Hard to say. But your partial drain was not an adequate coolant service. You drain initially just as you did, then refill with water (heater controls on) and run the engine until the thermostat opens. Let it cool enough to repeat the drain process. Continue to do this (drain, refill, run, drain, etc) several times until the water runs clear and all the old coolant is flushed out. If its been more than 3 years since your last flush, then you should add a radiator cleaner to the water and follow the instructions on the package. Your last flush after it runs clear is best done with distilled water, then drain. This leaves distilled water in the block. Look up your cooling system capacity. Then add enough quarts of pure coolant to the radiator with hose attached to achieve a final concentration of 50%. If there is still some room left to go, fill the rest with more distilled water. You want a final concentration of 50 to 55%, no more, no less. Do the same for your overflow tank. You can buy distilled water for 69 cents or so a gallon at Walgreen or Walmart. Get several jugs.
The old dexcool does not play well with others and is extremely sensitive to air in the system. You can see what it does by putting some in a peanut butter jar & bubbling air into it with an aquarium stone & pump. It turns into a nasty yellow-brown solid overnight.
I recommend starting over and devoting enough time to do the job carefully. I suspect that your antifreeze concentration is too high because you replaced 50% coolant with 100% coolant.
BTW, I devote a day to do this. There's a lot of waiting around for the engine to warm up and the thermostat to open and then time wasted waiting for it to cool down enough that you don't burn yourself (too badly) - so I'll schedule other jobs around this. If nothing else, its a good time to clean the garage.