once the engine is fully up to temp (except under extremely cold ambient conditions).
    On some non-closed systems, they regulate, E.G., some marine applications.

  6. #16
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    Quote Originally Posted by Ron View Post
    There's no way cool water in the radiator (or anywhere else) could help the thermostat bring the engine up to temp.
    The thermostat's job is to keep the engine temps within limits. It doesn't need help warming the engine, but the vast majority of the time it's trying to keep the engine from overtemping. Cool water will help. The cooler, the better. (As long as it's not freezing)

  7. #17
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    Quote Originally Posted by cdrusn View Post
    I always wonder why it's so important to let the mechanical and electrical systems determine what the temperature becomes. There are a lot of details that make the system run at a certain temperature. Thermostat opens and closes, fans come on or don't, radiator has no air pockets and is clean inside, a/c on or off, car is at speed or in traffic. Why don't you just avoid all of the worry about everything working as designed and just run a wire and bypass the otterstat and run the fans all the time? It won't damage anything and you won't have to worry about if your fans are on or off? Takes 30 seconds to run the wire and remove all doubt.
    Got to thinking about this. You realize that for probably 60 years, that's how it worked. You start the car and the fan is running. Lol.

  8. #18
    Administrator Ron's Avatar
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    Quote Originally Posted by Helirich View Post
    The thermostat's job is to keep the engine temps within limits.
    No, it's job is to get the engine up to temp as soon as possible.

    Quote Originally Posted by Helirich View Post
    It doesn't need help warming the engine.
    (You came up with that....because you have its main job wrong....)

    Of course it don't. Besides not doing any warming itself in the first place, from start up, the engine is creating the heat, while the thermostat prevents the rest of the cooling system from cooling. It begins to open at ~180F. At ~200F it is fully open, setting the coolant's floor temp. As the engine and oil continue to get hotter, the thermostat just sits there, fully open.

    Quote Originally Posted by Helirich View Post
    but the vast majority of the time it's trying to keep the engine from overtemping.
    No, the vast majority of the time it's wide open -- There is nothing else it can do once it's fully open *; the rest of the system is keeping the coolant (and engine) from exceeding the ceiling temp(s), where thermal clutch fans, Otterstats, or similar when equipped, is in control.

    (*Extreme cold, bad thermal clutch fan, bad electric fan control, early style poor design, etc., will allow it to shut, because it is too cold!)


    Quote Originally Posted by Helirich View Post
    Got to thinking about this. You realize that for probably 60 years, that's how it worked. You start the car and the fan is running. Lol.
    Lol, starting in 1901 (DMG)??
    Seems you have been thinking this way all along to me, while dismissing/ignoring the improvements made over the half century...

  9. #19
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    Splitting hairs now? Main job, secondary job, who cares? Cool water helps the thermostat do its job. Is it wide open most of the time? Yes. In the south for sure. In the not to far north, I assure you the thermostat closes or partially closes lots of times. When I was young and lived in Pennsylvania, I had a car that I ran with no thermostat. It ran fine all year long, but it sucked in the winter. (No heat) I've heard that no thermostat will give you bad mpg's, but I never noticed that. I've concluded the number one job of the thermostat is heat. Lol.

    In any case, you and I both know how the system works. I'm just pointing out that with the new brushless, low amp draw fans, there maybe advantage to just have them run all the time. I don't want to dismiss/ignore advances they've made in fan motors.


    Edit, I just searched three differnt venders for cooling fan motors. None of them say if their motors are brushless. It seems like they would brag about it. Does anybody know if/who has them? I'm contemplating getting a new radiator and fans. I would really like brushless.
    Last edited by Helirich; 07-22-2021 at 12:14 PM.

  10. #20
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by Helirich View Post
    Edit, I just searched three differnt venders for cooling fan motors. None of them say if their motors are brushless. It seems like they would brag about it. Does anybody know if/who has them? I'm contemplating getting a new radiator and fans. I would really like brushless.
    Have you looked at the specifications of brush-less fans? Just wondering what the advantage is. Maybe longer life since brushes may wear out.
    Dave M vin 03572
    http://dm-eng.weebly.com/

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