Started my ride home from work (30 miles of 0-20mph stop and go traffic) just like any other but about half way there i swelled that characteristic sweet smell of antifreeze. I quickly jumped out and checked around and found nothing and got back in the car. Once parked I popped the hood and found that my resevoir had split right where one of the molded nuts is integrated into it. In fact, upon trying to remove the reservoir the molding that held the nut had partially broken off into the res. I replaced the reservoir and thermostat which had seperated into two peices and had to be retrieved with a magnet. Here's the weird part- when i took the T-stat housing off i had a rush of pure Green antifreeze fall unto my hands.....but on the reservoir side it's a thick dark brown dex cool. ( I intend to do a flush once I'm on the road again...) I have never opened this system before so this is the first time I'm seeing this. How is it possible that the radiator and reservoir and bottom coolant return hose all have dex, but the outlet side of the radiator Pipe only had the regular green stuff?

 

Just an update... my "new" blazer has the same exact problem. Green antifreeze up top and orange in the rad and resevoir. WTF??? I wonder if the orange and green weren't seperated by different specific gravities or maybe the green got added on the vehicles and stuck in the heater core?? This is my 5th blazer since 2004 and 3 of them have had this issue. what's funny is that the only time my trailblazer (2000) was ever serviced by a mechanic other than me was at a GM dealer. The strangeness doesn't stop there. The 5 that i have owned are as follows-

1997 blazer2 door 2 wheel drive........ old rusty dex coolant.....used vehicle46,xxx
2001 blazer2 door 4 wheel drive........mixed,sludgy dex....bought with 48,xxx miles
2000 trailblazer 4 door 4 wheel drive..mixed coolant bought new (serviced by GM only) 101,xxx miles full of sludge from mixing/electrolysis...?
2001 blazer extreme 2 door 2 wheel...green coolant ....2nd owner 68,xxx
1993 gmc typhoon 2 door 2 wheel drive...all green coolant 89,xxx

So my 2 doors had no mixing and good healthy cooling systems, and my 4 wheel drive ersions had either mixing or horrile sludge deposits ( i replaced the rad,t-stat,pump, and core on all the 4 wheel versions).
Are the trans coolers that are built into the radiators that prone to leak?
Are most of the DEX Cool related issues mostly 4 wheel drive?
Does simply mixing the two cause the sludge?