brown sludge in radiater

i have been finding brown sludge in radiator and overflow bottle, truck is 94 burban with 350, 180,000 and the oil cooler in the radiator. no coolant in oil pan. i've asked my buddys and have gotten the oh you blew a head gasket. but i dont think so. i think its the radiator, so how about it guys anyone got an ideas. dont want to pull the heads off to find out it was the radiator. going to remove the oil cooler from engine and flush coolant and try that to see if it is the radiator but anyone got any better ideas?

Hi 84 Fiero: A quick question, did you find this sludge while doing regular maintence or did you notice it because of a malfunction? IE, something broke? My first thought was ignored antifreeze will develop a brown rusty sludge, but I think you maintain your vehicles better than that. My second thought is that something has contaminated the coolant, like a quick leak repair additive, or a deteriorating hose or seal. If the truck is running ok, Id flush the whole system out and replace the coolant mixture and keep an eye on it before I started taking things apart. Its been my experience, its usually the simple things that get over analyzed that create problems...Just my 2 cents............. good luck. Mike :iceslolan

just had system flushed a few week ago, and its even worse now than before, pulled oil coolier lines left radiator hole for oil lines open put hose in oil lines so it buy passed radiator and ran truck to see if anything leaked out of oil cooler holes. nothing. so i know intake is leaking and i have to replace that , going to hose engine off later and keep eye on engine for any other visible leaks, also going to run comprestion test this weekend.