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QUESTION regarding "HOT" Water Temp

Discussion in 'The Hokey Ass Message Board' started by Jonnyhotrod, Jul 22, 2008.

  1. Jonnyhotrod
    Joined: Jul 27, 2003
    Posts: 430


    I'm almost to the point of registering the Model A. When running the motor (1964 Chrysler 413), the temp gage (vintage 12V SW that rests at 150 with the key off) peaks out to 240 degrees in no time; maybe a minute of run time or so. The timing is on and the mixture is close, but I don't run it long.

    I thought maybe I had some air in the system and flushed it through. No bubbles out the heater pipe on the water pump. It circulates with no thermostat, so the impeller seems ok. I swapped out thermostats (195 degree) and no change... In fact after over an hour driving to the store and back and installing the new t-stat, the gage still showed 240 before starting the car. The coolant from the water neck was piss warm. Before starting it again, I swapped out the gage for another one. I flicked over the key and it spiked as well.

    After running it for five minutes or so knowing it couldn't be THAT hot, the thermostat hadn't opened yet and I didn't want to take any chances, so I shut her down. I'm thinking maybe the sending unit which is about 2 years old on a motor thats run 2 dozen times is bunk. I'm buying a new one today which may be the solution, but if you have any other thoughts, please let me know.


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  2. yorgatron
    Joined: Jan 25, 2002
    Posts: 4,228

    Member Emeritus

    get the meat thermometer out of the kitchen drawer and check it,it's probably more acurate than the gauge/sender you have now...;)
  3. Searcher
    Joined: Jul 8, 2007
    Posts: 620


    If your replacing the sending unit it must be an electric gauge ?

    The sending unit needs to ground to the motor and the motor to the frame. If you seal it with teflon tape make sure enough threads are are exposed so it grounds, or try no tape at all.
    If the gauge moves or pulses with your blinkers or when you turn on the lights, it's probably the ground.

    240 is pretty hot, so you'd know it was that hot. Put your had on a valve cover or feel the dip stick. It wouldn't get to 240 as quick as your talking.

    Edit: Or you have the wrong sending unit for the gauge ?
    Last edited: Jul 22, 2008
  4. Jonnyhotrod
    Joined: Jul 27, 2003
    Posts: 430


    "Edit: Or you have the wrong sending unit for the gauge ?"- Searcher

    I don't know... It took the parts guy a half an hour to find the right sending unit for my block it the parts book. I told them I had a '64 413. He tried about 10 different part numbers and came up with "something that should work" at another store, which will be transferred locally tomorrow morning. It's a RB Chrysler like a 383/440 so I didn't think it would be that difficult, plus 413s were used in motor-homes, etc. so I assumed they'd have a bunch.

    As for working with the gage, I didn't know they were specific. It's a 12V SW from my collection of junk, so I assumed it would work with a 12V sender that fit my water pump. The other gage that pegged was a 12V out of a mid 60's International truck. Is there someplace to cross reference these things?

    I'll try the new sender tomorrow and see if there's any change.


  5. Searcher
    Joined: Jul 8, 2007
    Posts: 620


    I'm thinking the sender needs to be a match to the gauge ?

    Maybe a gauge guy here and say forsure ?
  6. BLAKE
    Joined: Aug 10, 2002
    Posts: 2,776


    I believe the sender has to match the gauge since they operate off of variable resistance - a specific resistance signal from the sender is interpreted as a certain temp on the gauge. I'd just run a mechanical gauge (cheap) for a good benchmark to see if you have a motor problem or not.
  7. I'm pretty sure a Stewart-Warner sender has to be used with a Stewart-Warner gauge.

    Get yourself a mechanical Stewart-Warner or other good quality mechanical gauge and use that.

    Candy thermometers are excellent to read actual coolant temp.
    Get your own and leave Sweeties in the house.

    With a cold engine, leave the radiator cap off, start the engine and let it come up to where your gauge says whatever.
    Stick the candy thermometers temp probe into the coolant and see what it says.

    My bet is that it's simply a mismatch between gauge and sender.
  8. propwash
    Joined: Jul 25, 2005
    Posts: 3,858

    from Las Vegas

    Geez....Stewart Warner gauges need to be used with S-W senders. You can put factory senders in all day long and never get an accurate reading with an aftermarket guage. I NEVER EVER EVER use electric temp guages. or OP gauges for that matter. I want to know exactly what's going on in both departments. Go to a REAL parts house for a mechanical water temp guage - I prefer SW, but there are several good ones out there. Most of your mail order speed merchants handle S-W, just go on line. I'll bet there's even a Hamb'r vendor on here that handles decent gauges.

    "never shake hands with a proctologist"

  9. Weasel
    Joined: Dec 30, 2007
    Posts: 6,693


    You could buy a Thermocap and put that on the radiator for an accurate reading. Make sure you order the right pressure - that way you should always get an accurate reading regardless of what the gauge says.
  10. kenagain
    Joined: Dec 15, 2005
    Posts: 820

    from so cal

    put a old 6 to 12 v resistor in the system wiring between the gage n sender look at reading on cold warm her up n see where it's at check with a thermometer in radiater n go from there lot more accurate then what you have now
  11. Yeah, I'd look at the sender, or as C9 say's, get yourself a mechanical gauge, then you don't have to worry about the sender not grounding.
  12. With an electrical gauge, the sender MUST be the correct one specified for the gauge, since the gauge is calibrated to suit the sender. Also, some senders work on increasing resistance, some on decreasing resistance.
  13. Mr T body
    Joined: Nov 2, 2005
    Posts: 2,196

    Mr T body
    Alliance Vendor
    from SoCal

    Chances are you need a 280EC 1/4" NPT
  14. tommy
    Joined: Mar 3, 2001
    Posts: 14,757

    Member Emeritus

    Boy does that bring back memories. My first engine swap was a 383 into a 58 Plymouth. I had the same problem using the 63 Chrysler sender to feed a 58 Ply. gauge. Same family right? I spent a lot of money chasing that wild goose. I put the Ply sender in the Chrysler engine and all was well.

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