Is DEX save for engines?
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Northstar Engines and System Technical Discussion Discussion, Is DEX save for engines? in Cadillac Engine Technical Discussion; Have been noticing a bit of what I think might be overheating of my 98 Deville Northstar on pulling hills ...
  1. #1
    res1n9k9 is offline Cadillac Owners Member
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    Is DEX save for engines?

    Have been noticing a bit of what I think might be overheating of my 98 Deville Northstar on pulling hills or driving slow...coolant temps have gotten up to 229, not sure if that is "normal" for the northstar or not?? (However, the overtemp idoit light has never came on yet.) Only have 31K miles on it, yep and is a 98...typical story...little ol' lady kept in garage and didn't drive if much. Ok, so not sure if I have a problem of not...thinking about flushing system and putting in new pre-mix DEX..but hearing scary stuff about DEX....what is the "truth" on DEX?? (And how will I recognize the truth??) Also considering changing out thermostat?? But car runs at 196-201 on mostly level roads. Also noted it seems to burn off about quart of oil (I'm using synthetic oil - Mobil 1) after about 1000 or so miles??

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    ewill3rd is offline Cadillac Technician
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    Re: Is DEX save for engines?

    If you play with the search engine on this website you'll find tons of information on Dex cool. There is nothing wrong with it, despite the massive amount of rumor and speculation.
    The biggest problem with Dex cool is that people ignore their cars by not maintaining them and then when something goes wrong they blame it on the car instead of owning up to being lazy.
    At any rate, just do some searching and you'll get plenty of stuff to read.

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    AJxtcman's Avatar
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    Re: Is DEX save for engines?

    From everything I have ever read about Dex-Cool. Dex-Cool is the best Coolant on the market. The reason for Dex-Cool is to save the environment. They removed a component that was sand like. This component killed water pumps and caused the need to have the coolant changed every year. All that coolant going in the lake and rivers is no good. They are both Diethylene glycol or Ethylene glycol. I worked at a chevy dealer and saw some problems with blazers, but after looking at all the data. I know it was not a Dex-Cool problem. They just removed the Silicate in the coolant.
    .
    I have been in plenty of arguments over the myths of Dex-cool with other Techs. ewill3rd is correct do some research and you will find that it is safer than the older coolant.

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    Re: Is DEX save for engines?

    Dexcool, especially in Northstars, has an excellent record. There's one example where Dexcool being installed in certain 4.3L V6 engines "caused" sludge and scale in the system. It's known that the cause wasn't the coolant, but the lack of maintenance, but the rumors persist. In fact, Dexcool is MORE RESISTANT to sludge formation vs. the old green coolant.

    Doing a drain and refill with Dexcool is the best thing you can do. Buy a package of cooling system sealing pellets at your GM dealer (they'll know what you're asking for) and drop those into the lower radiator hose when you have it off.

    By the way, 229*F is perfectly normal for the Northstar, under the conditions of which you speak. That's when the cooling fans FIRST ENGAGE, on LOW speed. At about 234*F, they'll switch to HIGH speed. If the engine gets up over 240*F and stays there, then you may have an issue, but anywhere under the point where the cooling fans come on HIGH speed is perfectly fine. You may think that the fans aren't even on -- they're pretty quiet on the low speed.

    Regarding your oil economy, 1 qt in 1000 miles is on the cusp of being too much, but some engines will see that. Ditch the synthetic oil and try some conventional. You may see the consumption reduced. Many folks report excessive consumption when using synthetic oil.

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    Re: Is DEX save for engines?

    All good replies...

    If I may add, the interval for dexcool is 100,000 or 5 years. Thus, in 2003, you should have changed the coolant, and in 2008, change it again, despite your miles being so low.

    So, if you've never done it, do it. Like, yesterday...

    You can do it yourself for around $22... for that price, I do mine every fall...

    As far as your oil burning, check the technical archive section at the top of the forums... lots of good information on WOTs, and why they're good for your engine....

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    Re: Is DEX save for engines?

    Keep in mind, never mix a Dex with a tap water only use a distilled water just like you should do in green coolants

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    Re: Is DEX save for engines?

    By the way, 229*F is perfectly normal for the Northstar, under the conditions of which you speak. That's when the cooling fans FIRST ENGAGE, on LOW speed. At about 234*F, they'll switch to HIGH speed.
    I think they come on low at 224 and high at 229 give or take a degree.

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    Re: Is DEX save for engines?


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    Re: Is DEX save for engines?

    Quote Originally Posted by Ranger View Post
    I think they come on low at 224 and high at 229 give or take a degree.
    No, it's 229/234, on the older (90s) ones. I believe it's probably the same through current.

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    Re: Is DEX save for engines?

    If the engine doesn't have DEX in it now then you're wasting your time filling with DEX. You'll never get all the other out AND the engine has already been subject to it. Drain and refill with fresh Prestone. Do that every 3 years and you'll be fine.

    DEX is a great coolant but once you put the regular green coolant in an engine it's pointless to switch to DEX.
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    Re: Is DEX save for engines?

    Quote Originally Posted by jadcock View Post
    No, it's 229/234, on the older (90s) ones. I believe it's probably the same through current.
    OK, you got me wondering so I checked the FSM. Per the '03 manual, low comes on at 223 and high at 234. Maybe other years vary. I have an '02 manual but did not think to compare.

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