GM Water Pump change

[Nitro23]

I decided to replace the water pump while I was doing the LIM on my van. It looked a little different as it has 5 or six blades versus the impeller design. A note in the package said GM changed the design of the impeller and the manufacturer is following GM's design change. I bought it new at Autozone.

It was interesting that when I went to bleed the system, I had very little air.
I also changed by bleeding procedure. I got this idea from the BMW procedure (another one of my toys). I jacked up the front of the car so the RAD was higher than the t-stat prior to adding AF. Also opened both bleed valves then added AF. I filled, let sit for 30 minutes (watched 2nd period of red wings game) then topped off. Put RAD cap on, and never had to add any additional AF in the RAD. Just had to insure the overflow was filled. I did have to add several times to the overflow.

Engine seems to be running cooler.

I think the new pump might have better flow.

[meggabad]

I bought that same pump from AZ and know exactly what your saying about that new blade design. However, I'm curious where to bleed off air on these vans. I had a problem after adding AF at first. Van started to over heat so I just shut off and let sit for a while. I had already topped off the resevoir and could hear fluid tricleing into the system. Started it back up after about 15 min and everything was fine. However, when I get my motor back together, I'd like to know exactly how to do this so I dont chance screwing up anything from overheating. Thanks.

[Nitro23]

The 2 bleeders locations are 1) on the bypass pipe above water pump. This pipe goes aroung the fron tof the motor to the intake (2 hook ups) and back to the heater core. 2) on the T-Stat housing that the Upper Rad hose connects to.

You will have a lot more vapor/air in the system if you replace the heads. But when doing the LIMG it should be minimal. Jack up the front and open bleeders prior to filling.

[merc81]

I found (by accident...) that if you replace the bleeder beside the water pump with a mini brass valve (home depot/lowes), then you can slide a rubber hose over that valve outlet and bleed air out of the system much like bleeding brake lines. It works well since AF isn't lost while the air percolates up the tube, and you can see thru a clear tube to know when the air is gone. I dropped my bleed screw and couldn't find anything to match the thread but the mini valve. A few feet of hose running straight up to the hood works great!
John

[meggabad]

Did you find that in the plumbing section of Lowes, and did the threads match?