thermostat stuck? I don't think the heater core is the issue.. What fan are you using? I recently switched from a electric fan/shroud combo to a fan alone and my temp went up a good twenty degrees even though the new fan pulled more CFM, it doesn't cover as much surface area as the shroud did so it makes a difference. Post to let us know whats up.....

GTNBY2

Check the rad flow on a cold engine. If it is flowing right away the thermostat maybe stuck open. 

Going to change that next.  The fan has no shroud so I may look into that as well.  The fan is an aftermarket piece which does move air but as said above, it may need the shroud, so I'm not going to rule that out either. 

I was personally amazed at how hot my car was running after "upgrading" the fan to an aftermarket 16". The one I replaced was a junk yard 4 banger fan and it kept it cooler than this BUT it did have a shroud that covered a good 75% of the rad. This new one sits in about the same place but with the cross flow rad I have it has several tubes not having air pulled across them by the fan. I'm gonna do some sheet metal origami and try to rectify the situation. I've seen some slick ones made on Ebay but I don't wanna pony up the doe....but I probably will end up doing that anyway!!

Ok.  Still contemplating a fan shroud, but not because its still overheating.  I haven't run it down the road since the fixes, so it may be ok.  I replaced the thermostat today.  Also, I found and fixed a couple vaccum leaks.  The other thing I did (and couldn't believe I didn't realize it before) was rewire the fan so that it pulled instead of pushed.  Hopefully that will cure everything 

Never would have thought of checking the fan direction. Good call there. 

Yeah good call for sure..you usually don't think about that or at least I don't !!lol

Well.  Gets hot in traffic (downtown).  Seems fine at speed.  Looks like a shrouded fan.   

Well.......SUCCESS!!!!! maybe??? 

we'll see after the fan install. 

you doing a custom or going back to original? I thought about finding a stock shroud and mounting a electric fan in it... thought that would be cool! 

Going back to stock.  There is a 6 in the local j/y.  Thought I would use the one I have as a pusher too (in there's enough room.  Not sure if I'm going to remote it or just tie into the low speed. 

Psot some pics if you get it all done up....

Ok..  

check water/anti fz. mix, sometimes runs better more/less ani-/water depending on altitude etc. had same problems (why I cut holes in "facia"
on gt.(which did the trick)good fan/shroud (permatex) (blowing the right way,lol)set thermostat low to give time to cool BEFORE it gets hot so it will keep up in traffic.

What about the small flat plastic piece under the radiator? Do you have that on the car?  It's important to the flow of air since there are no holes in the front. When I was swapping stuff I removed mine and did not install the new one right away. made a huge difference in the temp.  

That was my first thought. You would be surprised how many people Ive talked to that put the fan on the wrong direction. so dont feel bad. your not alone. Also what Tim said. That will make it over heat too. Usually going down the road though. If it only does it at stops, I would lean toward a fan shroud too...or a bigger fan. Depending on what fan you have.

Fan is big eough to cover the radiator top to bottom.  The air deflector is broken.  So, I will need one.  At this point I wired it to a switch temporarily.  That seems to have cured the problem for now.  Relaying the switch is in the works, but it does work at the moment.  I still plan to fix it correctly.  I'm not big on half assing stuff.  I want to make it right in the end.  The local j/y has a 3.8  fan in a 95.  Whats the difference?  Its still a 2 speed fan.