Bad Thermostat?

Discussion in 'The Big Chill' started by WayneNJ, Jun 16, 2022.

  1. WayneNJ

    WayneNJ Well-Known Member

    1971 Skylark 350. After running for a few minutes, the top rad hose is extremely hot and bloated. Bottom is warm. Bad thermostat? And what is correct thermostat temp. The buick manual is silent on this.
     
  2. TrunkMonkey

    TrunkMonkey Well-Known Member

    Factory was a 195F.

    But, over the years, scale, rust, radiator suffering from "solder bloom", erosion of water pimp impeller and other things can cause them to run hotter.

    You would be fine with a 180F. (use pan on stove and good thermometer to check opening start and full open position. It should start close to the open 180F for a 180F and fully open by 200F +- 5 degrees,

    Many cases of bad stats out of the box.

    Make sure the pressure cap is 14-16 lbs range, and the seal is good and pliable, the diaphragm is not cracked and the radiator opening is clean and proper sealing surface, and the "locking ramp and stops" are in good order nd not torn up.

    A good recovery tank is a must.

    You may have air trapped, and having a recovery tank 3/4 full after getting the car fully warmed, then letting it cool should pull a lot of coolant back into the system.

    This may take a few cycles, but almost always will work on a good system.

    When the T-stat opens, you should have good flow into the radiator, and it should not overflow, but be pulled back into the car. So you should only see flowing coolant.

    Do you have a shroud?
    What type of fan?
    Is is spaced within 1 inch of the back of the radiator and the blades half in half out of the shroud?
    And tips of the blade to the edge of the shroud?
    Belt tight enough? (not slipping) but not too tight or it will take out the water pump bearing.

    Also make sure timing is not retarded/vacuum advance is working, that can make an engine run very hot.
     
    Last edited: Jun 16, 2022
  3. WayneNJ

    WayneNJ Well-Known Member

    All things I will check. Thanks. Just bought car. Delivered from Chicago. I'm in Mobile Al. Pulled car off of carrier idled for a few minutes and hose was very hot. Car sat in storage for 20 years in NC. 56,000 miles on it.
    Many things to go through.
     
    TrunkMonkey likes this.
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    The system runs at a pressure of 15 psi. When you say bloated, do you mean it had a ballooned look? Sometimes damage to the inside of the hose can make it balloon. Change the hose if that is the case. The hose should be hot and feel firm. How hot? Use an infrared temperature gun, or put a gauge on it. I wouldn't suspect the thermostat, but I would suspect the radiator. They were undersized to begin with IMO.
     
    Smartin likes this.
  5. Max Damage

    Max Damage I'm working on it!

    That all sounds normal to me. But as suggested, check everything, make sure you have an accurate temp reading, a good radiator and good hoses.
     
  6. WayneNJ

    WayneNJ Well-Known Member

    Thanks for replies. I took a look again and ran the car and everything is normal. Just been awhile since I worked with an older car.
     
    TrunkMonkey likes this.
  7. TrunkMonkey

    TrunkMonkey Well-Known Member

    It's just like falling off a bike. No matter how long it's been you can still do it with your eyes closed and no hands.

    Nope. That's not right...
     
    Max Damage likes this.

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