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  •  » ACP radiator drain thread size?

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    1/06/2025 9:53 AM  #1

    RTM
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    From: Cape Coral FL
    Registered: 5/22/2019
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    ACP radiator drain thread size?

    I'm not at home to check and I'm trying to order my fan controller from Auto Cool Guy.  He has the inline sensor that has an adapter you splice into your lower hose.  If the drain port on the radiator is 1/8 npt I can put his coolant sensor in place of the drain valve.  Just need to make sure it's at least 1/8 npt.

     

    1/06/2025 1:17 PM  #2

    Greg B
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    Re: ACP radiator drain thread size?

    A lot of confusion in the automotive industry about these two.  Better make darn sure.   A lot of fittings actually use nps because the taper can crack aluminium.   

    If multiple things can go wrong, the one that will go wrong will be the one that causes the most damage.
     

    1/06/2025 1:29 PM  #3

    Raymond_B
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    From: Fort Worth, TX
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    Re: ACP radiator drain thread size?

    What part# do you have? They have pretty good specs on their website. 

    https://buyacp.com/radiator/parts/cooling-system/?Make=Ford&Model=Mustang&Year=1965
     

     

    1/06/2025 1:32 PM  #4

    RTM
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    Re: ACP radiator drain thread size?

    Greg B wrote:

    A lot of confusion in the automotive industry about these two.  Better make darn sure.   A lot of fittings actually use nps because the taper can crack aluminium.   

     
    I myself am very aware of the difference.  I use to drill and tap both in my early machining days and even programmed cnc machines for both.   ACP says both the transmission ports are 1/8-27 npt.    Auto Cool Guy sells his probe sensor in either 1/8, 3/8 and 1/4 npt sizes.

       •Thread Starter
     

    1/06/2025 1:36 PM  #5

    Raymond_B
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    Re: ACP radiator drain thread size?

    I also meant to say, I ended up using Auto Cool Guy's copper inline sensor when I had that controller.

    https://www.autocoolguy.com/about

    Last edited by Raymond_B (1/06/2025 1:37 PM)

     

    1/06/2025 3:12 PM  #6

    RTM
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    Re: ACP radiator drain thread size?

    Raymond_B wrote:

    I also meant to say, I ended up using Auto Cool Guy's copper inline sensor when I had that controller.

    https://www.autocoolguy.com/about

     
    I don't think I can use the inline adapter on my lower hose.  There's not enough straight hose to place it.

       •Thread Starter
     

    1/06/2025 3:18 PM  #7

    John Ha
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    From: Mitchell, SD
    Registered: 4/02/2013
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    Re: ACP radiator drain thread size?

    Probably too late to matter but ACP has a Contact Us page with phone, email and a web form.  Why not ask them directly?

    Founding Member of the Perpetually Bewildered Society
     

    1/06/2025 4:02 PM  #8

    6sally6
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    From: Surfside Beach,SC
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    Re: ACP radiator drain thread size?

    Am I the only one who used a port in the intake ?!!
    I used a 160*sensor (I KNOW- I KNOW! ) from Summit. It screws right into a port in the rear-ish section of the intake.
    When the water gets 160*....fan comes on !
    I can't remember when it cuts off butt there are several on/off options available.
    My goal was to hide MOST of my wires under the hood.
    This sensor was part of that project.
    6sally6

    Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
     

    1/06/2025 4:33 PM  #9

    Raymond_B
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    Re: ACP radiator drain thread size?

    RTM wrote:

    Raymond_B wrote:

    I also meant to say, I ended up using Auto Cool Guy's copper inline sensor when I had that controller.

    https://www.autocoolguy.com/about

     
    I don't think I can use the inline adapter on my lower hose. There's not enough straight hose to place it.

    Sorry not the inline one, but the brass wrap around setup that goes over the radiator inlet.
     

     

    1/06/2025 4:35 PM  #10

    Raymond_B
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    Re: ACP radiator drain thread size?

    6sally6 wrote:

    Am I the only one who used a port in the intake ?!!
    I used a 160*sensor (I KNOW- I KNOW! ) from Summit. It screws right into a port in the rear-ish section of the intake.
    When the water gets 160*....fan comes on !
    I can't remember when it cuts off butt there are several on/off options available.
    My goal was to hide MOST of my wires under the hood.
    This sensor was part of that project.
    6sally6

    ACG will say he wants it in the lower hose as a more accurate way to measure cooling. I'll let the debating begin on that one
     

     

    1/06/2025 5:17 PM  #11

    RTM
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    From: Cape Coral FL
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    Re: ACP radiator drain thread size?

    Well I'm sure that could be an option to splice into the temp sensor in the intake.  I would like to add that I'm not sure if there's a difference in how the ACG sensor works compared to what the sensor is that came with my autometer gauge.   Second thing is if I was to splice into the intake sensor I would actually complicate my current wiring setup.  Keeping the temp sensor at or near the lower hose puts it within 12" of the fan controller.  The way I have the fan controller located has allowed me to reuse wires I no longer needed from going to a one wire alternator and it's the best spot I could really put the controller. To sum it up for me this is the simplest and by far the cleanest I can make this look. 

    I posted earlier because I was going to ask ACG specifically about what I had to make sure that what he sells would work in that location.  To answer my own question it's 1/4 NPT and he sells the temp sensor in that size.    Now I can place my order tomorrow and get closer to getting this 6 year build on the road.

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    1/06/2025 8:09 PM  #12

    MS
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    From: Canyon Lake, Texas
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    Re: ACP radiator drain thread size?

    I am not an electric fan guy, so I have a legit question, I think. Wouldn’t you want the temperature sensor at the top of the radiator where it reads the hot part of the system?  Or are you wanting to sense when it gets DOWN to a certain temperature?

    Inquiring minds want to know…

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    1/06/2025 8:32 PM  #13

    Rudi
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    Re: ACP radiator drain thread size?

    MS wrote:

    I am not an electric fan guy, so I have a legit question, I think. Wouldn’t you want the temperature sensor at the top of the radiator where it reads the hot part of the system?  Or are you wanting to sense when it gets DOWN to a certain temperature?

    Inquiring minds want to know…

     
    When I ran an electric fan that’s how I had it wired, I ended up going mechanical .

    Good work ain't cheap, Cheap work ain't good!   Simple Man
     

    1/06/2025 8:38 PM  #14

    Raymond_B
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    Re: ACP radiator drain thread size?

    MS wrote:

    I am not an electric fan guy, so I have a legit question, I think. Wouldn’t you want the temperature sensor at the top of the radiator where it reads the hot part of the system? Or are you wanting to sense when it gets DOWN to a certain temperature?

    Inquiring minds want to know…

    It looks like he redid his website, there used to be some info on there about why he wants to use the lower hose. I imagine it has something to do with measuring outflow temps vs inflow or maybe not on one side of the t-stat? Anyway, I do not know enough to expand any further

     

    1/06/2025 10:35 PM  #15

    6sally6
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    From: Surfside Beach,SC
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    Re: ACP radiator drain thread size?

    When running a street machine (true...a high performance street machine !) is it 'really' so critical to measure the outlet or the inlet temp ?!
    You just don't want it to run hot and not know it..right?
    You should have plenty of radiator-water pump-coolant in reserve that the exact location of the sensor is irrelevant !...Right ?
    I vote 'stick-that-puppy' where it's the most conveeenient ! (Roseanna-Rosanna-Danna)
    6s6

    Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
     

    1/07/2025 6:51 AM  #16

    RTM
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    From: Cape Coral FL
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    Re: ACP radiator drain thread size?

    Well I won't pretend to know what I'm talking about here when it comes to the best location for the temp probe but ACG does suggest the lower location.   It just seems right but I can't explain why.  Does it matter, I don't know.

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    1/07/2025 8:57 AM  #17

    BobE
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    From: White Plains, NY
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    Re: ACP radiator drain thread size?

    I am using an electric fan with the DCC controller.  DCC’s temp probe specified location is into the radiator fins at the lower portion of the radiator.  As ACG recommends a similar location for their fan controller, I’d go with that.
     
    My thoughts would be that the engine temperature gauge probe being mounted in the intake manifold will reflect the actual engine temperature.  A stuck closed thermostat would read high temperatures.  A stuck open thermostat would read cooler temperatures.  In either case, the fan would not really be doing anything.
    For control of an electric fan, I would think one would want it based on the actual temperature found in the radiator.
    Well, that's my thoughts. 

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

    1/07/2025 10:44 PM  #18

    Rufus68
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    Registered: 4/26/2017
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    Re: ACP radiator drain thread size?

    MS wrote:

    I am not an electric fan guy, so I have a legit question, I think. Wouldn’t you want the temperature sensor at the top of the radiator where it reads the hot part of the system? Or are you wanting to sense when it gets DOWN to a certain temperature?

    Inquiring minds want to know…

    The impact of putting the sensor at the outlet of the radiator instead of the inlet is to signal when the radiator requires more cooling airflow in order to drop the coolant temperature.  Say you're driving in a cold environment, the radiator will dissipate more heat without the need of enhanced airflow.  However, driving in a hot environment will require additional airflow sooner or more often.  This also would help identify when natural airflow from driving at speed does the cooling job without needing assistance from a fan.

    Bottom line, the outlet of the radiator takes into account the efficiency of the radiator working in the current conditions.
     

    Last edited by Rufus68 (1/07/2025 10:47 PM)

    1968 T-code Coupe with a 302.  Nice car, no show stopper for sure, but I like it.
     

     

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