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  1. #1
    FEP Super Member erratic50's Avatar
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    Default Engine coolant system - getting the air out

    For years and years whenever I’ve opened a fox coolant system I’ve always jacked the car up as high as I could in the front and ran the engine until the thermostat opens and dumped 50/50 in while the engine is running about 2500-3000 then put the cap on.

    Then today I was thinking about my Grandpa’s old Galaxie 500 that nobody could ever seem to get the air out of the cooling system on. Not even with the jack the land yatch to the moon trick— the wheel base was just so damn long.

    Grandpa got mad one morning when it had been overheating the night before and took the temp gauge pickup out while the engine was cold and used a funnel to dump 50/50 in until it wouldn’t take anymore..... problem solved.

    Then I started thinking about the Chrysler Sebring I had where the shop procedure was to loosen the plug up on the top of the thermostat housing and run it until coolant comes out the tighten it back up.

    with that in mind...... they make thermostat necks for smallblock Fords that are drilled and tapped for a 1/8” NPT thermal sensor designed for electric fans.

    So, I think that I along with a few others in the world have been working to entirely too hard in multiple ways.

    1) you can dump 50/50 in the gauge pickup bung when the engine is cold and off. This will displace the air which will evacuate the thermostat area immediately.
    2) you can loosen the gauge pickup and let the air out with the engine idling then tighten it back down
    3) if you have it apart anyway the thermostat neck with thermal sensor bung is only $25 and comes with a NPT plug already installed

    Just my thoughts
    -- James

    Favorite thing I’ve said that’s been requoted: “"40 year old beercan on wheels with too much motor"

    My four eyed foxes:
    "Trigger" - 86 Mustang GT - Black with red interior. 5.0 T5 built as Z. Original motor ~1/2 million miles. 18 yr daily, 10 a toy
    "Silver" - 85 Mustang Saleen 1985-006? (Lol) Rare 1E silver GT / charcoal interior. The car is a little bit of a mystery. Current project bought as a roller, tons of Saleen / Racecraft pedigree

    Also in the stable - my son’s car. 1986 Mustang GT Convertible. Black/Black/Black conversion. 93 leather. VM1 ECU. T5Z

    past foxes -
    1989 Mustang LX Sport 5.0 AOD white/tan black top. Once I ran this one down I caught a wife.
    Wife also had a 1987 Thunderbird Turbo Coupe in the 90's.

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  2. #2
    FEP Power Member Ourobos's Avatar
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    You should try a 32v, Marauder, Cobra etc. Similar technique as the Galaxy.

    Seems overkill to me. With the front end up at and angle, even on a steep driveway, the heat on full blast - simply fill it up. Wait for the thermostat to open and then fill it the rest of the way. I put a quart or so in the overflow so it can suck it up if needed. Never had any issues, even on 600+ HP race cars. BUT - whatever works for you is all that matters
    1986 CHP SSP Coupe

  3. #3

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    Filled dozens and dozens of Fox 5.0s, SN95 5.0s and DOHC 4.6 Cobras, 2V GTs etc. Never raised one up in the air and never had any issues. Definitely knocking on wood I suppose if it happens that often to others. I always Fill up the radiator (car sitting on level ground) with the engine off to the top, start it up with the heat on high until the T-stat opens and then top it off. I guess I should feel lucky. I have heard of people having issues with the DOHC 4.6 but I have never heard of anyone with an air-locked 5.0 before. The DOHC 4.6 has that fitting in the crossover hose that you are supposed to remove to let air out.
    Last edited by homer302; 06-16-2018 at 07:06 PM.

  4. #4
    FEP Power Member vintageracer's Avatar
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    I have always filled the cooling system when doing a coolant change through the upper heater hose connection on the top of the intake or top of water pump. It's the highest point in the system. Adding your coolant from this location back fills the cooling system from the block through the heater core to the radiator which evacuates all air from the opened system.

    The radiator cap opening in the radiator is for topping off the system!
    Mike
    Remember, "Drive Fast, Turn Heads, Break Hearts!"

    1995 Ford Powerstroke F350 "Centurion" STRETCHED Crew Cab Dually

    I like "Cut & Coach Built" vehicles!

    www.musclecardeals.com


  5. #5

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    Quote Originally Posted by vintageracer View Post

    The radiator cap opening in the radiator is for topping off the system!
    The coolant overflow reservoir is for topping off the system in nearly every car made. most cars don't even have a radiator cap now.

    I have the red OEM Ford service manual for the Mustang and section 03-03-25 says:

    Fill the cooling system as follows:
    A. Fill radiator until coolant level reaches radiator neck
    B. Operate engine until water thermostat opens
    C. Stop engine and refill radiator and overflow reservoir
    D. Install radiator cap.
    Last edited by homer302; 06-16-2018 at 07:42 PM.

  6. #6
    FEP Power Member vintageracer's Avatar
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    I still use the radiator cap hole.
    Mike
    Remember, "Drive Fast, Turn Heads, Break Hearts!"

    1995 Ford Powerstroke F350 "Centurion" STRETCHED Crew Cab Dually

    I like "Cut & Coach Built" vehicles!

    www.musclecardeals.com


  7. #7

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    Quote Originally Posted by Ourobos View Post
    Seems overkill to me. With the front end up at and angle, even on a steep driveway, the heat on full blast - simply fill it up. Wait for the thermostat to open and then fill it the rest of the way. I put a quart or so in the overflow so it can suck it up if needed. Never had any issues, even on 600+ HP race cars. BUT - whatever works for you is all that matters
    This. Get it up to temp, and when it cools the motor will pull fluid from the overflow jug.

    Jess
    Previously owned;
    1979 Mustang, v6 swapped to EFI 393, custom installed m122 blower, 4r70w trans, Megasquirt II, T-top swaped in.
    1990 Mustang, 545 BBF, C-4 with brake, ladder bars.
    1983 Mustang, 1984 SVO Mustang
    1984 Mustang convertible, v6 swapped to 351
    1986 Mustang GT, 1989 Mustang GT convertible
    1992 Mustang coupe, 4 swapped to 302

  8. #8
    FEP Senior Member Matt J's Avatar
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    Most good new thermostats have a weeper hole at the top to allow the air bubbles, if there are any, to seep by the thermostat and up the return hose into the radiator. As long as the overfill tank is properly filled, the vacuum caused by the cooling liquid will pull in whatever it needs and any remaining air should go past the thermostat. It seems to work well with the 302 in these cars, though I can't speak for other makes.

  9. #9
    FEP Power Member Broncojunkie's Avatar
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    Quote Originally Posted by Matt J View Post
    Most good new thermostats have a weeper hole at the top to allow the air bubbles, if there are any, to seep by the thermostat and up the return hose into the radiator. As long as the overfill tank is properly filled, the vacuum caused by the cooling liquid will pull in whatever it needs and any remaining air should go past the thermostat. It seems to work well with the 302 in these cars, though I can't speak for other makes.
    This is exactly how I do it. Top it off and run it. I'll go back and top off the overflow tank after it cools down. Usually have to do that a couple times. I also really like the Flush & fill kits where you install a T fitting into the heater hose. It allows you to back-flush the system easily and gives you a great place to fill it.

  10. #10

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    Quote Originally Posted by Matt J View Post
    Most good new thermostats have a weeper hole at the top to allow the air bubbles, if there are any, to seep by the thermostat and up the return hose into the radiator. As long as the overfill tank is properly filled, the vacuum caused by the cooling liquid will pull in whatever it needs and any remaining air should go past the thermostat. It seems to work well with the 302 in these cars, though I can't speak for other makes.
    Good point, I drill a 1/8" hole in the thermostat for this purpose.

    Jess
    Previously owned;
    1979 Mustang, v6 swapped to EFI 393, custom installed m122 blower, 4r70w trans, Megasquirt II, T-top swaped in.
    1990 Mustang, 545 BBF, C-4 with brake, ladder bars.
    1983 Mustang, 1984 SVO Mustang
    1984 Mustang convertible, v6 swapped to 351
    1986 Mustang GT, 1989 Mustang GT convertible
    1992 Mustang coupe, 4 swapped to 302

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