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How to check thermostat

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Ray-F250, Aug 18, 2019.

  1. Ray-F250

    Ray-F250 Registered User

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    hey fellas how to I check to make sure my thermostat is opening when it’s supposed
     
  2. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Boil it in a pot and measure the temp it opens
     
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  3. Ray-F250

    Ray-F250 Registered User

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    10/4 so there’s not away to check with out taking it out ?
     
  4. chillman88

    chillman88 Supporting Member Supporting Member

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    You should be able to get idea if you monitor it with an infrared thermometer but I'm not sure how well that will work.
     
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  5. Macrobb

    Macrobb Full Access Member

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    Put a temp gauge on the engine, an actual aftermarket gauge. If the thermostat is working, temps will climb until 195 or so, then either stay right there or drop a few degrees, and stay right in the 180-195 range(unloaded, not towing a trailer). If you see higher temps than that just driving around, you may have a problem.
     
  6. Cubey

    Cubey Full Access Member

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    Yep, my F250 runs around 180-190 at highway speeds. I have seen it climb to 200F when gunning it to get it up to speed when merging on to the freeway but it drops once the RPMs drop to normal. Even when towing a 27ft (but not very tall) travel trailer, it stayed under 200 generally.

    I have yet to get my RV up to highway speed since I put a gauge on it. I will on Wednesday afternoon finally, since I'm going to be on my way south for the winter. I expect it'll run a bit warmer considering it's massive vs the F250. I am planning to replace the thermostat simply as a preventive measure since it's probably running the original. Gonna do it at the same time as the seemingly weak, but spinning full time, fan clutch.
     
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  7. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    Be aware that the t stat can get "tired" and not open all the way anymore. I boiled my old one with my new motorcraft and they would open about the same time but the old one only opened half as far. This was adequate for empty driving but would it would over heat with a load.
     
  8. Hydro-idi

    Hydro-idi Full Access Member

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    If you have any doubts, I would just replace it with an OEM unit. They aren’t all that expensive, and probably one of the most important gizmos on these engines. An aftermarket t-stat will not flow enough to properly cool these engines FYI.
     
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  9. Cubey

    Cubey Full Access Member

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    That's what I've read, and it's why I am eager to replace it. I have 45 miles minimum to drive to get the new Motorcraft thermostat. I couldn't get Walmart or Amazon to ship one to a PO Box for some stupid reason.

    The next is a town about 10 miles away along the way so if I don't like what the real temp gauge is showing by then, I could always stop and remove the thermostat entirely (after it cools down again, after however many hours it takes) until I can get another 35 miles down the road to get the new one.

    I will be on a back highway where I can stay at 55 and it'll only be 78F max that day and not too windy, so that might help. If it looks like it's running too warm, I will go ahead and replace it in that city. The biggest hassle to me is draining coolant and repeated top offs as it burps out the air. Everything else is easy.

    I don't have a new gasket on hand, so pulling it here is a bad idea, unless I was sure it was overheating, and I'd have to use RTV only. Total removal is for emergency purposes only, of which it's not one (yet) I don't think. I'll know for sure one way or the other Wednesday afternoon, now that I have a real temp gauge. I might just take the hour or more to do it at the Walmart there so I can lay that worry to rest if I don't like the temperatures I'm seeing.
     

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