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Hot Rods how do I Get rid of air trapped in cooling system.

Discussion in 'The Hokey Ass Message Board' started by rusty rocket, Jul 24, 2017.

  1. rusty rocket
    Joined: Oct 30, 2011
    Posts: 4,041

    rusty rocket

    So Ive had straight water in my sbc powered 32 while breaking in the new crate motor. I drained the water out and added antifreeze water mix and now I have an air lock. I ran the heater, squeezed the hoses, I took out a pipe plug near the t stat housing and added water until it was topped off. Ive done this three or our times and each time I add a small amount of coolant but it still has air trapped somewhere. Any ideas of anything else I can do? I have heard about drilling a small hole in the t stat.
    chryslerfan55 likes this.
  2. Truck64
    Joined: Oct 18, 2015
    Posts: 4,230

    from Ioway

    Find a steep hill or use a pair of floor jacks
  3. sunbeam
    Joined: Oct 22, 2010
    Posts: 5,026


    Pull the heater hose at the intake and fill until coolant starts coming out of the fitting and reconnect hose.
    dan c likes this.
  4. gotit
    Joined: Aug 27, 2009
    Posts: 360


    Slow down likes this.

  5. Budget36
    Joined: Nov 29, 2014
    Posts: 4,878


    This may or may not help you, but years ago it was time to change the coolant in my DD, reading up on it I found you couldn't just drain, and, I went to the dealer and watched them do it.

    They drained it, put a cap on it with a tube and a valve...operating, temp, open the valve...let the pressure out add coolant...repeat a few times.

    Next time it was due, I got a cap with the lever for the pressure release...seemed to work just fine.
  6. Mr48chev
    Joined: Dec 28, 2007
    Posts: 27,922


    My Ot daily has bleeders here, bleeders there and I'd have to look in the manual to remember how many and where.
    They aren't pretty but those plastic T's that they use in the heater hoses to power flush cooling systems work pretty good as system bleeders if the hose is higher than the rest of the cooling system. A small funnel and gentle pouring of coolant would let you top it off there too. Amazon link with Dorman numbers that are good about anywhere.
  7. bundoc bob
    Joined: Dec 31, 2015
    Posts: 125

    bundoc bob

    If you have a mityvac type vacuum pump you can devac the system. Make sure
    you don't get any liquids in it, or the seal will swell. Works on power steering systems,
  8. mcsfabrication
    Joined: Nov 26, 2006
    Posts: 887


    1/8" hole in the thermostat does the trick.
    alchemy, 6inarow, 1927graham and 2 others like this.
  9. A little confused here. First, you state the water was drained and antifreeze mix added and now there is an air lock. So how do you know you have an air lock? And how do you know there wasn't one during break in? Then after squeezing hoses and adding coolant to the intake, you still have an air lock. So I'm wondering if you have run the engine since adding coolant or not. I say until you run the engine and open the heater control valve, if you have one, then there is no way for the coolant to move through the system and push out the air.

    Once the engine is run as I have described, then top off the radiator. The radiator may overflow the next time the engine is run, but you will have a full coolant system even if the fluid level seems low.
  10. second generation LT1?
  11. Slow down
    Joined: Jan 7, 2014
    Posts: 94

    Slow down

    Morrisman likes this.
  12. 325w
    Joined: Feb 18, 2008
    Posts: 5,422


    Hole in tstat. Radiator pressure pump. Pump it up and walk away. Remove and add coolant.
    6inarow, Hudson31 and da34guy like this.
  13. Ralphies54
    Joined: Dec 18, 2009
    Posts: 732


    Jack the front up as far as possible and wait awhile,the air may work it's way out.
  14. rusty rocket
    Joined: Oct 30, 2011
    Posts: 4,041

    rusty rocket

    The break in didnt have air trapped because I have driven it about 450 mile with normal water temp. I drained water and replaced with antifreeze/water and it took lees than I put in the first time and the water temp climbs fast and hot(220) before I shut it down and ran a fan in front of it. Theres air trapped in the system.
    No its a g.m. 300hp 350.
  15. I say that perhaps the reason you put in less coolant after draining the water is because you didn't completely drain the system. You installed a new/rebuilt engine into the car, no coolant. Then drained the radiator? Block? There is a difference and there could be coolant in the heater core after draining the system.

    So in my mind I'm trying to think of "what is different" now from before you had problems. Thermostat still works?
    tb33anda3rd likes this.
  16. onetrickpony
    Joined: Sep 21, 2010
    Posts: 450

    from Texas

    Your issue might be related to this discussion:

    "Engines with thermostats don't allow any water to move in the front of the intake if you don't run a bypass. The water gets very hot in the heads during warm up and since the water is not moving, the heads just keep getting hotter and hotter until enough heat wicks up to the front of the intake/thermostat and allows it to open. Thermostats open and close during engine operation and what will happen is that the temperatures in the heads will swing wildly and not as well controlled as it will if you DO run a bypass. The internal bypass in the older blocks is only on one side because that is all you need to let the water move.

    I can tell you I have fixed MANY Vortech headed engines that have radical temp swings by adding a bypass to the front of the intake. It took me a while to figure out why that works but I know it has in more cases then I can count."
    Asphalt Angel likes this.
  17. It's fairly common to have some sort of air pocket after a coolant change (But usually it wouldn't displace as much as you seem to be saying??). And it's common for any air to work its way into the top of the radiator where you can check the level after the first half dozen cool downs and top off as needed. I always recommend a proper recovery tank system which will burp the air when hot and draw only coolant at cool down. Monitoring the level in the radiator and recovery tank can tell you a lot about what is going on in the cooling system.
  18. stated above, drill an 1/8th inch hole in the thermostat flange, problem with locked air...
  19. m&s rodz
    Joined: Jul 13, 2008
    Posts: 19

    m&s rodz
    from missouri

    Run it with the rad cap off or listen your temp sending unit until coolant comes out.

    Sent from my iPhone using H.A.M.B.
  20. 26hotrod
    Joined: Nov 28, 2009
    Posts: 918

    from landis n c

    What m&s rodz said is what I did and it worked for me...................
  21. This is true!
    I run Vortec heads -continuous temp fluctuation -until I added the external water by-pass. Your manifold likely has a provision for one. I run an Edelbrock intake-they have the plug in the front of the intake so you can plumb in a bypass to the water pump-made all the difference for me. Stock SBC Vortec motors have the external by-pass from the factory.
  22. southcross2631
    Joined: Jan 20, 2013
    Posts: 4,114


    It happened to me with my old Chevy powered gasser every time I drained the cooling system.
    Just had a restrictor instead of a thermostat and an electric water pump. I would jack the front end up
    as high as I could get it an turn on the pump. You could hear it when the air pocket burped and then you could fill it up and be done.
  23. rusty rocket
    Joined: Oct 30, 2011
    Posts: 4,041

    rusty rocket

    Thank you thank you thank you to all that chimed in, I did the 1/8th hole in the t stat trick and put the front wheels on the lift and raised it about 16'. It worked wonders.
    This is why the HAMB is so damn Kool. Information is plentiful for sure.
    Last edited: Jul 26, 2017
    6inarow likes this.
  24. 28 Ford PU
    Joined: Jan 9, 2015
    Posts: 447

    28 Ford PU
    from Upstate NY

    Yea ----- Then what? Let the jacks roll down hill to see which one is the fastest?

    Sent from my iPad using The H.A.M.B. mobile app
    Blues4U and Truck64 like this.
  25. Truck64
    Joined: Oct 18, 2015
    Posts: 4,230

    from Ioway

  26. Blues4U
    Joined: Oct 1, 2015
    Posts: 5,017

    from So Cal

    What is the radiator pressure pump going to do? It pressurizes the top tank of the radiator. What is connected to the top tank of the radiator (besides the radiator core)? The top radiator hose. Pressuring the top tank merely equalizes the pressure in the system. I dont see how that is going to force air out of the system.
  27. Budget36
    Joined: Nov 29, 2014
    Posts: 4,878


    Hmmn, seems he said said steep hill OR a pair of floor jacks, not steep hill AND a pair of floor jacks.

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