I am changing an impeller on a 07 GTI 4 tec. It is a simpl job but is there a torque spec on putting the new one on or just get it "tight". Thanks!
The torque for your impeller may be a bit different, depending on who you ask. I've read that torque for the aluminum pump casings are set around 65 lb's and for plastic, 35 lb. But, if you go by the procedures that are provided by the Impros, if you buy one of their impellers, they say to tighten to 90 lbs.
Me, when I change out a set of bearings or remove the impeller for any reason, I make sure the shaft and threads are clean, then apply loctite red and simply tighten. Some have used the blue, which holds the shaft threads tight into the impeller, but can be easily removed. I use red because to make it release, you have to apply a small amout of heat (up to 300*F if I remember right), and I keep a torch in my shop.
I've never had an impeller back off on me, so figure the torque is to ensure a uniformed procedure for a shop manual. But, the most important thing (for oil based impellers) is to make sure your thrust bearing ring is set in the casing and not pinched by the shaft as you tighten it. If you do this, you will know because the shaft may not turn, or if it does, will be really stiff.