perrys4

I figured it was the impeller but wanted to get that confirmed. Thought that it also may have been caused by something hard running through the cooling system (plastic piece, ect.) and getting tangled in the pump. Just want to learn as much as I can here.

BC

Its been sveral months this time. I hav had 928s working for several months at a time since 2005.

GregBBRD

Water pumps originally were equiped with metal impellers. When the bearing went bad, or the impeller moved, the blocks got pretty torn up. Never had any problems with one overheating when replaced, just looks bad. At some point in time, Porsche changed the impellers to the infamous plastic impellers....not sure exactly when, but I think it was about '90. They changed them so that the blocks would not get damaged. The problem with the plastic impellers is that they can come loose on the metal piece that they are cast around and not move water very well. Interesting thing to trace. The engines will stay cool at idle, but overheat as the rpm's go up.....when the impellers first come loose. Rebuilt pumps come either way, since they are usually reusing the impellers. We try to use metal impellers on anything that is going to the track or is used for high rpm use. We use either one in street cars. Most of these cars are now in the hands of people that care and notice things....like a severe grinding noise from a bad water pump bearing.....so the metal impeller is not as big a liablity as it originally was.

greg brown

Vilhuer

I believe my GTS had original pump before engine teardown and it has metal impeller.

BC

The pump that I took off is a metal impeller, and I will reuse it, as it has about 4k on it, from what H and Bill said.

Jim bailey - 928 International

This really points out one of the downsides of taking things apart . What was running working just fine and would continue to do so may not be all that pretty. The "while you are in there" lists can really get lengthy.

jon928se

Oh Jim you're no fun at all.

If it ain't broke take it apart until it is.

BC

This is an improvement Jim, you don't see it. I have a daily driver and I am enjoying most of this. This will be the last car though for a while. Too much grease and dirt.

With the scratches on the bores, I may just look for a tolerance 0 or 1 block. I'll have to see what Motorwerks says.