How to properly switch from red to green in a 2000 STS
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Northstar Engines and System Technical Discussion Discussion, How to properly switch from red to green in a 2000 STS in Cadillac Engine Technical Discussion; Please, Please, PLEASE do not respond if you want to debate on why I should keep the red in or ...
  1. #1
    osu411yamaha is offline Banned
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    How to properly switch from red to green in a 2000 STS

    Please, Please, PLEASE do not respond if you want to debate on why I should keep the red in or debate about which type of coolant is better. I dont care


    I simply want to know the BEST way to change my coolant tomorrow so that I can get all or close to all of the red out before I put the green back in. My initial gameplan is to simply drain it all from the drain valve on the radiator, fill with pure distilled water in the surge tank, run the engine for a few minutes, drain, and repeat multiple time until the coolant gets diluted enough. I figure this method would allow me to get most of the coolant that lies on the bottom of the radiator below the drain plug.

    If anyone knows a better method please let me know....

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    CadillacSTS42005's Avatar
    CadillacSTS42005 is offline Banned
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    Re: How to properly switch from red to green in a 2000 STS

    you will never remove all the chemical attirbute which have been instilled into that coolant system so forget that idea right now

    your way with a hose into your upper hose to flush the system is as good as your going to get but its a significant waste of your time money and water

    to each their own

  4. #3
    jeffrsmith is offline Cadillac Owners Fanatic
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    Re: How to properly switch from red to green in a 2000 STS

    STS2003 pretty much hit the nail square on the head.

  5. #4
    osu411yamaha is offline Banned
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    How to change from Dex-Cool to Green Coolant in a Northstar

    Here is how I changed from Dex-Cool to green ethylene-glycol coolant in my Northstar. To give a little run down I was up for a coolant change. I could have put the red back in, but with all of its negative publicity why bother? I have NEVER heard anything bad about the green now that they have started removing the silicates from it. Even if there is only a slight chance of the dex-cool being the infamous n* headgasket culprit I figure why risk it.....

    With that said here is what I did and my methodology behind it. My car is a 2000 STS so you may have to modify this method slightly, but it should work with most, if not all northstar engines.

    OSU411Yamaha's Repeated Dilution Method

    Step 1-Find a bucket with at least a 2 gallon capacity that will fit below your cars radiator without jacking it up. I think not jacking it up is the best method as you will be able to get more of the old coolant out.

    Step 2-Warm your engine, but dont allow it to get too hot.

    Step 3-First remove the cap from your surge tank as this will remove the pressure from the cooling system and allow it to flow out of the drain more quickly.

    Step 4-With a 19mm deep socket remove the drain plug from the driver's side bottom of your radiator and quickly slide the bucket under to catch the coolant.

    Step 5-Once all dripping has stopped put the drain plug back on and tighten.

    Step 6-Add 1.5 gallons of distilled water to the surge tank and put the cap back on. It is arguable if tap water is just as good, but I figure as cheap as distilled water is why risk it? I also don't believe any flushing chemicals should be used as they have been known to be too harsh on the engine.

    Step 7-Start the car and turn the heaters on full blast.

    Step 8-Allow the car to run 5-10 minutes and occasionally rev the engine.

    Step 9-Turn the car off and allow to cool slightly,

    Step 10-Repeat steps 3 through 9 until the coolant is diluted to your liking. The beauty in this method is that if you use the new Prestone Green coolant that can be mixed with anything you dont have to get every last drop of the Dex-Cool out. Which is impossible in my opinion anyway unless you use a vacuum flush which opens up a possible whole new set of problems. I also don't recommend the Peak green coolant as it contains silicates which are known to destroy water pumps.

    Step 11(optional, but highly recommended)-Drink a cold one(preferably Sam Adams Boston Lager)






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    ThumperPup's Avatar
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    Re: How to properly switch from red to green in a 2000 STS

    From what i have heard is

    even if you do the regulare flush and then also do a back flush to run all the crack in there up and threw the top you can do a forward flush and a back flush and it still wont get all the crack out of there so
    not tryign to debate just saying it's not worth it even if you flush it both way slike 3 or 4 times you wont get it all out

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    Re: How to change from Dex-Cool to Green Coolant in a Northstar

    I would think that even if not changing from red to green a through and complete flush would be mandatory.
    I'm having the cooling system fluid changed in my 98 D'ville reds going back in the system but a complete flush is part of the procedure.
    The mechanic doing my car says he sucks the fluid out of the reservoir tank and will cycle the system with fresh water using a coolant flush system his shop has.
    when learning about the different anti-freeze and their properties:
    I found this article an interesting read and explains some whys and why not's.
    thanks for the post and looking froward to hear how the change may help the cooling in your car.
    I'm sticking with what OEM recommends.

  8. #7
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: How to properly switch from red to green in a 2000 STS

    Rodney, Don't forget that just over 2 quarts of liquid remains in the engine block (there are no block drains) when you drain the system from the radiator plug. If you do multiple fresh water flushes, then drain/fill the system, take into account that you need to mix your new coolant a tad "heavier" than 50/50 in order to bring the total fluid concentration close to 50/50 or better.

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    Rodney_98's Avatar
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    Re: How to properly switch from red to green in a 2000 STS

    Quote Originally Posted by submariner409 View Post
    Rodney, Don't forget that just over 2 quarts of liquid remains in the engine block (there are no block drains) when you drain the system from the radiator plug. If you do multiple fresh water flushes, then drain/fill the system, take into account that you need to mix your new coolant a tad "heavier" than 50/50 in order to bring the total fluid concentration close to 50/50 or better.
    I'll pass that along to the mechanic. Thanks

  10. #9
    97EldoCoupe is offline Owner of Northstar Performance
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    Re: How to properly switch from red to green in a 2000 STS

    Now to what OSU411YAMAHA said, turning the heater on will not turn on the flow to the heater core. There are no valves in line like the old cars used to have, there is coolant circulating through the heater core at all times. With the older cars that was necessary.

    Repeatedly diluting the system is all that can be done, short of removing the block and flipping it over.

  11. #10
    Heart-of-Ohio is offline Cadillac Owners Member
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    Re: How to properly switch from red to green in a 2000 STS

    Being that we're discussing red to green coolant; when I replaced my radiator a month ago, the coolant that I drained out of the old was a mix of red and green. This drained red/green coolant mix, from the previous owner, was very strange looking. The red and green anti-freeze was separted. In the drainage container the red coolant was on the bottom with the green coolant separated floating on top.

    I certainly hope that this old coolant mix does not cause any future problems.

    After draining the old system, I flushed with distilled water until the coolant that I was catching looked clean before adding new anti-freeze/coolant.

  12. #11
    osu411yamaha is offline Banned
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    Re: How to properly switch from red to green in a 2000 STS

    Yes thats one reason why I was saying dont use the Peak green. The new Prestone green is mixable with the red, but the Peak doesnt seem to be. My grandpa used to just pour either one randomly in his radiator when he had a coolant leak on his eldorado. It seperated and sludged up bad......I recommend doing my method, but with even more dilutions to get as much of that out as possible and then replacing with the Prestone green....

  13. #12
    Necrosan is offline Cadillac Owners Enthusiast
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    Re: How to properly switch from red to green in a 2000 STS

    I've always had great success with the Prestone "Flush-N-Fill" kits.
    Certainly a lot easier than constantly draining/refilling.

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