4.9 coolant flush and fill procedure!
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HT4100 4.1, 4.5, 4.9 Discussion, 4.9 coolant flush and fill procedure! in Cadillac Engine Technical Discussion; I need to do a coolant flush and fill soon. i searched every forum in here and everything was on ...
  1. #1
    92EldoTC's Avatar
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    4.9 coolant flush and fill procedure!

    I need to do a coolant flush and fill soon.
    i searched every forum in here and everything was on the N* system.
    I need to know:
    1. is there a drain plug on a 4.9's radiator?
    2. would green coolant be better than orange, or does it matter what kind (Dexcool or green) is poured down the radiator.
    3.How many gallon containers of coolant would I need to pour down the radiator for the system to have adequate coolant in it>
    4. of course distilled water would be used, would this be the same amount used as coolant for a 50/50 mix.
    5. how many pellets or tubes of Bars should I put in the radiator?
    thanks for the answers!

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    thu's Avatar
    thu
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    Re: 4.9 coolant flush and fill procedure!

    1. The drain plug of the 4.9 is on the driver's side of the radiator, at the bottom. The valve 'handle' is on the back side (toward the back of the car) of the radiator. The spout where the coolant shoots out is at the very bottom. You may have to crawl underneath to see it.

    2. If it was already filled with the green stuff, stick with the green stuff. Don't switch. I don't think the '92 Eldo 4.9 came from the factory with Dexcool in it.

    3. That depends on your car, but my 93 Deville's cooling system has 12.1 quarts of capacity. Refer to your owner's manual.

    4. Yes

    5. The FSM for my 93 Deville says 6 tablets of engine coolant supplement (sealant), GM Part Number 3634621. You can get it at your GM dealer. It's really inexpensive. Perhaps others on this forum have better information.

  4. #3
    HUF's Avatar
    HUF
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    Re: 4.9 coolant flush and fill procedure!

    Bar's Leaks Golden Seal powder for $1.44 at Wal-Mart is the same stuff. I put two tubes.

  5. #4
    behind-bars is offline Cadillac Owners Connoisseur
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    Re: 4.9 coolant flush and fill procedure!

    Just refrencing something I read somewhere, But with the filler neck on the 4.9L radiator wouldnt it be possible to just use a siphon and suck the coolant out of the neck? If so do you think it would still be necessary to use the drain plug?

  6. #5
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    Re: 4.9 coolant flush and fill procedure!

    Why the heck would you want to siphon it out? It's soooo easy using the normal drain.

  7. #6
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    Re: 4.9 coolant flush and fill procedure!

    Quote Originally Posted by behind-bars View Post
    Just refrencing something I read somewhere, But with the filler neck on the 4.9L radiator wouldnt it be possible to just use a siphon and suck the coolant out of the neck? If so do you think it would still be necessary to use the drain plug?
    I only siphon, and do that every year. No mess and takes ten minutes. Some have problem reaching for the drain plug. I am pretty sure I can siphon the same volume others drain ( about1.5 gal).

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    Re: 4.9 coolant flush and fill procedure!

    ok, so im guessing that the valve controls the flow of coolant coming out, right?
    are the spout and the drain plug the same thing or are they in different locations from eachother?
    thanks

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    Re: 4.9 coolant flush and fill procedure!

    It's just like a spigot. Turn the knob and out comes the coolant from the spout.

    When we say 'drain plug', we mean the one and only radiator drain. There's a little knob/valve just above it. Works just like a spigot.

    Crawl underneath and take a look. Or, grab a light and see if you can peer down the left tank of the radiator at the very bottom and eyeball it. You might have to stick your hand down there (wait until car cools off) and feel around.

  10. #9
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    Re: 4.9 coolant flush and fill procedure!

    i saw the drain plug but i couldnt see a valve handle.
    im going to unscrew the drain and let the coolant pour out.
    i saw something on the passenger side on the back of the radiator that sort of looked like a valve control but wasnt sure.
    i'll just use the plug to drain the coolant anyway. will this get most or all the coolant out without having to disconnect the lower hose?
    thanks so much!

  11. #10
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    Re: 4.9 coolant flush and fill procedure!

    That drain plug on the radiator is all you need to drain. It's the lowest point anyways.

  12. #11
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    Re: 4.9 coolant flush and fill procedure!

    Ok.
    Well i did the job using just the plug at the bottom. It was a lot less messy than draining my old camaro.
    I drained what i could using the plug.
    I closed the drain back up, filled with one half gallon coolant and one half gallon water. A
    fter that I put in the cooling supplement tablets. My radiator only took one gallon total mix to fill. Im guessing about 50% of the old stuff was still in there.
    I topped it off after letting the engine run for about 10 minutes, with the heater on full blast.
    While the engine was running, i left the radiator cap off and watched the coolant rise as the engine got hot. I noticed green coolant start emerging in the filler neck, the old stuff. When it got to the top of the filler neck I shut the engine off. Im guessing at this point all the air is out of the system.
    I filled the overflow tank to the engine hot mark.
    Also, since there is no Walmart where i live I couldn't get the Bar's Leak Golden Seal powder. I checked 3 parts stores, (Kragen, Napa, Autozone) and none of them had it either. What I did get from Kragen was 2 Gallons of Texaco Dex-cool. It was on sale and ended up costing less than the green stuff.
    I had to go to the Cadillac dealer where I live and pick up a pack of 5 GM coolant supplement tablets.
    I added 3 to the radiator. The package says all 5 tablets treat up to 37 quarts, so I did the math as my radiator holds 11.5-12 quarts.
    The lowest the normal operating tempurature was before I drained and refilled was 196. That is still the lowest it goes now as a normal operating temp.
    Before, while i would be sitting in traffic, i've seen the readout say 223 or 225.
    Now while sitting in traffic it reads between 201-214. I'm guessing i dont have any overheating problems or trouble related to my water pump or radiator.
    Thank GOD!
    Later

  13. #12
    Clark in Aloha Land is offline Cadillac Owners Member
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    Re: 4.9 coolant flush and fill procedure!

    The drain is the same on the 1991 Seville but I think Cadillac wanted you to play, "find the valve," or have very small hands. Why they wanted to make something so in demand be so hard to reach is the question. I drained the old coolant, added a jug of flush and drove for the day, (over 50 miles.) Then drain the dirty flushing water/coolant out. I removed the heater hose at the tee close to the firewall, turned the heater temperature controls to as high as they would go, inserted a garden hose into the radiator and turn on the water just enough to get a good stream of water running out of the hose connection and filler. Start the engine and run about 30 minutes or until the water draining and overflowing is clean. Now looking down into the radiator it will be shinny clean. I reconnected the hoses, closed the drain and refilled the system with 50/50 coolant. This is the best way, as you do not need to add water. Everyone should know what is in there water if you mix your own coolant. This is not a good idea and if you must mix use distilled water. Be sure to clean the overflow tank as well and add the correct level to it as well as the radiator. After you heat up and cool down the engine re-check the coolant level the next day. Take good care of your cooling system, as in today’s cars there is not much tolerance.

  14. #13
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    Re: 4.9 coolant flush and fill procedure!

    Quote Originally Posted by Clark in Aloha Land View Post
    The drain is the same on the 1991 Seville but I think Cadillac wanted you to play, "find the valve," or have very small hands. Why they wanted to make something so in demand be so hard to reach is the question. I drained the old coolant, added a jug of flush and drove for the day, (over 50 miles.) Then drain the dirty flushing water/coolant out. I removed the heater hose at the tee close to the firewall, turned the heater temperature controls to as high as they would go, inserted a garden hose into the radiator and turn on the water just enough to get a good stream of water running out of the hose connection and filler. Start the engine and run about 30 minutes or until the water draining and overflowing is clean. Now looking down into the radiator it will be shinny clean. I reconnected the hoses, closed the drain and refilled the system with 50/50 coolant. This is the best way, as you do not need to add water. Everyone should know what is in there water if you mix your own coolant. This is not a good idea and if you must mix use distilled water. Be sure to clean the overflow tank as well and add the correct level to it as well as the radiator. After you heat up and cool down the engine re-check the coolant level the next day. Take good care of your cooling system, as in today’s cars there is not much tolerance.
    Setting temperatur at 90F has nothing to do with flow of the coolant through the heater core... It only opens up the airmix door.

  15. #14
    92EldoTC's Avatar
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    Re: 4.9 coolant flush and fill procedure!

    running a water hose through the cooling system is not a good idea. Its like putting a 50/50 mix of coolant and tap water and then adding cooling tabs, it defeats the purpose.
    On my flush procedure, I used a whole gallon of distilled water and poured it down the filler neck.
    Then i mixed another 1/2 gallon distilled water with the dex-cool.
    I heard tap water is the enemy of an aluminum engine's cooling system!
    HUF, could I have gotten away with filling the system with 50/50 premixed coolant?
    thanks

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    Re: 4.9 coolant flush and fill procedure!

    Quote Originally Posted by 92EldoTC View Post
    running a water hose through the cooling system is not a good idea. Its like putting a 50/50 mix of coolant and tap water and then adding cooling tabs, it defeats the purpose.
    On my flush procedure, I used a whole gallon of distilled water and poured it down the filler neck.
    Then i mixed another 1/2 gallon distilled water with the dex-cool.
    I heard tap water is the enemy of an aluminum engine's cooling system!
    HUF, could I have gotten away with filling the system with 50/50 premixed coolant?
    thanks
    Why to pay extra for premixed coolant when distilled water is widely available? What I usually do is siphoning through the neck about 1.5 gal and refilling with fresh mix and bar's leaks. Sure I add some coolant next morning, after the air gets out and the coolnt is sucked back to the radiator from the surge tank. Taking into account that not all the coolant is changed I repeat the procedure every year. Not a big deal, not messy and makes me feel better. LOL

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