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Just wanted to bring something up that I overlooked after getting my engine swap completed. I had forgotten about dexcool being the coolant used in the original yukon cooling system. My swap 5.3 was pretty much drained (I thought) when I got it and after installing it I filled the cooling system with a couple gallons of new green prestone and distilled water. After the initial startup the coolant mixture looked good and I put the cap on and moved on to other stuff.

I opened the radiator cap last weekend and was shocked to see the nastiest foamy red crap in the radiator tank. It appears there was enough of the dexcool crap left in the block that mixed with the Ethylene glycol and it turns to goo that will cause blockages later. Ended up draining and flushing the system several times once with prestone flush and then a couple more times again with a simple green and water mixture. I removed the thermostat from the housing so water would circulate and ran it through several warm up and cool down cycles, draining it after each cycle. I also found that the heater core would not flow coolant either until I back flushed it, it was full of red sludge. In the end I had everything flushed, thermostat replaced and the radiator looked like new again with nice green antifreeze.

Red and green antifreeze can't be mixed, they are incompatible and will cause a gooey messy sludge. Just remember if it had dexcool in it to completely drain and flush your block well before adding coolant. I knew better but just assumed there wasn't much left that would cause an issue. Anyway I hope this little tidbit will help somebody else, lots of info available out there about how bad it is to mix these two, and it seems to happen a lot.

Jeff

Yeah, mixing those is not good.

Why didn't you go back with dexcool? It is a superior product.

Stuka wrote:Why didn't you go back with dexcool? It is a superior product.

As far as I know, it shouldn't be used with copper or copper/brass products such as radiators or heater cores.

I debated going back to it, did a lot of googling and read a lot of the pros and cons of both. In the end more people seem to despise dexcool more than like it and I just decided to go with the old product. I think that with a clean system, new radiator and coolant I should be good for a long time. I will say I learned quite a little bit about coolant with this little goof up.
Of all the LS swaps I have read about I don't recall anyone warning about the issue and I'm sure it's happened a lot.

The shops I've worked in all use the "mix with any" to avoid this. Its the same price as regular, and you dont get any surprises if you miss a little. I wont buy anything else.