Need to Flush

[Donf]

The ole coolant is only about 12 -- 14 years old but I thought I'd go ahead and change it "ahead of schedule" just to be safe.

I've read a few posts online and discovered that a buncha liquid stays in the block after draining the radiator via the drain ****. Removing the plugs in the block looks like it could be a PITA. My next thought was to simply drain, fill and run the car to operating temperature 4 or 5 times and then add the recommended amount of straight antifreeze and top off with water.
But then....
Way, way back in the '70's my dad came home one night with a case (!) of Prestone Back Flush Kits (https://prestone.com/product/prestone-flush-n-fill-kit/). Every car we had got one and received a good flush. A good, FAST AND EASY flush. But i never see anyone mention them in the posts I've been reading.

Thoughts please.

 

[JackFox]

Most vehicles I service tend to hold about 40% of the coolant in areas that do not drain from the radiator petcock... or the lower hose if I feel the petcock plastic is not up for the job of being twisted! So draining the block or flushing is the best 2 options. Some vehicles like toyota/lexus have a dedicated block drain. And the ones that don't, I just fill back up with distilled water and run it till thermostat opens. Usually do this with the lower hose clamp removed and thermostat removed. Then I can just pull it, and drain ito a drain bucket. Put back on. Do it again. And again. run the engine 3 minutes between each flushing.

First drain and fill gets you 50/50 old/new fluid.
second draining and fill gets you 25/75
Third gets you 12.5/87.5 stop here and put new mix in!

Continue this process 5 times if you initially put in some flush to help get crap out. No coolant should be used more than ten years and, you know what as I re-read that I can now see the sarcasm

I do not use the back-flush system. Just the prestone flush fluid in the mini coolant bottles. I use 3 at a time when I do it! But I only care to back-flush the mini-radiators in the HVAC boxes (heater core) as they tend to get clogged on most vehicles anymore these days. Other wise I let the flush chemical do it's job, along with heat and movement. Engine does the heat. Pump does the movement. I let them run for 20 minutes with the cleaner in there. Then flush out with distilled water 5 times over. Then fill with straight coolant.

I sell drain and fills to customers so that they don't have to ever go through the process of flushing and such. ALso, it's a good idea to run your hand over the radiator WHEN YOU REMOVED THE FAN REAL QUICK, when it is running and warmed up. Any cold spots let you know it is getting partially clogged. And just like most car parts these days, they were meant to be throwjn away and replaced! Many chinese units are cheap all over the web. I go with a brand, OSC. They re-engineer many things and give a better unit in most cases.... except for chargers and other vehicles that use the same radiator, like the Fiat-Chrysler 300s.

 

[Donf]

Thanks

 

[Fless]

Lots of great info in this thread, especially the detail from @SnowDrifter

What coolant should I use?

The manual says to use dexcool so that's what I got. However, when I drained my radiator, green coolant came out. I think maybe something universal was added by the last owner. I don't know if it's OK to refill with the dexcool at this point.

www.tahoeyukonforum.com

 

[Eman85]

I pull the block plugs, messy but you know you're getting rid of the old antifreeze. The Passenger side plug is the knock sensor.