So I back-flushed my heater core this weekend. Its a procedure I've done succesfully a few years ago also.
Issue now is the temp now runs with the needle straight up (212?). Its always previously been at the first mark or slightly above (180 deg.)
As I've done this in the past....system has been bleed, only coolant coming out the bleeders. No trash on the radiator. Fans all working.

If I'm at a light and start from the light and bring the revs up as accelerating the temp will drop to normal for a bit before rising again.
Only thing I can think of is I put too much water and not enough coolant when refilling?? Any thoughts or help!

 

Hmm sounds really like bubbles in the system... but you said they're all out. Check the radiator once its cold, perhaps it needs a few cycles to get all the air out....

 

Checked the radiator once after it cooled and it was topped off. Here's how I did my bleeding with a cold engine.
Opened both bleeder screws....Filled radiator very slowly to the top,
Started car...fluid came gushing out the radiator instantly....put radiator cap on to prevent big mess.
Car heated up....continued filling coolant through resorvoir until bleeder screws flowed coolant out. Closed screws, checked coolant level.

After driving home tonight with a hot car, opened both bleeder screws and coolant flowed out, level in resevoir is correct. Additional ideas?!?

 

It sure sounds like your pump is not always flowing as it should. This can be caused by low coolant/air pockets, or a problem in the mechanical parts of the pump or pump drive. Since it happened right after a refill, it is probably just not filled all the way.

Your fill proceedure is not right IMO. For one thing, you can't directly fill the system through the overflow tank - the overflow tank only adds coolant to the system when it is cooling down. The contracting coolant pulls more fluid into the system as it cools down, so if you run the car through enough hot/cold cycles like this, and keep the overflow full, it COULD eventually result in a good fill.

Also, I never use the bleeders with the engine running. I fill it as much as I can and make sure coolant comes out the bleeders, close the bleeders, cap it, run it for a short while but not enough to get hot, then repeat until the radiator stays full. Then, after a thermal cycle, I check the radiator level again cold and top it off.

You will probably need to push down on the 'mid hose' bleeder to get it low enough to let coolant flow out when filling.

Shoebox has a slightly different fill proceedure on his site, but I have had coolant gush out while running it with the cap off, so I elect to do it as above. I have a bleed hole in my thermostat, so I don't need to wait for the stat to open to bleed the engine. I don't remember if the stock stat has the bleed hole or not.

(EDIT: I just looked at my old stock one and it does NOT have a bleed hole. You can drill one to make filling simpler, it's just a 1/16 or so hole in the 'valve disc'.) But Shoebox's procedure is probably best with the stock stat.

See 'How To' #14 for Shoebox's process:
http://shbox.com/1/4th_gen_tech1.html

 

Could be then..
Therefore... once car is cool I need to open all bleeder valves, fill through radiator until nothing but coolant comes out bleeder valves, close bleeder valves.
Run engine with radiator cap off and wait till thermostat opens and fill to top of radiator?

I remember trying to do this in the past and I can't ever get the bleeder valves to emit coolant without running the engine. Aren't the bleeder valves ABOVE the top of the radiator thus preventing fluid from ever coming out of them before the radiator is full??
Every time i'd run the engine without the radiator cap installed it would just start to overflow. Maybe i'm crazy!

 

Well, mine overflows with the cap off, too, so you are not crazy. I never got that to work either. You can also cheat, and pull the stat out to dump coolant in the engine directly, but it's a little low to fill all the way. If I were you, I'd just drill the bleed hole, too.

Another possibility is that the pump drive is starting to fail, mine did and I had 'hot spells' at certain RPMs that initially would go away if I revved it. My splined shaft was stripped. With the stat out, you can try to spin the impeller my hand. It should not spin. Careful not to cut yourself like I did, the edges are sharp.

Good luck.

 

Well just went out and did the "shoebox" fill method. Dumb me, with the top most bleeder screw open and running the engine with the radiator cap off...all the coolant overflows. Therefore here is what I just did.....
With both bleeder screws open the lowest (closest to thermo) bleeds out and I closed it, still can't get top most bleeder to bleed just filling radiator. I filled the radiator to the top, closed all bleeders, let engine warm up (past first mark), no drop at all in radiator fluid, closed radiator, filled resevouir.

Went for a drive and still no change, still runs warmer than normal. I don't see how you can bleed to top most bleeder screw when its above the radiator w/o engine running.

One final update. Went back to garage and started warm car. Opened upper bleeder screw and it blew out a lot of air before it finally turned all to coolant....hoping now that its fully bleed.

 

Yea, I think leaving the lower bleeder open when running must suck air IN, thus pushing coolant out. Sounds like you are on to something with 'hot bleeding' the upper bleeder only to purge air. Glad you are figuring it out.

I also like to fill the rad with a funnel. If it fits well, you can overfill it so the coolant level goes higher than the bleeder. Sorry I didn't remember earlier. Last time the front of my car was on stands, so I didn't need to do that, and I forgot about it until you mentioned the elevation issue.