New water pump installation - pump not spinning freely (997 pump in a 996)

I'm in the middle of replacing my water pump and I think I've hit a snag. I just installed the new pump but the impeller is getting caught on the block. This is on a 02 996 Targa. I have a slight feeling that this is normal but I haven't been able to been able to find any significant discussion on the subject. The tolerance between the impeller blades and the engine casing is very small. Did porsche use a plastic impeller so it could wear slightly against the engine to minimize any gap? For a bit of background, I decided to replace my water pump as preventative maintenance this winter since I had some of the car aparty anyway (ignition coil replacement, oil fillter tube etc). I ordered a genuine Porsche water pump from ECS tuning and it looks identical to the one I just removed although the part number was now a 997 part. I'm replacing my thermostat with a low-temp version and flushing the coolant while I'm in there. I only screwed in two of the bolts and then tried spinning the pump but it only makes it a few degrees before it stops. There is a chance that I could get it to spin by hand (clockwise) but I wanted to check before trying harder. I can't see for sure what is blocking the impeller from spinning but the gasket is definitely clear. Pulling the pump away from the block by a few mm doesn't help so it must be hitting the side edges of the impeller. I removed the new pump and put the old pump back on. It spins freely (obviously) with no contact to the block. The new pump and new gasket is aligned and there doesn't seem to be any movement in positioning. I assume that this is slightly expected. Is the best solution to mark each blade to find which is hitting and then sand them down slightly until it spins freely? Other options appear to be - return the pump as defective. Or at least ensure that the 997 part is expected to be an exact fit on the 996. - screw in the remaining bolts, torque them appropriately (once I get a 1/4" drive torque wrench) in criss-cross order, and then try again and hope that the problem disappears. This will compress the gasket though so I'd prefer to avoid this unless it is going to help - assume the edges of the block are there to shave the blades down slightly and trust that it will spin when the car starts up Any help for this noob? The two pics are of the new pump installed (2 bolts only) and the old water pump. The old pump has a little wear on the blades and doesn't quite spin a smoothly as the new one, but no play and is otherwise fine. The car has ~90K km on the original pump.

If you are sure the new pump is sitting squarely with all the bolts in and it's still scrapping, I would recommend a refund. I got mine in 11/2012 from Sunset Porsche with no fitment issues whatsoever. The p/n is 996-106-011-56, which is still the latest version per autoatlanta.com I have an '03 C2. What's your pump's part number?

Is it this one http://www.ecstuning.com/Porsche-200...ump/ES2535586/ If so, it's not for our cars. It's for 05+ 997, caymans and boxsters per autoatlanta.com Edit: now saw your p/n in the photo. Definitely send it back to them for a full refund. Also, try Suncoast Porsche, closer to waterloo.

Thanks Ahsai. I obviously noticed the 997 part number when I ordered but I assumed that they were interchangeable since ECS had it listed as the only pump for my 02. But looking now I can see that the 996 part is still listed as current from multiple sites. I thought I had read on the forums that the 997 water pump was interchangeable with the 996. Apparently not. Sigh. I'll call ECS and get them to return it. And I'll measure the impeller against the 996 part to see what the difference is and post back here.

Kevin; Off-topic but is your Targa, a T4S given what I see as a Turbo front grill? Your signature describes it as a plain Targa. If not T4S, is it an OEM front end with a 3rd central radiator that you installed yourself? Good luck with the right 996 pump! Mine blew on me last fall but I was very near and uphill from the house and could coast to my garage. I will never be sure if I got all of the plastic impeller pieces though, so you are doing the right prev. maintenance. Cheers! Martin

Thanks Martin, My car is just a regular Targa (ie C2) but a previous owner (or possibly even Porsche) had installed the C4S front end and ground effects. I have never actually thought to look for the 3rd radiator but I'm 90% sure that it wasn't installed. It has been a few years since I've had to pull my front bumper :-) The car has a few "custom options" in the option list so there is a chance that it was ordered that way from the factory. I think it definitely helps the look.

OP, Part Number is 99610601156 also use 99610634054 which is metal gasket (Victor Reinz)

Just a quick update for anyone reading. Jonathan from ECS actually contacted me based on this post and straightened everything out....even before I had a chance to call or email. They also updated their web site to remove the 996 from the application list of the 997 water pump so the confusion shouldn't happen again. A new 996 pump is on its way with the proper part number. ECS took care of the shipping and rushed the order. So needless to say I'm extremely impressed with the service from ECS Tuning. I will take a few measurements tonight on the impeller and post them here for reference.

That's what I call great customer service!

Quotes source post: 11071959

I am very impressed with ECU as a parts supplier, and haven't had any experience with much else (Shop wise). I think the amount of forums they sponsor are great and am proud they represent the big OH!

Agreed. And not only do they sponsor the forums apparently they read them too. For future reference I measured both water pumps side-by-side to find out why the 997 pump doesn't fit. The only significant difference that I could find is the size of the impeller. The diameter of the 996 impeller measured from the outside edge of the opposite fins was ~64.8mm. The diameter of the 997 impeller measured ~66.9mm. The height of the fins were the same within my ability to measure (within 1/10th of a mm). The casing actually had the same part numbers (996 106 101 and 0070905063) but with a different version (07 vs 09). The diameter of the hole for the impeller was slightly larger on the 997 but only by ~1mm. There are a few other minor differences that are visible from the photo. The overall height of the two pumps was slightly different (by about 2-3mm) as well although I didn't take the time to find out why. I couldn't find any other measurable changes though. My guess is that Porsche revised the water pump casting to be able to fit both the 996 and 997 impeller, and then increased the size of the impeller very slightly for the 997. The diameter only increased by 2mm which seems like a very trivial amount especially since they now have to maintain two separate part inventories. I think it could be possible to file down the 997 impeller to fit into the 996 but clearly the parts aren't interchangeable as shipped. My used 996 pump is on the left (obviously). The new 997 one will be going back to ECS shortly.