Types of coolant flush

It's time for a new water pump in my 04. When I had my 1997 vortec, I had a very neglected cooling system. I mixed and ran citric acid in the cooling system to help get the rust out (heater core lines clogged with rust scale). Then a clear water rinse, followed by TSP to get the Dexcool sludge out. Then a clear water rinse, and disassemble. Once the pump was off I sprayed the hose directly in the block to loosen more sludge then compressed air to get as much water out as I could and reassemble.

I am not as familiar with the 04 system. I don't seem to have a rust problem, but is there an issue running water and TSP? Can I connect the heater core hose flush fitting on this system?

Just make sure to use distilled water and not tap water. I have never used "standard" chemicals and always spent a little more and picked up the stuff designed to flush out the system. If you pour in the standard chemicals and it isn't the correct strength you can either do damage to the system or not do enough cleaning. With some chemicals this is not as much of an issue as with others. I believe pretty much everything is copper or aluminum so don't believe is prone to much rust. Especially if you have always had good coolant. If you put products in your system to remove rust you may remove more than rust and cause a leak.

Note these are all personal opinions based on past experience using chemicals in a laboratory and may not apply to automotive usage.

But I do stand by the use distilled water for all functions and never use tap water. Tap water is generally corrosive from its additives and most tap water uses phosphorus to coat piping to prevent lead leaching out of old pipes (See city of Flint for what happens when they don't) So always use distilled water. (Spring water just means it is ground water and even if filtered can have most of everything that tap water does.)

I always just flush as best I can with distilled water up front to get out as much as I can with just flushing to allow the radiator flush to work better, Once flushed then run with the radiator flush to get as much as possible, flush again with distilled water to remove all dissolved gunk then drain as much as I can, put in my gallon or so of full strength coolant then top off with distilled. If cold out then I let that run for a while so it mixes well. All with the heater on full.

No argument there, I use distilled water every time. Just boil off tap water to see what junk is in there. So can I use the heater core flush fitting on these newer cooling systems? If I was to go with a product instead of TSP for cleaning sludge, what would you suggest?