Flushing coolant system. Best way?

[optimusprime]

I’ve never flushed the coolant on my 08 6.2 Denali since I’ve owned it (5.5 years). Recently the heater hoses busted off and dumped a ton on the ground. I’m going to replace them and the upper/lower rad hoses and thermostat. Do I need to totally drain every last ounce of coolant out or can I just drain the lower hose and add new fluid? If I have to flush the entire system, what’s the best way to do it?

 

[Doubeleive]

I’ve never flushed the coolant on my 08 6.2 Denali since I’ve owned it (5.5 years). Recently the heater hoses busted off and dumped a ton on the ground. I’m going to replace them and the upper/lower rad hoses and thermostat. Do I need to totally drain every last ounce of coolant out or can I just drain the lower hose and add new fluid? If I have to flush the entire system, what’s the best way to do it?

the best way is to let the dealer do it simply because they use a machine that vacuums the entire system out,
other than that just doing it yourself then park it on a slight incline with the nose down or jack up the rear a little, pull the lower radiator hose let drain out, replace the hose and point it nose up a little or jack up the front a little and refill with 50/50 mix. doing this allows all the air out.
my personal recommendation would be to also fill it with water a few times to push all the old coolant out, I also normally throw some radiator flush & water in it as well and drive it a couple days then flush it again.
others may have a different method.

 

[Doubeleive]

and I wouldn't worry about the thermostat, if anything happens from this point it will be a water pump failure or radiator cracking. Thermostats rarely fail anymore

 

[alpha_omega]

x2 on what @Doubeleive said (both posts). If you’re not close to a dealer another option would be to pick up an “Airlift Kit” like this one.

 

[89Suburban]

x2 on what @Doubeleive said (both posts). If you’re not close to a dealer another option would be to pick up an “Airlift Kit” like this one.
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Stop spending my money!

 

[Bill 1960]

How nasty was the fluid; how much corrosion from neglect?

That would determine how aggressively I cleaned the system.

 

[alpha_omega]

Stop spending my money!

Sorry! You guys did it to me the other day. Plus I’ve had this one for a few years. I thought you bought one the last time I mentioned it.

 

[OR VietVet]

I agree with @Doubeleive except for two things. I would most definitely replace the thermostat with:

Thermostat & seal: https://www.rockauto.com/en/moreinf...dw77N6eSIERXO/enkyNPqwzCcHSV8g7JJ2ZXLKY4S52S6

When it is all opened up, I would use your water hose and use that water pressure to flow thru all channels, forward and back or take to dealer for that machine.

By the way, if you ever do the water pump, do the thermostat again.

 

[Joseph Garcia]

Stop spending my money!

??? That's what we do here. It is MUCH easier to spend other people's money, than our own.

 

[OR VietVet]

I absolutely love spending OPM.

 

[Geotrash]

I've had to replace the coolant in my Yukons a number of times for various jobs including cam swaps, new radiator, coolant tees, etc. I never had any problems with air in the system or anything else. Modern coolants are remarkable in their protective properties, and I've never seen any sludge or corrosion debris in any of my cars with modern cooling systems, even after hundreds of thousands of miles. I say put new 50/50 Dexcool in it, and send it. No need to flush. I'd be worried about residual flushing chemicals remaining in the system.

 

[me51]

When I changed the coolant in mine, I just took off the lower hose at the radiator and let it drain out. The service manual says there is a drain plug on the engine block, but I could not find it. The whole system is supposed to take about 17 quarts, and almost all of it came out if I remember correctly. Then I refilled it with a coolant with GM spec 6277M and bled the system which was not too difficult.

It is a very messy job though, make sure you have a kiddie pool or something similarly shaped to put under there to catch all the liquid.

 

[optimusprime]

x2 on what @Doubeleive said (both posts). If you’re not close to a dealer another option would be to pick up an “Airlift Kit” like this one.
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My father in law gave me one of these. I used it to refill my Ford radiator but wasn’t aware I could pull all the fluid out. I’m guessing you can pull the fluid out as well?