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1974 FJ40 running hot

Discussion in '40- & 55-Series Tech' started by RIDDLER, Jul 30, 2005.

  1. RIDDLER

    RIDDLER

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    Just drove the FJ40 after sitting for about three weeks. Started right up and did the standard warm up. Drove two miles residential and notices the temp gauge shot up fast. Pulled over. Coolant level is fine, oil level fine, radiator was warm but not so hot that my hand couldn't stand it for a second. Top of valve cover was also fine to touch for a few seconds.

    Does this sound like a thermostat stuck? This thing doesn't get driven much.

    thanks

    Aaron
     
  2. WES1977

    WES1977

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    Thermostat because you can touch and hold the upper part of the radiator. I would also drive some high way miles and see if it still over heats. If it does still overheat , almost certian thermostat. I've run in a pile of problems this month with my cooling system. I've changed the thermostat out, I've had to burp the system multiple times and changed out the fan clutch. What I screwed up was I filled the radiator with my cruiser pointing slightly on a down slop. I've found out on this web sit you need to burp your radiator with a up slop to get all the bubbles out with your rear heat on. Good luck. After all that I went to the beach today and was really impressed with my temp.
     
  3. nailbender

    nailbender

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    Thermostat is so cheap to replace I would try that but could also be the gauge. Is it the stock guage ?
     
  4. RIDDLER

    RIDDLER

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    yes

    Yes stock gauge.
     
  5. GreenFJ40

    GreenFJ40

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    My guess would be thermostat too, but while you're at it, get a new radiator cap too. Cooling systems require pressure (~13lbs if I remember correctly) to work efficiently. Whe I first bought my 40, it overheated on the test drive.. Rad cap was one of the reasons why.
     
  6. RIDDLER

    RIDDLER

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    thanks

    thanks guys. Work to start tonight on thermostat and cap.

    I can now put off the "resto" of the 1979 another week.

    Aaron
     
  7. IDave

    IDave

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    By the way, there are 170, 180, and 190 degree thermostats for the F engines. The 170s aren't generally available, except SOR has some used. For summer/trail running, I don' think thats a bad choice.
     
  8. RIDDLER

    RIDDLER

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    Not the thermostat

    OK I pulled the thermostat this evening. Put it in a pot with a meat thermometer, water above top of stat.

    the thermostat opened at 190F and closed at 180f. Is this odd? maybe the opening was slow and may have started at 180f?

    So I will replace this with Toyota OEM but I don't think it is the thermostat.

    A bit more background, this thing was running right in the middle of the temp. gauge around town two weeks ago when last driven. No coolant leaks at all.

    Radiator has never been "rotted" out that I can see from the records.

    Could this be the temperature sending unit? Where is this?

    thanks

    Aaron
     
  9. mallred

    mallred

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    Aaron, The temp sending unit is on top of the head on the manifold side.

    My truck is running about 10-15 deg hotter right now then normal with the hot weather. It hit about 210 deg today while climbing to 7500 feet and 90 deg outside air and lost no fluid.

    I ditched the stock temp gauge a long time ago and went with mechanical, you can use both stock and mechanical if you want just use another port on top of the head.

    Myrle
     
  10. tonkota

    tonkota

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    Aaron, if you need, I have some bungs for an after market head also. Stop by and get them if you need.
     
  11. dgangle

    dgangle total rice SILVER Star

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    Do you mean 'rodded' out or 'rotten' out?

    The OE-style radiators avail through various aftermarket sources are so inexpensive. If I were going to go through the hassle of having one rodded out I would just replace it and then you know the problem is not due to that part of the cooling system. A good mechaical guage is invaluable a swell in troubleshooting these problems too.
     
  12. petescoffee

    petescoffee

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    Could be the sending unit or the wire that attaches to it. You could install a mechanical guage.
    Do you have a fan shroud installed?
     
  13. Peter Fontaine

    Peter Fontaine

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    I hope 78 fj40 it's also running on the warm.. side. Had the radiator rodded out, new stant thermostat, added external oil cooler. Running at about 205 with Bosch mechanical gauge . Only thing I haven't done to go to replace the water pump. Anybody ever have issues with their water pump?