G/F's Blazer has been acting up lately. Here's the deal.

96 Blazer by the way, Its got air in the coolant system, but planned on getting a flush. Every once in a while at idle or a stop light there would be no heat. Once you get on it there would be heat. Odd eh.
Today the durned thing almost overheated, but I noticed the gauge and cranked the heat on full blast and the gauge went back to normal. Now its a regular occurance, so I'm assuming that it needs a new thermostat correct. Any oppinions on this? By the way its using the red stuff.

 

Is the upper rad hose hard after a bit of driving? It's supposed to be.

I would start w/ replacing the T stat and rad cap. A flush would be good too.

I just replaced my T stat/rad cap recently at 79,XXX miles.

 

It sounds like you're just low on coolant. Make sure everything is topped off and see if you still have overheating problems.

 

I Topped it up and its good to go so far. Bought a t-stat for it anyways, not changed yet. also bought a new rad cap for it and the idiots at the parts counter gave me the wrong one.[:@]