4.9 coolant flush and fill procedure! - Page 2
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HT4100 4.1, 4.5, 4.9 Discussion, 4.9 coolant flush and fill procedure! in Cadillac Engine Technical Discussion; Originally Posted by HUF Setting temperatur at 90F has nothing to do with flow of the coolant through the heater ...
  1. #16
    100
    100 is offline Cadillac Owners Enthusiast
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    Re: 4.9 coolant flush and fill procedure!

    Quote Originally Posted by HUF View Post
    Setting temperatur at 90F has nothing to do with flow of the coolant through the heater core... It only opens up the airmix door.
    I have been wondering about this. Almost everybody says to set the heater max., but the way the heater system is set up, it seems to me that there is always constant flow of coolant going in. I agree with HUF. That must be correct, I think.

  2. #17
    HUF's Avatar
    HUF
    HUF is offline Cadillac Owners Connoisseur
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    Re: 4.9 coolant flush and fill procedure!

    Quote Originally Posted by 100 View Post
    I have been wondering about this. Almost everybody says to set the heater max., but the way the heater system is set up, it seems to me that there is always constant flow of coolant going in. I agree with HUF. That must be correct, I think.
    100,

    The reason people follow the advice to turn the heat up is that in older cars the flow through the heater core actually was variable. That is not a case in our cars. No matter what is the setting the same volume of hot coolant flows through the heater core. The bad thing is that all the computers (ECM, BCM, programmer) are in close proximity of the heater core. It might be one of the reasons they move to south in some 10-15 years of service.

  3. #18
    92EldoTC's Avatar
    92EldoTC is offline Cadillac Owners Enthusiast
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    Re: 4.9 coolant flush and fill procedure!

    i hate the idea of having old coolant still left in the system. The coolant i had left in mine was green so I noticed it easy. It wasnt a funny color green though, just a normal healthy looking green.
    I guess its not so bad if its left in there and is a normal color.
    later

  4. #19
    100
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    Re: 4.9 coolant flush and fill procedure!

    I kind of understand how you feel about leaving old stuff in. But it does not hurt. And I think color really does not tell you anything any more. With an iron engine, you could tell (if you waited too long)... So, even if it looks nice green, it does not mean health, unless you know chemistry in it, I suppose... In fact, I have heard that one of the reasons GM stopped putting those tabs was that customers complained about coolant color. They do make coolant look dirty...

    Let's just keep up coolant change!

    Quote Originally Posted by 92EldoTC View Post
    i hate the idea of having old coolant still left in the system. The coolant i had left in mine was green so I noticed it easy. It wasnt a funny color green though, just a normal healthy looking green.
    I guess its not so bad if its left in there and is a normal color.
    later

  5. #20
    BRyan77 is offline Cadillac Owners Member
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    Re: 4.9 coolant flush and fill procedure!

    I found the drain plug pretty easily. I got it to turn, and it has screwed out a bit, but it seems to just turn and turn, but no coolant comes out. The radiator is full. How far out does it have to go for the coolant to come out the bottom??

  6. #21
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    Re: 4.9 coolant flush and fill procedure!

    Quote Originally Posted by BRyan77 View Post
    I found the drain plug pretty easily. I got it to turn, and it has screwed out a bit, but it seems to just turn and turn, but no coolant comes out. The radiator is full. How far out does it have to go for the coolant to come out the bottom??
    If I remember right, you can or have to pull the plug out entirely. There also may be some debris that has settled into and plugged the drain hole. You may have to stick a paper clip end or something like that in there to loosen the debris.

  7. #22
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    Re: 4.9 coolant flush and fill procedure!

    I wouldnt put dexcool in a 4.9. Or anything for that matter. It has corrosive properties and the metals and gasket materials in your 4.9 werent made to jive with it.

  8. #23
    drewsdeville's Avatar
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    Re: 4.9 coolant flush and fill procedure!

    Quote Originally Posted by Sevillian273 View Post
    I wouldnt put dexcool in a 4.9. Or anything for that matter. It has corrosive properties and the metals and gasket materials in your 4.9 werent made to jive with it.
    Internet myth :/

    What particular 4.X specific metals and gasket materials are incompatible?

    I've been using Dexcool in all of my GM cars since I could drive. My current '95 and '90 both have it. I had a vacuum leak at the intake gasket on my '90, not related to coolant, but no other gasket issues.

    I suggest you use what you like, it all does the same thing...transfers heat, lowers freezing point, raises boiling point and is corrosion RESISTANT. The important thing is to make sure you keep a consistent maintenance schedule.

  9. #24
    HUF's Avatar
    HUF
    HUF is offline Cadillac Owners Connoisseur
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    Re: 4.9 coolant flush and fill procedure!

    That' s how I replaced the coolant on my 91 Seville. YOu will get 1 or 1.5 gallon of coolant. Pretty good if you repeat the procedure every other year. Very easy and no mess.

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