Stage 1 overheated maybe bad fan clutch?

Discussion in 'Street/strip 400/430/455' started by green71stage1, Jul 14, 2019.

  1. green71stage1

    green71stage1 Well-Known Member

    Its been super hot in Florida lately and recently took the car for a 15 minute ride. I was stuck at 3 long lights and when I got home she was purging coolant into the reservoir. Car had been running fine ever since I had the engine rebuilt. Water pump is not leaking and is 1.5 years old. Radiator has no leaks. Its a custom built one. I'm thinking either a stuck thermostat or most likely my fan clutch is bad (its 20 years old) I am going to check the fan clutch this week. As the engine get hotter the clutch will get stiffer so it shouldn't free spin when hot... is that correct? Since its that old it should be replaced anyway. It there a high performance one or can someone please supply a GM part number so I get the correct one? My gauges don't work and want to put a set of nice ones in the car. I appreciate any help guys!
     
  2. Schurkey

    Schurkey Silver Level contributor

    Are you sure there's a problem? The cooling system is designed to blow coolant into the overflow bottle. That's how it works.

    If the overflow bottle is at the "Full Cold" mark before it's started, and doesn't get excessively full...it's fine.

    Drop a baking thermometer in the rad filler neck and idle the engine until fully warm, or point an infra-red temp gun at the thing and find out how hot it's getting.

    Lots of fan clutches get replaced because the radiator is rotted and won't heat the air. If the air around the fan clutch isn't hot enough, the clutch won't engage.
     
  3. Richie

    Richie Well-Known Member

    I had a car once ( not a Buick GS) that I could not figure out why it was overheating. It was a bad radiator cap. The last thing you would think to look at.
     
  4. Mark Demko

    Mark Demko Well-Known Member

    First thing, check the rad cap, factory is 15/16 lbs.
    If the spring on the cap is weak, it could be opening the rad to the overflow tank at 8,9,10 lbs or whatever, far less than the 15/16 lbs its suppose to hold back, giving the illusion of overheating
     
  5. LARRY70GS

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

    Lots of factors can cause high coolant temperatures, but you have no gauge so you have no idea what it is running at, and that makes it harder to diagnose as well. How old is the radiator? Do you have a shroud? What is the ignition timing at idle? The fan clutch should not freewheel especially when hot. With the engine off, give the fan a good spin. If it turns once or more, the clutch is bad.
     
  6. green71stage1

    green71stage1 Well-Known Member

    Thanks for all the comments guys. I will check the cap and clutch.
    Larry the radiator is 20 years old and probably 8 years ago I brought it to a radiator shop and they cleaned and pressure checked it. I do have a shroud and not sure of my ignition timing. I will have to borrow a friends to check that. Its been running fine so I really don't think the timing has changed. When the coolant backflowed into the reservoir it was boiling and steaming.
     
  7. 1973gs

    1973gs Well-Known Member

    Install a temperature gauge before you try to diagnose what may be a non existent problem.
     
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  8. DasRottweiler

    DasRottweiler -BuickAddict-

    Yes, temp guage or infared gun to check actual temps. I do think you might be on the right track with the fan clutch......Jim
     
  9. LARRY70GS

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

    If the radiator cap is holding pressure, it will elevate the boiling point of the coolant. The boiling point of water increases 3*/1psi, so a 15 psi cap will elevate the boiling point 45*. A 50/50 mix of water and A/F will boil at 223* at sea level, so a coolant mix will boil at 268*. Now if your cap is no good, it might be boiling into the overflow at 223* or so. If your cap is good, it means the coolant is a lot hotter than that. See why you need a gauge? You might be running around at high temperatures and you'll never know it until it reaches critical temps. The idiot light doesn't go on until 265* or so. In addition, a good gauge can let you diagnose a cooling problem. You can see when the thermostat opens with a gauge. You can also diagnose an air flow problem vs. a radiator problem with a good gauge. If it heats up in stop and go traffic, but cools down on the highway, suspect air flow or retarded ignition timing at low speeds. If it heats up on the highway the faster you go, suspect a radiator coolant flow problem. In my experience, there is no way to thoroughly clean a brass/copper radiator. There is a reaction between the solder used and coolant that forms a white crusty deposit that lines the tubes clogging the radiator, just google "radiator solder bloom". Relatively retarded ignition timing (below 10* BTDC) will cause an engine to heat up in stop and go traffic. If you run your vacuum advance to manifold vacuum, you'll get a 14-18* boost in timing at closed throttle. That can help a lot.
     
  10. Brett Slater

    Brett Slater Super Moderator Staff Member

    Dumb question: what happens if you drive around all day in 85 degree weather and the overflow level basically stays the same?
     
  11. Mark Demko

    Mark Demko Well-Known Member

    Its operating as it should:D
    The overflow/coolant recovery and the radiator are two separate systems UNTIL the spring on the cap opens the valve above whatever its rating is, and allows coolant to flow into the overflow reservoir.
     
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  12. Brett Slater

    Brett Slater Super Moderator Staff Member

    That's what I like to hear. :D

    What's funny is: I've noticed (at car shows/cruise nights) that seemingly none of the other makes/models built around the same time came with overflow reservoirs.

    Environmentally friendly they weren't.
     
  13. Schurkey

    Schurkey Silver Level contributor

    The same as WHAT? The same as when it's cold? The same as when it first warmed up to operating temperature? The same as the overflow tank on your wife's Nissan?
    Which should happen every time the engine warms up to operating temp. Maybe it happens several times as the engine is warming, and then again after a hard run and the coolant temperature rose a bit.

    The level in the overflow bottle should be lowest when the engine is coldest, and highest when the engine is hottest. The level in the overflow tank BETTER change with temperature or there's something wrong--the most common problem is low coolant level + an air leak. When the rad has air in it, it's relieving pressure by blowing air out--which doesn't raise the level of the overflow bottle. When the engine cools off, there'd have to be an air leak in the overflow hose or the rad cap, to allow air instead of coolant back into the radiator.

    The second most common cause is stretchy, worn-out radiator hoses that balloon excessively under pressure. The expanding hoses add coolant capacity, so the pressure rise is slower and more-even. The rad cap doesn't need to relieve pressure because the hoses have "absorbed" the expansion of coolant. (Until the hoses pop, and the coolant hits the pavement, and the engine stalls and won't re-start.)

    When the system works properly, the radiator will "breathe" coolant in and out of the bottle based on temperature changes, and the radiator will ALWAYS be FULL TO THE TOP.


    It's a dynamic system, and it's all based on radiator pressure--which is based on average coolant temperature throughout the entire system, and water pump pressure. If the rad cap is on the pressure (inlet) side of the radiator (common with vertical flow radiators) the cap is subject to coolant pressure PLUS water pump pressure. The big advantage of a cross-flow radiator is that the cap is on the suction (outlet) side of the rad, so it sees coolant pressure MINUS water pump pressure; so the suction of the water pump helps to keep the cap from "popping" and relieving pressure. The system therefore operates under higher pressure than the cap rating.

    If the proper coolant level was maintained in the rad, not much spilled onto the ground. The spillage happened when folks didn't leave an air space at the top of the rad for expansion. The rad cap would pop to relieve pressure, but only air would come out if the level was correct.

    Lots of "overflow kits" were sold in the '70s to guys that didn't have OEM overflow tanks. You'd get a generic plastic bottle with a plastic cap, hose, a few sheet-metal screws to mount it to the inner fender, and a rubber gasket to shove into the existing rad cap to turn it into a recovery-style cap.
     
    Last edited: Jul 16, 2019
  14. Brett Slater

    Brett Slater Super Moderator Staff Member

    I've noticed after cruising in the hot weather for a while, the overflow level definitely rises a little but overall, my car runs cool.

    The Harrison 3 core was cleaned and leak tested last year. Water pump/thermostat was replaced and I'm utilizing the factory shroud & 7 blade fan and clutch.

    I also check the coolant level in the radiator every other time out and it's always the same.
     
  15. LARRY70GS

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

    The whole purpose of the overflow is to store the over flow. Coolant expands when hot and moves into the overflow container. When the system cools, it is sucked back into the radiator. You should see a slight rise in the overflow cold to hot. There are markings on the overflow tank.
     
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  16. DasRottweiler

    DasRottweiler -BuickAddict-

    Where we at on this?
    I'm all about the closure...
    Gut a lil skin on weak fan clutch....Jim
     
  17. 1969RIVI

    1969RIVI Well-Known Member

    so what's going on if the level never changes in the overflow tank when the system is hot or cool?
     
  18. LARRY70GS

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

    I would suspect the radiator cap. My first question would be, Are you sure the level isn't changing at all?
     
  19. 1969RIVI

    1969RIVI Well-Known Member

    Sorry not to hijack the thread, just asking another valid heating/cooling issue question. My rad and cap are new (just a year old) and from what I can tell the overflow jug always has the same amount of fluid in it hot or cold? My temps usually sit between 190-205, sometimes it will spike up to 210-215 at a stop light but it never runs cooler than 195. I have a 180 hi flow T-stat in it.
     
  20. LARRY70GS

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

    That says to me that your cooling system has LOST control of the engine coolant temperature. A 180 stat is fully open at 200*. Beyond that, it can flow anymore coolant. You should never see more than 190*

    I know my engine seems to be an exception. I have a 19 year old Griffin radiator with 2 rows of 1 1/4" tubes. Aluminum heads and intake, 180* stat. Timing is locked at 34* with my vacuum advance delivering another 10*. Stock fan shroud, clutch, and 7 blade 18" fan, 50/50 coolant mix with 1 bottle of water wetter.

    Yesterday, I took a 90 mile round trip out on Long Island. Got stuck in stop and go traffic on the Long Island Expressway for the beginning of my trip out, and the end of my trip coming back. Ambient temperature was 95*. I can't envision a more extreme test for any cooling system. My Autometer mechanical gauge NEVER read higher than 185*.
     

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