I'm about to be changing the radiator hoses for a friend. Is there a cooling system air bleeder screw for this car.......what is the proper way to purge the air? Is there a fsm on this site? 1998 Bonneville....I believe it'* a 3.8 v6

Depends. Which radiator hoses are you replacing?

Upper hose-just add more coolant mix to radiator.
Lower hose-you may be able to just do a top off and be ok.

It really depends on how much coolant you lose.

If you drain the cooling system, this is what I do, never had any problems. Remove the thermostat, and fill the system threw the thermostat hole until it'* full, the place thermostat in and put housing and hose on. Then fill the rest of the way threw the radiator cap. You may end up with some air in the heater core, so you will need to check level.

Learned something new today. Thanks Dan!!

I always just topped the radiator off, started the car and massaged the lower hose until I seen coolant coming through the bleeder.

Doing that removes the air trapped under the thermostat.

There is an air bleed screw in the top of the thermostat housing. The GM FSM states that you should fill the car and start it up. Open the bleeder screw and let it bleed until a constant stream comes out.

The reality is ... the method Dan mentioned works better than opening the screw.

And me.. I don't fill through the T stat or crack the bleeder unless the system seems air bound. I fill though the rad, start the car and fill as needed until the engine reaches operating temp and opens the thermostat. Then put on the cap and overfill the coolant overflow a little bit. 1 out of 100 times I'll have an airbound one. Usually cracking the bleeder works well. If not.. I pull the stat and fill there.

When i did my LIM gasket swap sunday, i refilled the radiator through the radiator cap. 15 min down the road temp gauge spiked. I pulled over opened up the bleeder screw. Restarted the car temp gauge immediately went back to normal, and it * been fine ever since. So the moral of the story, get the air out.

When I replaced my LIM recently I took the thermostat out and drilled a small hole through the thermostat like this

The hole doesn't have to be this big, just big enough for air to pass through when coolant pushes it out. If you make a hole too big you will have issues warming the car up.

By doing this it makes it a bit easier to bleed the air out of the cooling system. You should still squeeze the hoses a bit. But when you finish refilling the system, go for a drive. Let it cool off for a while then top off again and you should be good to go, just keep an eye on the coolant level for a few days.

I didn't read this thread prior to re-filling my coolant system and now have air trapped in. I got the car up to operating temp and opened the bleeder screw. It looked like a tea kettle blowing steam with intermittent squirts of anti-freeze. I let the car run for darn new 15 minutes and it never shot a steady stream of anti-freeze. I can't see there being that much air trapped in the system.

Note: Just replaced the water pump and filled er back up with coolant.

Update: This site has been amazing this weekend in helping with my water pump replacement. Just when I seem to have hit a dead end I fine the answer on here!!!

Note: I had a cooling system full of air as described in the post above. I had everything topped off and from what I could tell the cooling system was topped off. After letting the car cool off for a while I went back out and opened the radiator cap. the coolant was now low and the over-flow res. was empty. I pulled the thermostat housing off and filled it up as described in this thread. I then filled the radiator and as it filled it would bubble. Once topped off I filled the Res. to it'* required level and started the car. Once the car was up to operating temp I opened the bleeder screw and a nice constant stream of coolant came out with no air or pulsing. Took her for a test drive and everything is functioning perfectly.

Hope this helps someone down the road.

Thanks,
Steve