ok where to start... ok here we go I live in Indiana and just bought a 97 burb that lived all its life in AZ/NV/CA until I bought it from a guy that shipped It here. anyways I noticed that the temp gauge driving down the highway at 60-70mph stays at 210 and when you slow down and stop it creeps up to 220 or a little higher. put it in N and rev it up a little the temp comes back to 210. and also the rear heat sucked actually there wasn't any heat. the rear heat lines were plugged so I unplugged them flushed the system really good and replace the coolant with yellow(MIX ALL COOLANT) replaced the stat with 195*. had good heat when we did it now the heat isn't HOT HOT but its hot and the rear heat is just cool. and the temp gauge is doing the creep up when you stop at a stop light again. im lost on what to do. any and all help would be appreciated. need to get it fixed soon as its winter and we are adopting 3 boys next month and cant have babies cold in the mini bus!!

 

First of all...
You should verify that actual temp, with what your dash gauge is telling you.
Use a Digital or Laser, get things totally warmed up, then check the return (upper hose) to the engine. That's the point where the temp should be right.
If you don't think you actually know how to do the above, say so, and I'll go into detail.

On the poor heating...
You probably did a good job on the Flush, but, it sure sounds like you have trapped Air back in there somewhere. You could try putting a Vacuum on the System, and see if that helps. If you don't have the equip to do that, a Radiator Shop can help you out on that.

 

do you know if there is a rear blend door? I have a buddy with a 98 2500 6.5 burban and he said in this cold Indiana temperature his front heat will run you out of it. mine isn't that hot. it gets warm and comfortable but not HOT... also his has like 580,000miles and stock front heater core (he bypassed his rear heat and ac)

 

No, I don't know how the 97 blends/regulates the rear temp.

 

Raymon, welcome to the forum. Sounds like you got a nice vehicle, just some minor problems. 1st things 1st, GM engines do better with Dexcool over any other brand which seems to sludge up. You just eliminated some of the crud when you changed the thermostat/coolant.
I'm betting on one of two things wrong, Radiator or fan clutch. I would first block off the grille area in front of the radiator, let the engine idle, watch the temp gauge, when it starts to rise above normal, see if your clutch fan starts to roar, if it does, it's ok. If it doesn't, go to a place that sells AC DELCO, get the same clutch you have. It will have two letters stamped on the front fin & coil side. Don't let the parts store convince you otherwise.
If it's ok, flush your radiator, take TOP hose loose, let that water just go on the ground, stuff a rag where you took the hose off, put the water hose in the top of the radiator, turn it on slow after you start the engine. When the water is clear that comes from the disconnected top hose, your done. That's how you flush the system. Put new Dexcool (red) back in the system. If you still have a problem, replace the radiator. Been there done that, that's why I'm helping you. Good luck,
David g.

 

I have had this happen. You need a new HD radiator and fan clutch. The stock rad barely had enough to cool it. My 3/4 ton truck eventually did the same and no amount of flushing will cure it.