Water Pump Impeller Differences

[Guest shadetree77]

A lot of you might have been following along on my recent cooling issues. I posted at some point about the impeller on my re-built water pump from Bob's being completely different than the impeller on my original unit. I thought these differences might be causing some flow issues in my cooling system. Somewhere along the way, one of you guys asked me if I had any pictures of the two pumps side by side. I didn't at the time, but after having to take the "new" one off to send it back due to bearing failure, I took those pictures and here they are. "New" unit is black and on the left, original is rusty and on the right. At first, you don't really see a big difference. But look closely and you'll see that the "fingers" on the new unit are shorter and thicker which cause a difference in the spaces between the "fingers". Also, the flat part where it mounts to the shaft is different too with the old unit having some kind of indented circular place in the middle. Whether or not these differences cause flow issues is still unknown, but I do know my old pump seemed to pump harder and cause more churning in the top of the radiator.

[old-tank]

There is a visual difference, but it is unknown if there would be a difference in performance. When the water pumps are rebuilt the old impeller is used, so just get that original rebuilt. (Yeah, I know more $$$ and delay...)

Willie

[avgwarhawk]

I don't know about the sizes of the fins and such but the new pump looks wiped out! Your old pump looks in better shape!

[JohnD1956]

If you still have the new unit, try to get a measurement of how deep the impeller blades are from the gasket surface. There has been talk that rebuilt units sometimes have had impellers ground down to remove rust and pitting and the result is the impeller winds up too far away from the housing surface, thus creating a loss of pumping ability.

[Guest shadetree77]

Willie, I did keep my original pump despite losing the $65 core charge. My incessant need to keep this baby original kicked in when it was time to send it back and I just couldn't let it go. One of these days I'll get it re-built. Until then, Bob's is supposed to send me a replacement for that defective unit. I agree Chris, my original is in much better shape. If you'll remember, I had a gripe about the backing plate that came on that re-built one too. Overall, it was a very shoddy rebuild. John, unfortunately that "new" pump is already in a box on its way to California right now. That may very well have been the case though. That impeller looked to be in pretty rough shape and if it was ground down that would explain the lack of a part number like the original has.

[JohnD1956]

I have to wonder if the CLR treatment took out that bearing?

[Grandpa]

If you have concerns about the new pump, rebuild your original pump. A local water rebuilder charged me $89 to rebuild my Buick pump. Send me an AACA PM if interested.

Grandpa

[Guest shadetree77]

I have to wonder if the CLR treatment took out that bearing?

I thought about that too John but I don't see how it could have. CLR claims to be environmentally safe and it even says that it won't kill grass or plants. I don't see how it could eat into a bearing if it won't even kill grass. That and there have been others that used CLR in their cooling system with no ill effects. When it comes right down to it though, I can't say for sure. I'm no scientist, just a shadetree mechanic. All I know is that the pump they sent me was pretty rough looking to begin with so it wouldn't surprise me if the bearing in it was defective. I guess saying "use at your own risk" would be appropriate.

Grandpa, Thanks for the suggestion. If I do end up getting the old one rebuilt I'll contact you.

[buick man]

Don't know just how the straight eights water pumps shape up into or mate with the block, but I do know on the 57/58 that the impeller has to be within tight specs of the timing chain covers inside surface in order for the draw to be meaningful and accurate. Corrosion on the nailhead V8 timing chain inside cover can cause a larger gap and thus hampered flow characteristics. This corrosion often occurs during long term non use and aging acidic coolant as coolant becomes more acidic as it ages. This is especially true if the water pump is aluminum and the block is metal. Dissimilar metals and electrolysis.

I am currently looking for a 5 bladed impeller for my 57 as I want to replace the 3 blade one currently on it. The 5 blade was used on the 58 models with AC. If anyone knows a good source let us know.