if you know you blead the system and it's still overheating then you have clog somewhere. even if the water pump isn't bad, it would be worth your time to pop it off and run the garden hose through it very well. you mentioned the temp sensor (guessing you mean the one on the block that sends the reading to your gauge?) now would be an excellent time to replace it because crud can get stuck on one side of the sensor. generally just running a hose on both sides of your water pump inlet will clear this out okay. only other thing is at the top of the engine, there is a 3/8" tube that runs from the right (passenger) side of the intake (there should be a rubber elbow that plugs into the throttle body) and it wraps around to the back of the block. I cannot remember what it's called but it's pretty thin and those can rust out and or clog (this normally isn't a common cause). Your heater core however is a very common point of failure for clogs. this will be most noticeable if your engine is warm but your heat doesn't work. you can unplug the two hoses on the firewall going to it and just run the hose through it. the water will most likely be dark brown but you just want to flush it till clear.

For me, I replaced my water pump a long time ago and since then the heat just never really worked great. it took me 10 years to realize that my issue was that I used too much RTV on my WP install the remains just broke off into my cooling system and the heater core is where they stopped. but to answer your question, when a WP goes bad on these cars it usually starts as a squeak or rusty bearing sound inside the water pump and or followed by it dripping coolant from the weep hole all over your opti.

 

I cannot remember what it's called

Steam pipe.

1993-1997 Camaro Firebird LT1 Rear Coolant Crossover Line Pipe w/ Banjo Bolts

93-97 LT1 Camaro or Firebird and 95-96 Impala or Caprice Coolant Crossover Line

www.hawksmotorsports.com

 

This is worth a read. There was a steam pipe on ebay at the time. Looks like its not available at the moment.

Whats the proper way to bleed the cooling system | Chevy Impala SS Forum

 

IIRC 95Wagon mentioned in a thread not long ago that the steam pipe is something one should consider having a replacement for as they were becoming extinct. At that time Hawks did have them, appears not anymore but I did get one form their Ebay site awhile back as I was considering rebuilding my original LT1 into a Carb motor for another car.

Don't think this is OP's larger issue of overheat as that pipe is more a "steam" venting thing between the 2 heads but is obviously a "needed" functioning component of the reverse cooling system unique to the gen 2 LT1 engine

The coupler that connects WP drive spline to WP spline can strip thus minimizing if not preventing WP from turning. If radiator hose does not get warm when engine is running, WP is not working. Removing WP front cover being careful not to break rubber O ring seal and confirming impeller turns when engine is cranked will confirm it still "pumps". Not common impellers come off

 

Have seen some people make their own vent line and they look pretty cool.

 

You can also use the Corvette LT1 crossover pipe, requires a longer piece of hose.

 

Yeah there are alternatives, not sure if Vette one is still available although there are many LT1 engine cars in junkyards. Did see a AN pipe/fitting one someone made. IIRC the banjo bolts for steam, aka crossover, pipe are tapered??. If so retap for another thread/pitch type fitting if its a tapered hole in heads. All doable but more involved

 

Banjo bolts are NPS ( National Pipe Straight) thread. I have found silicone sealer clogging the banjo bolts in junked engines. NPT plugs seal the threads in the front of the cylinder heads.

 

Just removed all the Tow pack stuff and pulled the front cover off the water pump. Just about 1/4" or so of play moving the impeller back and forth. It that normal? Can't remember. Looks very clean inside. I replaced it with a NOS USA one about 7 years ago. Also ran garden hose thru radiator. Flowed out well and clean. Also ran water thru heater core hoses and expansion tank. Seemed to flow well. Not too dirty. Doing this just to try to find out what just the overheat. If it was water pump then I was going to do all the Opti clean up and Cap & rotor and new seals which I just did last year on another B body.

 

Its been over 20 years since I had a mechanical WP (went to EWP) but I would assume there should be 0 play. The impeller should be solidly affixed to drive shaft/spline of WP which is mated to splined coupler that is mated to splined WP drive gear...unless between all of that there is some play normally

If there should be 0 play, maybe your coupler splines are worn causing it to slip under load/engine running??

 

Maybe. Just cranked engine without plugs and pump impeller was turning. The heads need to come off anyway (blown gaskets) so I will just yank the pump and check it out completely and also refresh the Opti and seals behind it.