How to properly do a Coolant Flush?
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Cadillac STS Forum - 2005 through 2012 Discussion, How to properly do a Coolant Flush? in Past Cadillac Vehicle Discussion; I drive a 2005 STS V8 1SE. Per the owner's manual the coolant needs to be changed every 100K/5 years. ...
  1. #1
    ChrisShaw is offline Cadillac Owners Member
    Automobile(s): 2005 STS V8
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    How to properly do a Coolant Flush?

    I drive a 2005 STS V8 1SE. Per the owner's manual the coolant needs to be changed every 100K/5 years. Well, I am only at 32k but at the 5 year mark.

    I searched the forums and didn't come across anything yet.

    Is this something you guys recommend doing? Anybody know how to do it? Any pics/diagrams?

    Thanks,
    Chris

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  3. #2
    1BadCadSTS's Avatar
    1BadCadSTS is offline Cadillac Owners Connoisseur
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    Re: How to properly do a Coolant Flush?

    Drain and fill would be easiest. There should be a petcock on the side rad tank, use that to drain the rad then fill with 50% straight Dex and 50% distilled water. You'll be there for days trying to get it all out but a simple drain/fill is fine.

  4. #3
    ChrisShaw is offline Cadillac Owners Member
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    Re: How to properly do a Coolant Flush?

    Is the 50/50 mix STRICT for the STS? I have read others will flush distilled water through the system to get rid excess sediment. Sounds like a good idea, but the downside is not all the water will escape. Thus, you technically throw off the 50/50 mix when you go to refill.

    Any thoughts?

  5. #4
    EChas3's Avatar
    EChas3 is offline Cadillac Owners Master
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    Re: How to properly do a Coolant Flush?

    You'd have to measure what you drain to ensure a 50/50 mix. 60% Dexcool provides the coldest protection. More than that actually reduces protection (if I remember right.)

    I specified 50/50 when my dealer replaced the waterpump at about 55,000.

  6. #5
    C&C's Avatar
    C&C
    C&C is offline Cadillac Owners Connoisseur
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    Re: How to properly do a Coolant Flush?

    I was toying with the idea of changing the coolant mysef but my dealer gave me a price of, I believe around $135, and since it included drain, flush and refill, I went that route. Just a drain and fill is going to leave a substantial amount of old coolant in the system.

  7. #6
    ChrisShaw is offline Cadillac Owners Member
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    Re: How to properly do a Coolant Flush?

    Manual says 13.0 quart coolant capacity. Can anybody verify this?

    Is air in the system going to be a problem for a drain and fill? Does our car have a way to prevent/remedy this?

  8. #7
    EChas3's Avatar
    EChas3 is offline Cadillac Owners Master
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    Re: How to properly do a Coolant Flush?

    The manual is right. I haven't had any trouble with air in the system after the dealer replaced the water pump and did the flush & fill.

  9. #8
    ChrisShaw is offline Cadillac Owners Member
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    Re: How to properly do a Coolant Flush?

    I tackled it this afternoon, and it went very well. The dealer's option of $140 doesn't sound that bad in retrospect. But for those who want to save a few $$, here is how I did it.

    The STS V8 has a 13.0 quart coolant capacity. The petcock from the radiator drains approx 6 - 6.5 quarts. This leaves 6.5 quarts of old coolant in the engine block. So, a simple drain and fill won't work. What you have to do is somehow get 13 quarts of pure water into the system so when you drain the petcock you are left with 6.5 quarts of water. You top off with 6.5 quarts of pure DEX and you have your 50/50 13 quart mix.

    To get pure water in the system, I did the following:
    1.) Drain using the petcock (approx 5.5 quarts + 1 quart that spills on the driveway no matter what you do)
    2.) Fill coolant reservoir to the full line with distilled water (approx 6 quarts)
    3.) Turn engine on with heater set to 88 deg, let idle for approx 5 minutes
    4.) Drain using the petcock

    Repeat steps 1-4 until what you are draining is clear. You can do this as many times as you want, but it took me about 5 times.

    I attached some pictures for reference. A few things to keep in mind:
    - The petcock drains everywhere, so have about 4 or 5 catch cans ready at different spots to get accurate drain measurements.
    - On the last fill, it took about 5.5 quarts of DEX to the fill line. I drove around for a few minutes, got the 'Check Coolant Level' on the DIC, returned home and topped off with 1 quart of DEX for my desired 6.5 quarts.

    It took me a few hours to do. Total price was around $30 (2 gallons of DEX plus about 10 gallons of distilled water). I liked doing it myself not only for the savings, but also to guarantee it was a complete flush of the old stuff.

    There could be other ways, but this way worked for me. I hope it helps you, too.
    Attached Images

  10. #9
    turnerbend is offline Cadillac Owners Fanatic
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    Re: How to properly do a Coolant Flush?

    How did the liquid look that you drain from the engine? Were there a lot of sediment or rust in the liquid in you catch can, looks clean to me. What do you accomplish by changing the coolant on a close system????

  11. #10
    Greg00coupe is offline Cadillac Owners Enthusiast
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    Re: How to properly do a Coolant Flush?

    On my 2000 STS there where some tables that you had to put in the lower radiator hose. I think to help keep the head gaskets pliable. Is this not required on our generation of STS Ns????

  12. #11
    ChrisShaw is offline Cadillac Owners Member
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    Re: How to properly do a Coolant Flush?

    turnerbend - The old coolant was pretty much free of sediment. I noticed some, but very very little. I changed the coolant per the owner's manual recommendation since I am at the 5 year mark with my 2005.

    The cooling system in your vehicle is filled with
    DEX-COOL® engine coolant. This coolant is designed
    to remain in your vehicle for 5 years or 150,000 miles
    (240 000 km), whichever occurs first, if you add
    only DEX-COOL® extended life coolant.


    Greg00coupe - I didn't add any tablets. Manual says not necessary.

    Use a mixture of one-half clean, drinkable water and
    one-half DEX-COOL® coolant which will not damage
    aluminum parts. If you use this coolant mixture, you do
    not need to add anything else.

    Notice: If you use the proper coolant, you do not
    have to add extra inhibitors or additives which claim
    to improve the system. These can be harmful.


    The manual also says to use clean, drinkable water. I used distilled. Hopefully it doesn't make a big difference.

  13. #12
    D&Ds_STS is offline Cadillac Owners Member
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    Re: How to properly do a Coolant Flush?

    Quote Originally Posted by ChrisShaw View Post
    The manual also says to use clean, drinkable water. I used distilled. Hopefully it doesn't make a big difference.
    "Clean, drinkable water" can have minerals, chlorine, etc. I would not use tap water in my car's coolant system. I don't drink it either. You done good!

  14. #13
    EChas3's Avatar
    EChas3 is offline Cadillac Owners Master
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    Re: How to properly do a Coolant Flush?

    Quote Originally Posted by Greg00coupe View Post
    On my 2000 STS there where some tables that you had to put in the lower radiator hose. I think to help keep the head gaskets pliable. Is this not required on our generation of STS Ns????
    Those tablets are Stop Leak! The N* was perfected when it was redesigned for RWD. Before that, not so much (IMHO).

  15. #14
    Jpearl01 is offline Cadillac Owners Member
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    Re: How to properly do a Coolant Flush?

    Just bought a 99 SLS and was looking at the coolant and it appears a little nasty. I am considering taking it somewhere just because it cold outside and I have a very small garage to work in. In other forums I have heard many recommendations to get rid of dex-cool coolant and just go with the standard green stuff. The was not for any specific car but just GM in General. Does anyone have any though, comments, experiences, or recommendations on this? I'm surprised that I have not come across anything about this yet.

    Any help is appreciated.

  16. #15
    EChas3's Avatar
    EChas3 is offline Cadillac Owners Master
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    Re: How to properly do a Coolant Flush?

    I'm sticking with Dexcool. You might consider checking out the Northstar or Seville forums to get a feel for what other owners of your year/model car think about it.

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