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I'm looking to buy a low mileage ( 100k km / 62k miles ) 03 Buick LeSabre for my wife. The 3800 V6 runs Dexcool, and I've heard horror stories about Dexcool, but I've also read other opinions that it's not a problem at all as long as

  1. air doesn't get into the cooling system.
  2. The engine doesn't pass coolant through the intake manifold

So... The 3800 V6 in the LeSabre passes coolant through the intake manifold and seems to be known for having issues with the intake manifold gasket failing around 60k miles, and there was apparently a class action lawsuit claiming that it's due to the Dexcool.

If the vehicle is running Dexcool, should I flush it and install a different coolant, and if so what?

As a bonus, is there anything specific I should look out for with this vehicle beyond the typical inspection routine?

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Dexcool has a tendency to cause corrosion and sludge if air is introduced into the cooling system primarily through leaks. It also has had a deteriated effect on gaskets made of a certain materials. The newer models and car parts have adapted to the deteriation part of the problem by using gaskets made with compatible materials. One should never swap coolant types while under warranty. But after that you will find extremely knowledgeable and experianced mechanics recommending getting rid of Dexcool and replacing it, and there are just as many recommending to leave the Dexcool in.

I can't reference a source. But when I was in college I've watched demonstrations of disassembled engines that had sludge built up in the coolant passages with dexcool at around 100,000 miles. I can't quote the sources, but upon doing investigations on the internet I've seen good articles on the effects of air introduced with dexcool. I worked for a shop owner that was the most knowledgeable person I know in the automotive field in my area. He would replace all his customers dexcool vehicles with green when he did cooling system work, as long as they were not under warranty for these reasons. I have never witnessed this sludging but I am satisfied with the research I've found to change out dexcool the first time I do a coolant drain or change.

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  • Do you have any references for any of this? I've personally used Dexcool in my GM vehicles without issues since GM started using it ... There have been plenty of rumors about it, but I've never actually seen anything from any knowledgeable source which gives me a good reason not to use it. – Pᴀᴜʟsᴛᴇʀ2 Apr 26 '20 at 11:56
  • I've added to my answer the reasons I believe my anti Dexcool rant. – Jupiter Apr 27 '20 at 22:44
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If I were you, I'd get rid of that Death-Cool ASAP and replace it with something like Prestone Yellow, Peak Global, Turbo Power (RecoChem) Global or Prestone Celsius. They can be used in all makes, all models and mix safely with all other antifreeze colours. They are five-year longlife antifreezes so there's no loss of longevity and they don't do the damage that Death-Cool does:

GM Owners Still Steaming Over Dex-Cool "Aug 29, 2006 - Ten years after General Motors began using Dex-Cool as an antifreeze in most of its cars and light trucks, GM car and truck owners continue to complain that the coolant corrodes and clogs radiators and radiator caps, erodes water pumps, rots radiator hoses, causes chronic overheating and engine damage while leading to ..." https://www.consumeraffairs.com/news04/2006/08/gm_dexcool.html

The Global formulations are also less expensive than Death-Cool and in a pinch, you can top them up with anything without worry of problems because they won't react adversely to being mixed with another colour.

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