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Hello I realized today after beating my head about my car's overheating problems that I have the wrong coolant in it.

About a year ago, my car ran dry. At the bottom of the expansion tank was an orange crust(also the manual recommend DexCool.. ). I ignored the Dexcool warning in my manual as one of those "you also need to take it to a certified dealer to get the oil changed" type of warnings. So I filled it up with green coolant. Well, reading up more I realize that I'm wrong.

About 6 months ago, I had a wreck and got the radiator replaced(salvaged) and the mechanic(who I'm convinced now is an idiot) filled it up with green coolant along with leaving several leaks. I took it to another mechanic and after fixing the leaks, he also filled it up with green coolant.

So I've been running green coolant for about a year now. How exactly should I go about switching to the proper Dexcool coolant? Would it do more harm than good to switch now?

Also, my car is having problems in that it overheats when sitting in traffic or idling. It doesn't have problems when going 65MPH or so. Could this cause this kind of problem?

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As long as you don't mix the two coolants together you should not have any problem. I run "green" coolant in my GM that came with Dexcool, and have been for more than 5 years. You do want to check the ratio of coolant and water as straight coolant (or too much compared to water) will not cool as well.

To answer your question I wouldn't bother switching, if you decide to do so anyway simply flush the system and refill with the coolant of your choice.

To address your overheating concern, if it only overheats sitting still you need to check the fan operation and the shroud around the fan and radiator. Another possibility is the water pump, I have seen the fins wear off and the water pump stop circulating coolant, if yours is starting to do this it may not be circulating enough water at the lower RPM's at idle.

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  • Wait so you can have too much coolant? (too concentrated)?
    – Earlz
    Jul 29, 2011 at 18:41
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    Yes, 50/50 is what you should shoot for 70/30 is max 70 coolant/30 water
    – Move More Comments Link To Top
    Jul 29, 2011 at 19:00
  • this may be my problem them. I'm pretty sure it's 90 or 80 percent coolant right now. I'm going to try siphoning out some coolant from the expansion tank and replacing it with distilled water. If this fixes it, then I'll be pretty angry that it's such a simple solution :)
    – Earlz
    Jul 29, 2011 at 20:04
  • Ok I took all the antifreeze out of my expansion tank and filled it with water. Over a day or two if it doesn't improve, I'll assume it's either coolant type, water pump, or at worst case partially blocked radiator
    – Earlz
    Jul 29, 2011 at 21:44
  • I'm not a particular fan of Dexcool anyway, so I wouldn't necessarily recommend going back to it. If you have the sludge that you get in the cooling system if it's been mixed with regular coolant, the whole system has to be flushed to clear out traces of the old coolant and the sludge before you can put either coolant in. That might solve your overheating problems if it's done properly, but it's quite labor intensive and thus not cheap. OTOH you'll never get rid of the sludge by other means.
    – Timo Geusch
    Aug 1, 2011 at 21:47
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The overheating is likely caused by a non-working fan. When you are speeding, the air you run into cools it, but in traffic the radiator experiences no flow. As far as the coolant, you can have it flushed with the DexCool again, but personally I run BMWs blue coolant in my S10... So the coolants all work the same, and Chevrolet just prefers the red. Theoretically, you likely have no DexCool left after so many people have messed with your system, so it should be OK.

Edit: Also, as pointed out, ensure your radiator does not have any crushed tubes, or bent fins, as this might make it extremely inefficient. If it was not the right part number, than it might not cool enough fluid to meet the needs of your vehicle.

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  • If you do decide to get DexCool flushed back in, ensure they drain your engine as well.
    – FossilizedCarlos
    Jul 29, 2011 at 18:35
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    you might want to point out that the salvaged radiator (the replacement) could also be inefficient or simply too small.
    – Bob Cross ♦
    Jul 29, 2011 at 19:01
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    @Bob I missed that, need to read slower O.o Thanks for pointing it out.
    – FossilizedCarlos
    Jul 29, 2011 at 19:05
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If the green coolant is dexcool compatible, then there's no pressing need to switch. Most (but not all) off the shelf pre-mixed coolants are compatible with just about everything and can even be used for topping off systems full of other coolants. However, topping off a red/orange system with green will tend to make for funny brown looking coolant that could potentially mask other problems (hard to check for coolant contamination if it's all nasty looking already).

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