99 Camaro, 3.8, 168k miles, standard

After inspecting my antifreeze levels the other day i noticed some brownish white gunk building up inside the radiator and especially on the radiator cap. I assumed this was a sign that i needed to flush the system and install new antifreeze. the last time i flushed the system was 4 years ago and 68,000 miles. I went ahead and bought the radiator flush kit, peak-"super cleaner and flush", and a jug of dex-cool antifreeze. I flushed the system and used the cleaner but the brownish white gunk is still there. it doesn't seem to have effected it at all. i noticed that the gunk floats and has the properties of oil in that when you rub it between your fingers its slippery like grease and when you try to wash it off your hands the water beads off like oil. so I'm assuming this all means the problem is a leak in my head gasket and I'm planning to replace that however I'm wondering how I'm going to clean the gunk out of my cooling system now? any suggestions or comments would be very helpful.

 

I have the same issue check out my thread "oil in the antifreeze" posted the other day, Some very interesting information.

 

Sounds like someone used some stop-leak in the coolant system at one time, or you didn't back-flush the system by putting a water hose on the upper rad hose and letting it drain through the lower rad hose. You need to flush your engine block as well as the rad.

 

I've never used stop-leak and i did flush the entire system with the flush kit by installing a T fitting onto the inlet hose to the heater core allowing me to flush the entire system with my water hose.

 

Not a good sign, If it feels oily, then some foreign substance must be getting into your cooling system. If you didn't add any stop leak or similar item, then maybe oil is getting in.
Ck for gasket leak, cracked head, etc.

 

antifeeze will feel like oil. are you seeing any coolant in the oil? are you losing coolant? do a pressure test on the cooling system and see what happens. i agree with freeze it sounds like stop leak.

 

Well, then your rad is really sludged up! In such a case, you need to disconnect the rad hoses and then plug them. DO NOY USE ANYTHING CHEMICAL OR ABBRASIVE! Pour about 1/2 a jug (2 quarts) of vinegar into the rad and let it sit for a few hours. Then drain it and use a garden hose to flush it out well. Use the pressure of the hose to flush it out of the lower rad hose. Screw in your drain plug and flush out through the lower rad hose because sludge can't fit through the drain plug.

If that doesn't get rid of the sludge, then you have oil leaking in your system or you need a new rad.