Draining or flushing coolant?

[StatutoryAPE]

Hey guys. Looking for info on how to properly perform a full coolant drain/flush. The videos I've seen on YouTube only show draining the radiator. And searches I've done haven't shown much about flushing out the engine and heater core as well. Word to note: radiator hoses, heater hoses and T-stat were replaced by a AAA shop about 2 1/2 - 3 years ago when one heater hose failed. I asked them to just do them all since it was already drained and they could do the work for minimal extra charge. Anyway that being said, the Tahoe is mainly for my wife taking the kids to school and driving around town. It's only done 2 long roa trips since that work was done. We do have 2 big road trips coming up for the holidays, one being Phoenix AZ to San Antonio, Austin, Dallas and then back to Phoenix, and I'm thinking this should probably be done before that trip. Any info would be great. Thanks in advance.

 

[Doubeleive]

if you going to do it yourself then park with the rear end up at slight angle or maybe use a jack to lift the rear end just a little, remove the lower radiator hose and the reservoir cap, let it drain, after it has drained you can squeeze the hoses a little or even crank the motor a couple turns. put the hose back on fill with just water, (optionally you could also add some citric acid-radiator flush), let it run a little bit, pull the hose again and let it drain. put the hose back on, then lower the rear back to normal and lift the front a little and fill it with a mix of 50/50 coolant/water, when it looks full rock the truck side to side a few times, start it up, turn the heater on hot and let it get up to normal temp, as it is running and warming up keep adding coolant (as needed) until it is running at normal temp and reservoir is full, put the reservoir cap back on. done. if you want to make extra sure drive it around a bit then re-check the coolant level.
**technically I guess you should use distilled water for the 50/50mix but that's hardly ever done and appears to make no difference

**the next best method is to take it to the dealer, let them do it, they have a machine that sucks all the old coolant out and replaces it with fresh coolant. it's generally about $100. service.

 

[Geotrash]

When you remove the lower radiator hose and drain the coolant out the way Wes suggests, you will get about 13 quarts out of the system. It only holds 15.4. Given that your last cooling system service was less than 3 years ago, and assuming that they changed the coolant then instead of reusing it, a simple drain and fill will be fine. Flushing the system with acid or water wouldn't bring you any significant benefits. Note also that Dexcool has a 5-year, 150K mile service life, so the old habit of flushing the cooling system of your car every 2 years like we did in the 70s and 80s no longer applies.

 

[avalonandl]

The LS engines -which you have - sometimes need to be BURPED. IE tto keep and air bubble from forming in the system. Google is your friend.

 

[Bill 1960]

Acid treatments and vigorous flushing is called for only in neglected systems which yours isn’t. I agree with previous posts just drain and refill and you’re good to go.

When I did mine I had no service history so I drained it and filled with distilled water only and just drove it a couple of days. No evidence of heavy scale or rust in what I drained so after that I just drained the water and replaced the coolant.

 

[13UpInSmoke]

Just did this on my Denali & flushed with distilled water about 4 times I think with a radiator flush in the first two flushes, ran the heater on full blast every time to make sure it circulated through. Just unbolted the thermostat housing vs taking the hose on & off. Removed the actual thermostat during all the flushes & then replaced both hoses, thermostat, & water pump to finish it

 

[StatutoryAPE]

Thanks for all the great replies guys. Much appreciated.