Water pump recommendations

Some projects on my To-Do list for my ‘08 Boxster include serpentine belt, tensioner pulley, idler pulleys, plugs and coil packs and assessing my water pump for replacement. Figure replacing it before it fails instead of waiting for it to fail is the prudent approach. Researching parts for the water pump comes down to ‘composite‘ impeller versus ‘brass’ impeller. Anyone who has been down this road please share your thoughts/history. Thanks.

The choice is - metal vs plastic. The plus for metal - some early plastic impeller water pumps had issues with the impellers cracking and falling apart, scattering debris throughout the cooling and heater systems, requiring fairly massive disassembly to correct. That isn't an issue any longer. The cracking ones were first used by BMW about 20 years ago. They had so many crack they went back to metal for a while, then finally came back to a long-lasting and stable plastic impeller. Porsche from the factory uses plastic impellers. There is a disadvantage to metal impellers - if a water pump fails due to bearings and the owner of the car is deaf and doesn't realize this - the impeller can move enough to score up the metal surface behind it, making any replacement pump less effective. This was an issue on early (pre-'09) Boxster engines - where if it was bad enough, and the owner didn't know someone who could weld back material and then grind it back to shape (or use JB Weld to achieve the same thing) - it was new engine time. Major bummer when it happens. This issue (and MANY others) was fixed in the 2009+ engines - not only did Porsche come up with a water pump with a very low failure rate, but they redesigned the engine so the water pump mounts to a replaceable metal plate that is bolted to the engine. If it got scored up (never heard of any that did) you can order a new plate (it has a PN) and just replace it and you're off to the races again at minimal cost. BTW they still used plastic impellers on the water pumps.

When I was researching the 981 , I, too, was concerned about waterpump replacement. I talked to a Porsche service tech who had been in the business for over 10 years and said he'd never seen a pump go, even on cars with over 100k on them. YMMV. When I change the belt and pulleys I'll check for play on the pump, but if it is firm, I'll wait and watch.

Water pumps do go bad….if you track your car, consider the pump a wear part and replace every 4 years. Ask me how I know. An underdrive pulley is also a good investment for all the driven pumps in the car….

I've had 7 Porsches; one for 8+ years (2000 S 986 ) and hundreds of track days and never replaced anything to do with a water pump. 944 986 987 987.2 981 Macan 718 Only things ever replaced was the lifetime anti-freeze (the 986S) as I didn't believe it was lifetime. And replaced the pulley and belt to reduce it's speed/hp use.

Update: I started this discussion as I was going to be proactive and replace my serpentine belt, and as I was beginning to hear a little more engine sound than I thought normal, figured I would replace the idler pulleys and the tensioner pulley. I had then inquired about thoughts on which water pump to use should I need one. Metal impeller versus composite impeller. Turns out that when I pulled the belt today to check on the status of everything, all three of the pulleys seem fine. They spin freely and quietly, but when I jiggled the water pump pulley there was a couple of millimeters of play fore and aft. Question is, (although I pretty much know the answer isn’t going to be what I want to hear), does this indicate replacement? I’m figuring there should be zero movement fore and aft. Now that I’m going to be shopping water pumps, what is the consensus: metal or composite? And should I replace the thermostat while I’m in there? And since I’m going that far, should I take the next step and replace the coolant hoses? I enjoy doing these projects myself, but was wondering if it’s worth taking to an Indy shop since I would also need to purchase a coolant fill kit to do,it the right way. Any guess on what an indy shop would charge for this? Trying to determine my next step, and always appreciate the collective brain power of our Porsche community.

I believe you should replace it while you're there. Composite/OEM gets my vote. Don't try to outguess the engineers who designed it. Thermostat, sure... hoses, maybe. I strongly recommend an air-lift type kit. I know Don has had great luck with the Harbor Freight version of this device - it makes refilling MUCH easier. I had my indy do a flush/fill and he took many hours trying to get all the bubbles out without it. My indy charged $1704 back in Nov 2021 to do the water pump and flush/fill. He also recommended the OEM composite pump, and I was fine with that, of course. EDIT: They did the thermostat at the same time as well. I think they inspected the hoses and felt they were fine, which is why they didn't do those...

Thanks for the feedback, I’ve been going back and forth over which route to take. Definitely going to do the t-stat at that point. I typically would do this job, but in speaking with my indy, I might have him do it because I would need to purchase a vacuum lift refill kit which I most likely wouldn’t need again, and it seems like a lot of contortion to complete. If only I had a lift…..

The vacuum lift kit from HF is cheap. Heck, you could buy it for your indy if he doesn't have it (sounds like it does) - that's what Don did. If I do another coolant change on my car, I will probably buy it and give it to my indy, as Don did... it's worth it for everyone.

That’s a good thought. I know a coolant refill calls for the vacuum refill kit, but I know from past vehicles, (non- Porsche ) that when you crack the coolant expansion tank after a short cool down period, you get a whoosh of air pressure releasing. Would that equate to refilling the coolant system, warming the car up, bleeding off the pressure and topping of until all the air is purged? Or is this system designed in such a way that you absolutely need the vacuum refill kit? It goes against my DIY history to take my car for a repair I can do myself, but it seems like a real PITA job because you have to work under the car, then inside the car, then under again, rinse, repeat. And my indy doesn’t charge me a markup on parts and goes easy on the labor costs so it just seems like having him do it will cost me less headache and swearing.

One point about the Harbor Freight air-lift system. When I was checking out - the guy at checkout made a real point to make sure that I knew it could be returned for ANY reason within 90 days of purchase (I assume this is still correct) - almost like he was encouraging me to use it and then return it... but that couldn't be right? I'm not quite that "thrifty" and I was saving money by buying it and giving it away (1 airlift tool @$75 vs 2-3 mechanic's hours bleeding at $160/hour - do the math.. The bleed took less than 30 minutes using the tool..) Since I figured I'd likely never need it again (and if I did I'd know where it was..) I gave it to my mechanic (who has said it's great on British cars..) BTW - take a look sometime for an illustration showing the entire cooling system on a mid-engine performance car - that will answer that question. The answer is "yes" you need it.

As far as the service tech in business for over 10 years and never saw a water pump go, well I guess he’s been lucky because my water pump has ‘gone’ and needs replacing. My indy told me my water pump, thermostat and serpentine belt replacement will be about $800-1000.