72 Skylark 350 over heating

Discussion in 'Small Block Tech' started by 72skylarkconvt, May 5, 2019.

  1. 72skylarkconvt

    72skylarkconvt Well-Known Member

    I have had the the car for a few months not. Have driven around a little in colder weather no over heating.
    Today it was about 75. Took car on longer drive on HWY for about 3 miles then stopped. Picked up kid and came out and the car was pissing rad fluid out the over flow tank drip hose. No other leaks anywhere but I could hear the over flow tank gurgling some and in the radiator. I let it cool. Got back in drove another 4 miles or so, saw steam at red light so pulled off and same result. So had it flat bed tow back home. HOT light never came on though it does when you start it then goes off as it should.
    Water pump seems to be fine. No noises from it, not seized. No leaks anywhere in the system. Is this just a classic sign of the tstat going bad?
     
  2. 72skylarkconvt

    72skylarkconvt Well-Known Member

    I dought this is the issue but it has a small hissing leak. Is on a heater core line. Could this be causing any issues short of the hiss leak that makes this needing replaced. What is it called, where can I buy one?
     

    Attached Files:

  3. hwprouty

    hwprouty Platinum Level Contributor

    Is it low on coolant?
     
  4. LARRY70GS

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

    There are all kinds of things that can make an engine run hot. Leaks are not good, you need to fix any leaks and make sure the radiator is full, not the overflow, the radiator. With a leak, the radiator level can go down leaving the overflow with coolant in it. Also realize that if you hear a hiss, the system cannot operate under pressure as it should. That will make it boil over as well. It would be good to actually know how hot it gets. Install a real gauge. How old is the radiator? Where is your ignition timing? Does the mechanical and vacuum advance work? Fan and shroud intact?
     
    Last edited: May 5, 2019
    GS464 likes this.
  5. 72skylarkconvt

    72skylarkconvt Well-Known Member

    The motor is completely all orig. Nothing has been taken off of it from factory literally. There have been no leaks since I have had the car. Today when I first saw it I walked out to the car and saw the rad fluid under it on pass side. Is was ONLY coming from the hose that drains the overflow/resivoir tank on pass side near battery. I checked everything, no leaks from any hoses, nothing at all from WP. It was all dry. It was just over heating and pushing it all out the over tank. Nothing was coming from the rad. Last few rides, checks of coolant system rad was full at cold pre start up, the overflow tank was filled to correct level.
    I check all that stuff cause I know car is old, not driven much but driven.
    Fan and shroud all in place. Car runs fine, was running fine when it was heating up, seems like it is in good time. Could this be as simple as a Tstat just bit the dust?
    The second time I shut it off for the tow, I had time to sit for the tow, rad was half empty, resivior/overflow was empty. Rad fluid was nice and green, I don't feel the radiator is the issues, no sludge in it. Water pump making zero noise, not siezed, can't think that is the issue. If it were a head gasket I always thought that would heat the motor up pretty much with in minutes. Like I said I have driven this car on 5 to 15 min runs with no issues, today, well, not.
     
  6. 72skylarkconvt

    72skylarkconvt Well-Known Member

    No hesitation when driving it what it was clearly heating up.
    Does anyone know what the device is in the pic I attached before. It does have a hiss coing from it, there is a small pin tip hole in it, you can see it sweating fluid. It is on a heater core line into the top of the intake left of Tstat. I assume it just cuts off flow to core?
     
  7. alec296

    alec296 i need another buick

    Replace the heater hose , get a new thermostat. Check timing, maybe add 2 degrees over stock. Check points. Get a new radiator cap. Then drive again.
     
  8. hwprouty

    hwprouty Platinum Level Contributor

    Did you fill the radiator back up and test drive it? A small leak can make a big difference over time, and once it's low. Well you overheat!
    I wasn't aware Skylarks used a water valve in the heater hose, neither of mine have one, although mine are Non-AC. That may be the difference!
     
  9. 72skylarkconvt

    72skylarkconvt Well-Known Member

    Yea just figured out the the AC cars like mine do use the water heater control valve. I did not check the car today but do check fluids just because the car is old from time to time. I will replace the rad cap, top it all off and see what it does. Just odd the HOT light never came on. It does when you first start the car so that would tell me the temp device would be working???
     
  10. hwprouty

    hwprouty Platinum Level Contributor

    There's a reason those lights are called 'Idiot Lights'! They are not really that accurate!
    I'd be willing to bet after you top'er off and give it a go it'll be fine!
    Although replace that water control valve for sure!
     
  11. gstewart

    gstewart Well-Known Member

    flush the block & the radiator, also.
    U would be surprised at the crap that is expelled from a block flush. Been there; done that..
     
    GS464 likes this.
  12. 1987Regal

    1987Regal Well-Known Member

    it's a heater valve that controls flow to heater core.
    https://www.rockauto.com/en/catalog...028,heat+&+air+conditioning,heater+valve,6860

    If it were me I would replace it it could be your leak/problem it would be no different then a small hole in a radiator hose once it's under pressure it's got to go somewhere it's being forced out, does it look like it's leaking there? And once your radiator runs low on coolant it's going to overheat.
     
    Last edited: May 6, 2019
  13. 72skylarkconvt

    72skylarkconvt Well-Known Member

    What pound rating should my rad cap be? I assume stock Tstat is 190, 195? Can I run a lower one like a 180, would that be beneficial in my stock car/motor with just weekend driving.
     
  14. LARRY70GS

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

    OK, this car is all original so I am not surprised that it runs hot right on the edge of overheating is pretty normal for this engine. BTW, if the radiator is truly 47 years old, there is no way that it is not at least partially clogged:). Because of emissions, Buick set this engine up with retarded ignition timing and no vacuum advance until 3rd gear. It’s a wonder they all didn’t overheat all the time. Pretty easy to fix all of that.
     
  15. LARRY70GS

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

    15 psi is stock, 16 psi is fine. Yes, run a 180 stat for sure.
     
  16. 72skylarkconvt

    72skylarkconvt Well-Known Member

    Thanks. Seeing conflicting gaskets info. If I have to do the tstat, is that housing have a 2 or 3 hole gasket. Looks like 3 to me but Year one is showing me a 2????
     
  17. LARRY70GS

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

    How do you know the car is all stock? Have you owned it since new? If not, you can’t be sure. Looks mean nothing. 47 year old cars have parts changed over their lifetime.
     
  18. 72skylarkconvt

    72skylarkconvt Well-Known Member

    while I have you all, a little off topic but is there a site to decode my cowl tag?
     
  19. LARRY70GS

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

    Forget Year One unless you wan’t to pay more. Any parts store will have what you need. Or www.rockauto.com
     
  20. 72skylarkconvt

    72skylarkconvt Well-Known Member

    Car has been in same family since (brother then sister) 1982 till I got it. Pretty good bet it is orig, they never did anything but keep it fixed when something was leaking or the top needed replaced, etc. Hell it is still rocking the old 2 barrel.
     

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