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temp DROPPING in 350 SBC 1953 Chevy?

Discussion in 'The Hokey Ass Message Board' started by atomickustom, Jul 11, 2012.

  1. atomickustom
    Joined: Aug 30, 2005
    Posts: 3,218

    atomickustom
    Member

    Okay here's a new problem I've never heard of: this morning on the way to work (temp in high 80s), while sitting at a red light the temp gauge in my '53 Chevy started going DOWN.
    Generally it'll go down the road all day long at 190 degrees no matter what the weather, and when it's close to 100 out the temp will very slowly creep up at a red light with the A/C on, but today the temp went from 180 to maybe 160 just in the half-mile from the traffic light to my workplace. I was running late or I'd have driven around longer just to see what would happen.

    Any idea what is up with that?

    My thoughts are: failing gauge, failing sending unit, or failing thermostat but I've never had a thermostat stick OPEN??

    I won't really know what's up until I drive home at 5:00 today but if something is getting hinky I'd like to figure it sooner than later.
     
  2. porknbeaner
    Joined: Sep 12, 2003
    Posts: 41,063

    porknbeaner
    Member

    Well they do stick open, I got on in the garage that is stuck open, the spring also breaks on occaision.

    But there are a lot of variables here, start with the simple stuff and work your way out.

    For instance, you can turn the switch on and pull the wire off your sender then ground it. if it goes to hot you can rule out the temp gauge.
     
  3. Rex_A_Lott
    Joined: Feb 5, 2007
    Posts: 964

    Rex_A_Lott
    ALLIANCE MEMBER

    Make sure its not out of water! I've seen the gauge go down when a hose busts or something, the gauge wont read right if its not covered in water.
     
  4. Yes, they do stick open. I had one in a daily do that - first it stuck closed, then it opened and stayed and I never noticed until a few months later when it got cold enough I wanted some heat - and had no heat. The temporary cure was some cardboard in front of the radiator; you might be able to try that and see if the temp comes up.

    Sometimes the temp sender can go bad, too - some Chevy engines have the thing on the left side front on the head, if the wire dangles and touches a manifold it can melt and screw it up. That's probably unlikely on your car but worth mentioning.
     
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  5. atomickustom
    Joined: Aug 30, 2005
    Posts: 3,218

    atomickustom
    Member

    Well that's two things I can do before I even leave the parking lot. Thanks, guys!
    I'm pretty sure it's not out of water (no obvious leaks, and the upper hose was hot like normal) but it'll be easy enough to find out when I walk out to the car.

    If a thermostat can fail in the open position then that is my guess. That'll be pretty easy to diagnose, too. I've only had them stick closed - this is much better in my opinion!

    Any brand recommendations if I do end up replacing the thermostat? I've got NAPA, Autozone, and O'Reilly all within a couple miles of my house. (Last time I bought a "name brand" thermostat it turned out to be made in CHINA!)
     
  6. Odds are they're all made in China, but you might start with Napa and just look at it before buying.
     
  7. Rex_A_Lott
    Joined: Feb 5, 2007
    Posts: 964

    Rex_A_Lott
    ALLIANCE MEMBER

    I used to like Stant...but the last one I bought was made in Mexico
     
  8. nutajunka
    Joined: Jan 24, 2007
    Posts: 1,466

    nutajunka
    Member
    from North Indy

    I don't know how true what I was told is, but the last one I bought the counter person told me that they are made to stick open when they fail verus sticking shut nowadays......:confused:
     
  9. tommy
    Joined: Mar 3, 2001
    Posts: 14,758

    tommy
    Member Emeritus

    Buy a cheap infrared remote temp tester or borrow one before you go too far. It could be just a failing sending unit or gauge. A thermometer in the radiator neck may give you a clue to it's accuracy.
     
  10. atomickustom
    Joined: Aug 30, 2005
    Posts: 3,218

    atomickustom
    Member

    Gauge checked out fine (thanks, porknbeaner). Plenty of coolant (thanks). Gotta be the thermostat because I drove home in 95 degree heat and it all worked just the way it was supposed to. Oddly, that includes the thermostat. I am guessing that once the car cooled down it snapped shut. But I'm still going to replace it - it's cheap insurance and I don't trust it anymore.

    Thanks, everyone!
     

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