overheating

While driving to work today my temp gauge went to the max, so i pulled over and checked all the obvious things. Oil is fine, theres coolant both in the rad. and the overflow resevioir, and the fan is switching on. I did notice alot of gunk built up on the underside of the rad cap and on the fins of the rad. My question is where do I start to diagnose this problem....thermostat? cooling system flush? heater core? Cash is definatly an issue so Im hoping its not serious. Ive read on here about the evils of dexcool and the systen flushes seem to work wonders...So any Insight is greatly appreciated.

Welcome to AF.
There is no more evils with Dexcool than old green.
Both need coolant system service.
Start with the stat and a flush with new coolant.
And make sure it is actually getting hot and not just the gauge.
MT

if it went to max you might be in some trouble like head or head gasket. but i'd try what he said about thermo and flush...good luck......

The temp only went to the max for maybe 1 minute. I immediatly pulled over and let it cool off, So I'm hoping it didnt do any permanent damage. I can drive it for the time being with the heat on full blast. When I do this the temp stays raised at about 235-240 but not pegged out. I will buy the flush kit and therm on friday when i get payed...any suggestions on the best kit to use to flush all that gunk out?

I figured out the problem....there was a couple of cracks in the intake manifold gasket that was allowing air to enter the cooling system, thus turning the coolant into sludge. So I changed the gasket, flushed the entire system several times, changed the thermo and rad. cap for good measure and back flushed the heatercore, and all's well.