Coolant Flush
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TECH Apprentice
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From: Massachusetts
Coolant Flush I know this dexcool vs green stuff topic has been beaten to death. I'm thinking about moving to the green stuff. Of course, I need to make sure my system is flushed. My question is......is it absolutely necessary to remove the engine block plugs? I'm hesitant to do it, because I really don't want to strip the aluminum. If I just run water through the system and then drain it two or three times, will it be enough to remove the old dexcool?
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My mechanic did my coolant flush (Dexcool to green Prestone 50-50) in April 2014 which is just about 6 years and 30,000 miles ago. He wrote in the comments section that he flushed the entire system twice. He did not remove the plugs. I've been on two long New England trips since then plus a Florida trip. No cooling issues at any time. Obviously he did a fine job and you should be fine too.
Yes, it is necessary to remove them if you want a proper flush and I would definitely do this if you are going to change the coolant type. Running water through the system will just dilute what's left more and more. The offending chemicals that would contaminate the new coolant would never fully get out of the system but...
If your motivation to do this swap is to protect your heater core, the red coolant should give you better protection. If you have concerns about the red, you can just flush it at the same interval as the green and you are no worse off, except you will have extra cushion in there.
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From: Schiller Park, ILL Member: #317
I would just stick with Dexcool, it doesn't cause any issues in a properly maintained LS1 cooling system. 22 years of Dexcool in my '98 with zero troubles. To be honest, I only did a complete flush one time in the entire life of this car, that was to get the original assembly line coolant out when it hit the ~5 year point (which is the recommended change interval). Since then, I've only ever done partial changes (drain and refill) every 2 years, which has worked out great with no problems. If you are starting with a system of unknown or questionable previous service intervals, I would definitely recommend a complete flush (perhaps twice at this age - and don't forget to clean the expansion tank as well) to get things cleaned up. Going forward, you could then do more frequent drain/refill intervals to avoid the hassle of such a comprehensive flush, or just do a complete flush every 5 years (as recommended by the factory).
FWIW, the old "green stuff" is no magic shield against cooling system issues/deterioration. I've owned my share of cars from the '70s, '80s and early '90s, all built prior to the introduction of Dexcool or other generic extended life coolants; leaking heater cores, leaking radiators, failed water pumps and leaking gaskets happened to those cars just the same (actually, even more often in my experience). The key is to maintain the system properly, no matter which coolant type you use.
FWIW, the old "green stuff" is no magic shield against cooling system issues/deterioration. I've owned my share of cars from the '70s, '80s and early '90s, all built prior to the introduction of Dexcool or other generic extended life coolants; leaking heater cores, leaking radiators, failed water pumps and leaking gaskets happened to those cars just the same (actually, even more often in my experience). The key is to maintain the system properly, no matter which coolant type you use.
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FWIW the dealership flushed/converted to green on my 96 back in 98 under warranty. It was the brown sludge problem so much they also had to replace the reservoir also. Been green ever since
You do not want to cross mix Dex & Green so do a complete flush. Use distilled water if mixing any coolant 50/50
Toyota insists or red, Subaru on the blue. GM, Ford typically Dex
My neighbor is a mechanic for Caltrans (CA road guys) They converted all their fleet vehicles from Dex to green to stop the chronic plastic part failures in the cooling systems from the Dexcool. I believe this was the interaction of Dexcool with factory installed stop leak pellets in so many vehicles back in the late 90's. I believe manufacturers have stopped using those pellets with Dexcool now.
Dexcool was intended to last 100k mi so it mirrored the "no major service until 100k mi" of new cars back when it was introduced in 96
You do not want to cross mix Dex & Green so do a complete flush. Use distilled water if mixing any coolant 50/50
Toyota insists or red, Subaru on the blue. GM, Ford typically Dex
My neighbor is a mechanic for Caltrans (CA road guys) They converted all their fleet vehicles from Dex to green to stop the chronic plastic part failures in the cooling systems from the Dexcool. I believe this was the interaction of Dexcool with factory installed stop leak pellets in so many vehicles back in the late 90's. I believe manufacturers have stopped using those pellets with Dexcool now.
Dexcool was intended to last 100k mi so it mirrored the "no major service until 100k mi" of new cars back when it was introduced in 96
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From: Schiller Park, ILL Member: #317
Interesting information about the stop-leak pellets, I don't think I've heard that before.
In the early years of Dexcool, I do remember there being some adverse events relating to gasket compatibility with certain older applications; I seem to recall one or two specific engine platforms really seeing the brunt of this in a catastrophic way. My '96 Bonneville (L36 3.8L) had the very common intake gasket leak early in its life, though I wouldn't necessarily place the blame for this on Dexcool alone (nor would I include the L36 in the group with severe compatibility issues related to Dexcool).
Regardless, none of this was ever an issue with LS1s; they have no problems with Dexcool as long as the system is properly maintained. The factory recommended service interval is 5 years or 150k miles, but I've always changed it well before that mileage as I've never driven any vehicle often enough to hit 150k miles prior to the 5 year mark.
In the early years of Dexcool, I do remember there being some adverse events relating to gasket compatibility with certain older applications; I seem to recall one or two specific engine platforms really seeing the brunt of this in a catastrophic way. My '96 Bonneville (L36 3.8L) had the very common intake gasket leak early in its life, though I wouldn't necessarily place the blame for this on Dexcool alone (nor would I include the L36 in the group with severe compatibility issues related to Dexcool).
Regardless, none of this was ever an issue with LS1s; they have no problems with Dexcool as long as the system is properly maintained. The factory recommended service interval is 5 years or 150k miles, but I've always changed it well before that mileage as I've never driven any vehicle often enough to hit 150k miles prior to the 5 year mark.
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From: Massachusetts
Thanks for all the help everyone. I'm going to stick to dexcool. I haven't had any problems with a 20 year old car on it so I should be fine. And since I don't have to worry as much about completely getting rid of it, I won't bother removing the plugs. I will just flush the system twice.
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From: Massachusetts
Nothing to worry about. The two plugs you would need to remove are threaded and sealed with a soft sealant. (They are special drain plugs for this purpose, not like the other permanently sealed freeze plugs on the engine.) Like all fasteners - start the plugs back in by hand and then tighten with a wrench and you'll be just fine.
Yes, it is necessary to remove them if you want a proper flush and I would definitely do this if you are going to change the coolant type. Running water through the system will just dilute what's left more and more. The offending chemicals that would contaminate the new coolant would never fully get out of the system but...
If your motivation to do this swap is to protect your heater core, the red coolant should give you better protection. If you have concerns about the red, you can just flush it at the same interval as the green and you are no worse off, except you will have extra cushion in there.
Yes, it is necessary to remove them if you want a proper flush and I would definitely do this if you are going to change the coolant type. Running water through the system will just dilute what's left more and more. The offending chemicals that would contaminate the new coolant would never fully get out of the system but...
If your motivation to do this swap is to protect your heater core, the red coolant should give you better protection. If you have concerns about the red, you can just flush it at the same interval as the green and you are no worse off, except you will have extra cushion in there.
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From: Woodstock, GA
For what it's worth, I flushed out the dex for the green a few hundred thousand miles ago and haven't had any issues with the freeze plugs or anything else for that matter. I'm at 363,000 miles now.
