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Discussion Starter #1
I purchased my Colorado used, and the previous owner apparently used green coolant instead of the recommended Dexcool. I plan on doing a full flush since I don't know the last time it was flushed. But not sure if I should go back to Dexcool as recommended by manufacturer or just stick with green coolant. What would you do? Could it matter less?
 

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I purchased my Colorado used, and the previous owner apparently used green coolant instead of the recommended Dexcool. I plan on doing a full flush since I don't know the last time it was flushed. But not sure if I should go back to Dexcool as recommended by manufacturer or just stick with green coolant. What would you do? Could it matter less?
I'd go back to Dexcool. Just make 100% sure you flush the system, as those coolant types are not compatible and can turn acidic. The common issues with Dexcool are caused by low coolant, and having excess air in the cooling system. Plus, the green stuff doesn't have that long of a lifespan.
 

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Discussion Starter #3
That was what I was leaning towards, but was wondering if the risk associated with not draining the green stuff completely was worth the reward of sticking to manufacturers recommendations. Thanks for the input.
 

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I have a different opinion on this one . First you can never flush out all the old coolant and as you know the two types don't play well together . This is one time it would be best to leave well enough alone so you don't have a hot mess on your hands .
 

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I had the same exact situation. I did the 500% flush and replaced it with DexCool. You obviously have to be thorough, but its very doable. I popped off the heater core hoses to help flush it out. Hose in the radiator on a medium flow and just let it flush itself out with the engine running. Just like winterizing your boat motor. Once I got the whole system running clear, I let it drain as much as possible and then refilled it with distilled water. Drained it again and started putting some 100% DexCool in. Then its just trial and error to get to your 50/50 mix. The system burped itself pretty well, so no drama there.

My tap water is pretty darn good, but I still use distilled as much as I can. Though I do not sweat having some tap grade in there. I preferred having the GM recommended fluid in there, and I like the longer life.

Before you get the job started, check all of your hoses and clamps (and rad cap) so you can order any parts you want to replace while making a mess. Do your best to capture the old coolant so you can recycle it properly. Your third and fourth flush wont have much left in it, but just make sure critters dont get into the run off. That looks like a horrible way to end your story!

Chances are decent that the previous owner used a universal coolant. I think Prestones version is more of a yellowish than green. I am pretty sure that is what was in mine. Most of the glycol coolants are "compatible with any color" according to the bottles. So trace amounts are not going to give you fits. Wait for a real nice day, take your time, and when you think its good, flush it one more time. Have a couple of clear glasses handy so you can compare what you just got out of the engine to clear water. Only drink beer out of a can or bottle for this process, just to make sure you dont get confused.

You are going to be handling a lot of uncomfortably warm things. Keep your leather gloves on, and your mouth closed. :) Its like 3x the pain in the butt a regular coolant change is, so not terrible.
 

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Discussion Starter #7
So your suggesting I run the truck after I remove all the hoses? and did you remove the radiator hoses from the top or below?
 

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Dragon08 lays out a well thought plan , but in the end if successful all you did is change the coolant color from green to orange . Yes , the chemical make up is different , but in a GEN 1 truck it won't matter squat . If I learned one thing about automotive repair don't create a problem , enough of them will find you . Good luck , whatever you choose to do I hope it works .
 

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Nothing wrong with going back to Dexcool at all, you just have to be diligent about getting it flushed and changed out at the end of it's lifespan, roughly 100k miles.

Good luck with the flush job and for God's sake, do not handle that spring hose clamp with your hands, use two pliers!

I'm just glad I still have my hand after a mishap with that hose clamp and it's still in one piece, yeeeesh. facepalm

Good luck!
 

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Discussion Starter #10
Thanks. In the middle of getting it done atm.
Ouch! I've never even bothered to mess with those clamps by hand. Always assumed I was too weak anyways.
 

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Get yourself these, or something similar:
Totally worth it. Those larger spring clamps are a bear with pliers or channel locks. Can be done, but these make it better. I still managed to bruise a finger tip by mishandling the clamp. I don't remember exactly what happened, but I am positive it is precisely what Colly did too!

Im sure there are smarter videos on Youtube. But what I did is:

Disconnect the overflow bottle and drain it. Fill and drain it several times to get the old coolant out.

Unhook the lower rad hose. Let the coolant run out. When it stops dripping hook it back up and fill the system with clean water.

Disconnect the heater core hose closest to the engine and let it drain.

run the hose into the radiator

Run the engine and set the heat to full hot so you get flow going through the heater core.

Water will be running out of the heater core, careful it will be hot. It should be being replaced by the hose but keep a close eye on your temp gauge at all times. Run it like that for a few minutes.

Stop the engine, and the garden hose. Hook up the heater core again. Top off the radiator and let the engine run like normal for a few minutes.

When you are sure the thermostat is open and you are getting nice hot air from the vents, shut it off and start over. Unhook the lower radiator hose (Careful it is 190* now) and drain the system..

Rinse and repeat until you are satisfied with the clarity of the water coming out of the system.

Then your last refill will be with distilled water and undiluted DexCool mix. There will be some straight water in your heater core and engine, so filling the system up now with 50/50 will leave you on the shy side. Its a guesstimate. My first gallon going in was 75% coolant 25% distilled. Then I added 50/50 from there. Run the truck for a few minutes to get it all mixed together. Then let it cool for enough time to allow you to safely remove the radiator cap. Use your hydrometer to assess your mix. You will be pretty close, but you can siphon off some coolant mix from the rad (put that into the overflow) and add water or undiluted Dexcool to refine the mix. It may take a couple days to dial it in.


Just be super careful with those spring clamps and the hot water. Wear protective gear, and protect the environment.
 

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Now I remember! I had the spring clamp locked open and I was messing with the tabs and the F'er snapped closed. Yeah that stung
 

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Discussion Starter #14
I'm working on the 3rd flush now. The second looked pretty clear. But gotta let the engine cool for 30mins.
I'm concerned about the final fill up of dexcool at this point. Even after running the truck for nearly 20 mins at 2500 RPMs (then turning the heater on when the engine is hot), the engine doesnt suck in any more water to allow me to put more. I'm concerned that when in filling up with Dex, I'll have the same problem and thus have more air in my system than I should.
 

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Discussion Starter #15
I'm currently filling up the system with 2 gallons of water (including the reservoir) when it should be more like 2.5.
 

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Squeezing the upper hose helps move air out of the system too. IIRC there are no bleeders on the engine. So you just have to let it find its way. I remember squeezing both the upper and lower hoses to get it burped.
 

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Discussion Starter #17
People like you make this forum so damn helpful. Went and tried squeezing both and I could hear the radiator burp. Appreciate the help.
 

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You will get most of the air out that way. And get your forearm workout for the day. With that you should get enough coolant into the system that running the engine will force out the rest and the overflow will bubble. Then when the engine cools, the radiator will draw coolant from the overflow. When the engine is cool, and the radiator is full - the process is complete. Then just set the level in the tank to the line and its done. That of course applies to the last fill with the new DexCool batch.

It is tedious doing the flushes since you are switching coolants, but this is the extreme process. Next time you will just dump the radiator once and let it drain out. Then refill with fresh 50/50. If you are super into it, you dump it a second time the next weekend to further dilute the old stuff trapped in the core and block. GM says the DexCool is good for 5 years, and I have found that to easily be the case when the system is clean and sealed.
 

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Discussion Starter #19
342357

What you all think? The three bottles to the left are the last three flushes. The bottle to the right is leftover distilled water.
 

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My rule is out with the dexcool, in with Peak. Buy the straight stuff, mix with distilled water yourself. Over the decades I have learned if you stay with dexcool, you will be changing more radiators, water pumps, thermostats, and heater cores than if you go with Peak. Zerex is a no go for me also. Dex death is a real occurring phenomenon, so I have better things to do with my time. Besides, I have enough old dex death radiators behind the garage. Oh, and in addition to cores, we now have the plastic end caps to be concerned with, so remove and install hoses at the radiator with great care.
I am also not so in favor of really extensive flushes - get out what you can, refill that amount. Repeat every couple of years. I consider this a "Kinder and gentler" flush, IMHO.
It's your ride, do as you wish, but this works for me year after year, vehicle after vehicle.
 
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