Replaced squealing water pump. Refilled the cooling system slowly and ran at idle to bleed the air out of the cooling system. Now the engine overheats. Seems as if no coolant is being pumped into the engine. Is there a preferred method to bleed the air out of the cooling system? Could the thermostat have gone bad when replacing the water pump? Doesn't sound likely. Any help is appreciated.

 

There's nothing to burp or bleed. That's something reverse flow engines, like the LT1 requires.
Your water pump sucks coolant from the lower radiator hose, pumps through the block, up and out of the thermostat (when it's open), through the upper radiator hose, and dumps into the top of the radiator. As far as air, the only thing you could end up having is a low radiator level. It could be a coincidence that the stat decided to freeze shut, strange things do happen. And speaking of strange things happening, workers behind the parts counter have been known to screw up orders. Check to make sure you used the right water pump. If they gave you a reverse rotation (serpentine style) water pump, that is your overheating problem. Physically, they look the same, and bolt up the same. But they don't pump the same because the impellers are facing/angled in the opposite direction.

 

Thanks for your reply. I am going to replace the thermostat this weekend and give that a try. I drove the car for about 10 minutes and the temp light(no gauge, just a temp light on the dash) came on. When I stopped the car, coolant poured from the overflow hose. Would it be advisabe to test it without the thermostat in? Also, if I let the car warm up with the radiator cap off and monitored the flow, would I learn anything from that? What would I expect to see? Thanks again.

 

Running without the stat won't hurt the engine. Sometimes that can make an engine run hotter, sometimes not. It's a crap shoot based on what the engine needs to keep cool, and the efficiency of the radiator.
Run the engine up to temperature with the radiator cap off, and expect to get a messy overflow. The coolant will expand right out the top.
Did you look up what type of water pump you put on? It's way too coincidental that you now have an overheating problem right after a new pump. I'm still suspicious of that.

 

Sounds like your thermostat is stuck in the closed position.

 

Yes, I checked the specs of the pump. It is a standard rotation pump. The model is NAPA 43101.

 

As stated on the box. But what if someone somewhere got two different pumps mixed up. The one you got I'm sure is a rebuilt. See if there is a part number cast on it. Many rebuilts start life as a factory original, and it may have a GM number on it.

 

That statement is so wrong it's almost hard to read.

 

Looking forward to hear how one "bleeds" a conventional flow cooling system.

 

I have found that the standard rotation pump will have one bolt pattern on the snout and the reverse flow ones will have a different pattern. If your using a factory fan it will eather bolt up or it wont.