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Thread: Radiator plug thread size

  1. #1
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    Default Radiator plug thread size

    When I purchased my M400 it had a Ron Davis radiator, and last year it developed a slow leak. Tried to have it fixed locally but failed within a few months. Recently I purchased a noble radiator and I noticed the plug on top is different than the Ron Davis. Old radiator had a male AN fitting, because aftermarket, but my new OE radiator has a female thread designed for a plug instead of a cap. I bought an 1/8Ē NPT plug at the local hardware store but it only screws in like 2 threads, usually fittings like that will screw in at least 5 or more to get a good seal. So I began thinking perhaps itís BSP threads because itís a british car. Checked my build manual and canít find any details.

    Can anyone confirm the exact thread size for the plug on top of the radiator? Kind of anxious to drive my car again.

    Thanks,
    Andrew

  2. #2
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    Nobody? Does everyone else have the plug on the top passenger side of the radiator?

  3. #3

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    Quote Originally Posted by ashanson View Post
    Nobody? Does everyone else have the plug on the top passenger side of the radiator?
    My car came with a rad that lacked any bleeder on it. Not sure if that's how it came from the factory or if it's an aftermarket one.
    I bought a used rad from Willy which has the bleeder. But, if I pop it open I'm gonna have to go thru the entire process of rebleeding my system.

    BUT, I imagine it might be an ORB plug. maybe try a 1/8 ORB plug? Not sure if you have a hardware store that is more specialized (ie. not lowes/home depot), but you could check with them.

  4. #4
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    Thanks, also got a PM suggesting straight threads with an oring, I will try both metric and standard threads bolts by hand to see which is correct and report back, of course with an oring to seal, maybe some rtv for good luck haha.

  5. #5
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    I also asked around on the British forum and the basically unanimous response was 1/8” bspt. Had to order one to my local grainger supply and it appears to be correct. It’s slightly smaller than 1/8” npt, and threads in a good bit and gets tighter, that plus the ptfe tape should do the trick!

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