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Mechanical Temp Gauge For 304

Discussion in 'Intermediate CJ-5/6/7/8' started by Ol Fogie, Jan 31, 2020.

  1. Jan 31, 2020
    Ol Fogie

    Ol Fogie 74 cj5 304, 1943 mb

    Jasper
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    [​IMG] The instrument cluster temp gauge on my 74 ,304 would not work when I started up the jeep after several years in storage. I had a new stewart warner mechanical temp gauge from another project. however the fitting on the capillary tube is way too large to fit the hole where the orginal electric sending unit was. The original electrical sender looks to be about 1/8 pipe thread and the analog tube looks to be maybe 3/8 pipe thread. The electric sender unit hole is so small even the bulb on the mechanical capillary won't even pass thru, so an adapter will not help. My question would there be somewhere else in the water jacket that have a larger access point? It seems all the mechanical gauges sold have the same larger fitting. ??:study:
     
  2. Jan 31, 2020
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

    Medford Mass USA
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    Does your thermostat housing have a place for a CTO? I suspect it does not. CTOs are 3/8" NPT and should fit your sender, maybe with a reducer. This one More Information for MOTORAD CH4018 is for a '90 Grand Wagoneer and will fit the 304 and give you an additional port.
     
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  3. Jan 31, 2020
    Ol Fogie

    Ol Fogie 74 cj5 304, 1943 mb

    Jasper
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    Thanks Tim, yes my engine does have a CTO in the thermostat housing. It also has another one in the top of the intake just to the right of the oil fill tube. both of them I removed and examined. they were both the same size and thread and large enough to accommodate the capillary tube fitting with the proper adapter fitting. The CTO's appeared to have some type of very fine thread and did not appear tapered like pipe threads although they had no copper gaskets or thread tape on them. When I reinstalled them they tightened down like a pipe thread. humm. It was getting late so I did not measure them. Think I will visit the FLAPS and see if I can get an adapter to fit, worst case I could find a fitting to fit the intake and drill and tap to fit my capillary tube nut. Will post some pic and maybe youall can help identify the thread. Thanks Jim
     
  4. Feb 9, 2020
    Ol Fogie

    Ol Fogie 74 cj5 304, 1943 mb

    Jasper
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    Well I finally made it to the FLAPS yestreday. Took all the parts with me, thermostat housing, cto valve, new temp gauge, the fitting/bushing that came with the new gauge ect. After much hum and humm and measuring at the FLAPS it appears the fitting on the new sw. gauge is about 16 mm with a pipe taper. Odd size fitting they were not familiar with. No way to adapt it to the 3/8 pipe thread where the cto in the thermostat housing was. The new gauge came with only one adapter/ bushing to connect this strange 16mm male fitting to a regular 1/2 in male pipe fitting. Trouble is I have no access hole any where on the engine with a 1/2 in pipe thread. Suggestions anyone?
     
    Last edited: Feb 9, 2020
  5. Feb 9, 2020
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

    Medford Mass USA
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    Can you post the brand and part number of the gauge you are trying to fit? It seems very unlikely that no one else with a US engine has dealt with this issue.

    [​IMG]
     
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  6. Feb 9, 2020
    Ol Fogie

    Ol Fogie 74 cj5 304, 1943 mb

    Jasper
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    This is the gauge I have. The large bushing you see is 1/2 inch NPT outside. and what I thought was a 3/8 NPT fitting threaded into it. When you remove the large bushing and try the 3/8 fitting in the cto opening (which I am sure is 3/8 NPT) of the thermostat housing it will thread in but it is an extremely sloppy fit. I am sure it would never tighten down enough to not leak before the threads would strip. However the small capillary tube nut appears to be at first look a 3/8 NPT. when measured it seems to be about .015 smaller than 3/8 NPT.
    BTW- the supplied bushing/adapter fits the tube nut perfectly with no slop in the threads.
    Stewart Warner Deluxe Series Gauges M-82326-60


    [​IMG]
     
  7. Feb 9, 2020
    Jeepsterjim

    Jeepsterjim Member

    Lincoln, CA
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    Could it be a different thread? Not NPT?
     
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  8. Feb 9, 2020
    Ol Fogie

    Ol Fogie 74 cj5 304, 1943 mb

    Jasper
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    I am beginning to think you may be correct. I have been out in the shop measuring that fitting. The guys at the FLAPS were calling it a pipe fitting, however I cannot detect any taper in the length of the threaded section at all. according to my measurements it is a 5/8 in.- 18 straight threaded fitting. :study: more research!
     
  9. Feb 9, 2020
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

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    From the picture, the adapter is tapered and definitely a NPT thread.

    I would go the the hardware store or HD/Lowes and buy a 1/8" NPT to 3/8" NPT bushing and compare it. You could even bring the gauge to the store and compare there, or try a bunch of fittings and see what is the same or compatible. I have found that "nominal" NPT varies a lot depending on the maker.

    The Summit page says that the probe is 1/8" NPT and the adapter is 3/8" NPT. Apparently this is wrong. The instructions say "Temperature probe comes with 1/2” NPTF fitting. Contact Stewart Warner distributor for additional adapter options." on the Stewart-Warner site. Who did you buy it from? This suggests that the probe thread is DIN or something, and you can get an adapter that will mate that to other NPT sizes.
     
    Last edited: Feb 9, 2020
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  10. Feb 9, 2020
    Ol Fogie

    Ol Fogie 74 cj5 304, 1943 mb

    Jasper
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    :bananatool::bananatool:AH, Just found this on the stewart warner web site. I would bet this would fix the problem.
    3/8 NPT Mechanical Temperature Gauge Adapter, Brass
    [​IMG]


    This fitting has male 3/8 NPT threads for universal installations. The other side has 5/8-18 female threads to accept a mechanical temperature gauge bulb. The female side also has the proper seat for Auto Meter and Stewart-Warner gauges. They are about 10 bucks. Think I will order one .
     
  11. Feb 9, 2020
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

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    Et voila. (y)
     
  12. Feb 9, 2020
    Ol Fogie

    Ol Fogie 74 cj5 304, 1943 mb

    Jasper
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    I hope that does the trick. will let youall know how it works out. Thank You so very much for your help, you guys are the greatest.
    Jim
     
  13. Feb 9, 2020
    bigjohn

    bigjohn Member

    Kelso Wa
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    Keep us posted. I'm considering installing one on my 304 for more exact temp monitoring , but already went through the same thing with my other 258 years ago. In that case I found another coolant port on the driver's side of the block.
     
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  14. Feb 10, 2020
    Ol Fogie

    Ol Fogie 74 cj5 304, 1943 mb

    Jasper
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    I ordered the fitting, will let you know how it works out. Should have it in a couple of days.
     
  15. Feb 12, 2020
    Ol Fogie

    Ol Fogie 74 cj5 304, 1943 mb

    Jasper
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    Well, I got the new fitting in the mail today, fixed the problem, fit perfect. the fitting is like the one in the pic above with 3/8 male NPT and the special 5/8 threaded female for the bulb nut. A regular brass bushing from the hardware store will not work because they do not have a machined seat for the bulb and nut. Also the bulb nut thread is not tapered pipe thread but straight threads. The photo below is showing the tube and bushing assembly installed in the rear of the thermostat housing where the CTO unit was. It was 3/8 NPT . IMG_0640.JPG
     
  16. Feb 12, 2020
    Ol Fogie

    Ol Fogie 74 cj5 304, 1943 mb

    Jasper
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    This is a pic of the other CTO located just to the right (pass side) of the oil fill tube in the intake minafold. Either this CTO opening or the one in the thermostat housing could be used as both are the 3/8 NPT. BTW most new temperature gauge kits sold should come with both the 3/8 and the 1/2 in adapters included, I guess the one I had only came with the 1/2 in adapter which would have worked on a F-134 cyl head. IMG_0518.JPG
     
  17. Feb 12, 2020
    algmmech

    algmmech New Member

    Montana
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    You really should put you temp gauge bulb in the intake in place of the CTO. Where it is now would only have the true temp when the thermostat opens.
     
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  18. Feb 13, 2020
    Ol Fogie

    Ol Fogie 74 cj5 304, 1943 mb

    Jasper
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    I agree, that is what I actually plan on doing. I just put it in the thermostat housing as a trial run to see that it was going to fit ok, I just happened to have that cto out at the time.
     

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