What about opening the drain on the block to get a better flush? Someone somewhere posted that they took out the knock sensor and ran water through the block to flush out particulates and goop that settle there.

I was reading my 03 manual and it talked about flushing by filling with water, running for 20 minutes to mix and stir, filling, repeat. And then fill.

I always have a lot of water reaining in the block and bottom of radiator because I just take off the lower radiator hose. I put in the 6 quarts of DexCool pure and then add water to fill reservoir. The 6 quarts is hard to get in because not all the water is drained out.

HOw do others drain theirs?

If you are just draining and refilling, then removing the bottom rad hose is sufficient.

If you are wanting to do a complete flush then I recommend getting a flush kit which will actually circulate and truly flush the whole system. That'* the best way, IMO. Just make sure you follow all directions. For example, blocking off the heater core so it doesn't get plugged and fail.

Depending on your financial situation, you might consider taking it to a shop and let them flush it. They'll recover all the old coolant, refill it, and it'll be as clean as you can get it. That'* how I did it, then when I got it back I checked everything out to make sure they did it right because I'm so anal. Just another option for you to consider.

If you want to drain the block as well, you can remove a knock sensor. I used a deep socket and about a 6" extension and got the back one out in about 5 minutes.

i drained out the old coolant, filled it with water, idled for about 8 mins with the heater on (to circulate coolant thru there)...then i ran a flush chemical thru it, flushed that out, and then filled the radiator with a gallon of prestone dex-cool, then topped it off with water...the gallon of pure coolant makes sense, cuz the engine and hoses will aleady be filled with water...it all balanced out to a good concentration, i tested it with a coolant tester (you can buy them for about a dollar). i know this process is a pain in the butt, but it saves money from taking it to a shop, and also, you know what you're doing to your car.

by the way, i know the topic of dex-cool being total crap and not belonging in any of our cars comes up a lot on this site, and i know the reccomendation (usually from willwren) is to use "prestone dex-compatible coolant"...i've found that the prestone extended life fits into that category as well...so my question is: should we use the (yellow) extended life formula or the (red-orange) stuff that specifically says dex-cool on it? is the prestone dex-cool just as evil?

[quote="nicklikesmilk"]i drained out the old coolant, filled it with water, idled for about 8 mins with the heater on (to circulate coolant thru there)...then i ran a flush chemical thru it, flushed that out, quote]

What kind of flush chemical do you use...

In the 03 manual GM just says to fill with potable water and run for 20 minutes and drain and repeat and drain. Then put in coolant. I wonder if any flush chemical other than the mildest over-the-counter stuff would be safe with the various seal problems???

Input anyone?

i used prestone super radiator flush...the basic stuff

still pondering the prestone dex-cool vs. prestone extended life...anyone have info on that?

You'll find knowledgeable people on both sides of that debate. Some say go with the Prestone Dex-compatible, and others, myself included, feel staying away from anything Dex is the way to go, and recommend the "all makes/all models" G05 type coolant.

Series II engines have two knock sensors located in what would have been the block drains for each bank. To completely drain the coolant, you would need to remove both of them. They are not easy to get to, not easy to remove, and must be carefully re-installed so that the threads provide a ground but still seal against a coolant leak. The tightening spec IIRC is 12 ft-lb. I only remove them to completely drain the coolant when the engine is out of the car.