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Old 03-13-2017, 08:18 AM   #1
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Water pump longevity ????

Have a 99 Boxster w/ 91K.. Runs perfect.. Read about water pump and stat failure.. So I decided to change them.

Changed the water pump and stat this w/e. The old pump looked perfect, no shaft movement. The composite impeller all intact. How long does a water pump last in these cars ?? I've heard some horror stories about pumps failing and spitting pieces of impeller into the system.

Went with metal impeller pump and a 71C stat. The other question is ?? Will the 71C stat help bring the temp down a few degrees. Ran a 'little" warmer than I liked last summer.. Anybody got experience with the swap to a 71C stat ??
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Old 03-13-2017, 08:48 AM   #2
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Have a 99 Boxster w/ 91K.. Runs perfect.. Read about water pump and stat failure.. So I decided to change them.

Changed the water pump and stat this w/e. The old pump looked perfect, no shaft movement. The composite impeller all intact. How long does a water pump last in these cars ?? I've heard some horror stories about pumps failing and spitting pieces of impeller into the system.

Went with metal impeller pump and a 71C stat. The other question is ?? Will the 71C stat help bring the temp down a few degrees. Ran a 'little" warmer than I liked last summer.. Anybody got experience with the swap to a 71C stat ??
Water pumps usually needs to be changed when timing belts get changed. Since our cars are chain driven it's a stand alone process at around 60000miles or 100000km. Water pumps tend to fail un-dramatically usually. They leak coolant thru a hole once the bearings gain some play. Considering the location of the engine, it would be hard to pick up. Now the plastic pumps might fail earlier, but that would be due to lack of coolant maintenance and just poor design of the composite.
Source:
"https://www.renntech.org/forums/topic/29955-need-help-identifying-coolant-leak-source-under-986/"

About the 71C thermostat. What tells you that you need to bring down the temperature? A proper working system is all you need. Someone might have tested the full opening temperature of a 80C vs 70C, at WOT (Wide open trottle) your car will be running at around 90-100C and flow will be the only thing limiting your cooling. The only thing you will be doing with the 71C is that on cold days, your oil will be 10C lower then normal because of the oil to water cooler. Which is bad since oil should be running at 100C+ to allow the removal of all water condensation in the engine.

Source: "https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=632716"

Good luck!
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Old 03-13-2017, 10:10 AM   #3
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One point. I've repeatedly had it drilled into my head, by smarter people than I, is to avoid water pumps with metal impellers like the plague. When that pump fails (when, not if), the wobbling metal impeller will be chewing up part of your block. That will result in an increased gap between the impeller and block, leading to poor water flow. And it can't be fixed short of a new block. I'd much rather sacrifice an impeller than an engine block.
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Old 03-13-2017, 10:11 AM   #4
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On another forum Marc reports 172k on his first with 130K+ on his second pump.

Some discussion on if a metal impeller is a good idea. If the bearing goes and it starts scraping the cavity it can create real serious problems. The plastic impeller is softer than the cavity. And once the cavity is made larger, any pump is less effective.

A thermostat opens and allows flow when the temps are reached. After that, the cooling is limited by the capacity and cleanliness of the radiators and the working or not of the fans. No big need for a low temp thermostat in most situations. Because once it gets hot, the flow is there no matter which thermostat you use.
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Old 03-13-2017, 10:37 AM   #5
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Old 03-13-2017, 01:56 PM   #6
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Mine failed at around 58K. The impellers looked great and the pulley spun freely. It just started leaking heavily after a drive one day. No visible damage.
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Old 03-13-2017, 02:19 PM   #7
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I've replaced my water pump twice in 100k miles
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Old 03-13-2017, 02:28 PM   #8
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I've replaced my water pump twice in 100k miles
You've either been unlucky or very cautious.

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Old 03-13-2017, 02:49 PM   #9
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Metal impellers are a no-no. Why take the chance?
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Old 03-13-2017, 04:49 PM   #10
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Thank you for the information on the water pump, and the thermostat..
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Old 03-13-2017, 05:11 PM   #11
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Replacement schedule...

...for water pumps is TIME, not mileage based.

One of the failure modes is the plastic blades breaking down and bits of them floating around and blocking the coolant passages. That is bad.

But, like the others have posted, you do NOT want metal blades for the reasons they cited.

So, you must just own the idea that you must R&R the pump with a fresh OEM unit every FOUR years.

Do that, and you will be fine.


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Old 03-14-2017, 03:16 AM   #12
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...for water pumps is TIME, not mileage based.

One of the failure modes is the plastic blades breaking down and bits of them floating around and blocking the coolant passages. That is bad.

But, like the others have posted, you do NOT want metal blades for the reasons they cited.

So, you must just own the idea that you must R&R the pump with a fresh OEM unit every FOUR years.

Do that, and you will be fine.


???? Every 4 years regardless of mileage? Where do you get this from? That makes no sense. Yes, age plays a factor, but mileage = the useage and that's what wears it out. Hence why most change it when they would do the timing belt ( or in our case, around that 100 k mark). 4 years....man....
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Old 03-14-2017, 04:13 AM   #13
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You've either been unlucky or very cautious.

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I guess it's unlucky, because in both cases they were leaking.
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Old 03-14-2017, 04:23 AM   #14
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???? Every 4 years regardless of mileage? Where do you get this from? That makes no sense. Yes, age plays a factor, but mileage = the useage and that's what wears it out. Hence why most change it when they would do the timing belt ( or in our case, around that 100 k mark). 4 years....man....
Here's one place where Jake R. says to change them every 3 years:
Water pump: plastic impeller or metal? - Page 2 - Rennlist Discussion Forums
Lots of discussion on our forum over the last couple years too.
Personally, I plan to change mine about every 3 years. In doing so, I feel fine about using a metal impeller pump and flushing out my Prestone coolant . Still, you can get Pierburg at a good price if you shop around.
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Old 03-14-2017, 04:43 AM   #15
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...and here are two OEM water pumps that I've pulled from cars shortly after purchasing them:



A 'new-to-me' Boxster will get a new pump and flush unless it has a recently documented replacement.
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Old 03-14-2017, 05:58 AM   #16
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I bought my car as a summer, tinker with, do it myself, sports car. So I will replace my water pump every few years with a metal impeller version. Not that big a job. That way it gets me under the hood to look around and see what else needs doing. This year it is water pump, alternator and belt so far.
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Old 03-14-2017, 06:03 AM   #17
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... and a 71C stat. The other question is ?? Will the 71C stat help bring the temp down a few degrees. Ran a 'little" warmer than I liked last summer.. Anybody got experience with the swap to a 71C stat ??
I don't think we discussed the 71C/160F Thermostat enough. Here's the reading assignment:
http://986forum.com/forums/general-discussions/37198-engine-thermostat-low-temperature-begins-opening-160-deg-f.html
http://986forum.com/forums/general-discussions/33593-why-i-installed-low-temp-thermostat.html
http://986forum.com/forums/general-discussions/21309-low-temp-thermostats.html
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Old 03-14-2017, 06:53 AM   #18
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After reading this I am definitely going to change out my pump this spring (66k). This is why I love all the helpful people and experience on this board. Where do you guys order the T stat from?
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Old 03-14-2017, 08:09 AM   #19
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Unless you track your car often I would suggest not running the lower temp thermostat. Someone starting by "it is actually a fact" and doesn't provide sources isn't credible. Will it break your car? No. Will it give you more power? Maybe for a short period. Most of you change your oil way too often already and cover the consequence of running a lower temp thermostat. If you want to start throwing your money away go for it.

About the water pump, I would love to see pictures of the "chewed up area". They are centrifugal pumps and if you catch the mild leak, you shouldn't build enough play to have contact. Even if there is contact, that gap will provide more flow at higher RPMS since you will be making the path wider.
Source:"http://www.mcnallyinstitute.com/12-html/12-06.html" It talks about trimming the impaller to make more gap, but if the cavity gets bigger it should have the same effect.
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Old 03-14-2017, 08:28 AM   #20
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Quote:
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Unless you track your car often I would suggest not running the lower temp thermostat. Someone starting by "it is actually a fact" and doesn't provide sources isn't credible. Will it break your car? No. Will it give you more power? Maybe for a short period. Most of you change your oil way too often already and cover the consequence of running a lower temp thermostat. If you want to start throwing your money away go for it.

About the water pump, I would love to see pictures of the "chewed up area". They are centrifugal pumps and if you catch the mild leak, you shouldn't build enough play to have contact. Even if there is contact, that gap will provide more flow at higher RPMS since you will be making the path wider.
Source:"http://www.mcnallyinstitute.com/12-html/12-06.html" It talks about trimming the impaller to make more gap, but if the cavity gets bigger it should have the same effect.
Can't agree to eithier point.

We have run 160F stats on fully insrumented cars and consistenly found both lower coolant and more importantly oil temperatures when operating at steady state (cruise speeds). Coolant temps typically drop from around 205-210 to the mid to high 170F range. Oil temps drop 20-25F. Used oil analysis on cars befor and after adding the low temp stat showed the oil was in better condition after equivlant usage.

We have had multiple cars in the shop that had metal impeller pump failures that resulted in significant damage to the engine cases behind the pump. Several of these cars showed coolant circulation issues after being fitted because the new pump lost efficency due to the increased gap behind the impeller. Trimming impeller blades is a method to slow pump circulation rates, which is an old racers trick to improve high engine RPM cooling as usually the pump is moving coolant too much coolant under those conditions. But like everything else, there is a "too much" limit in doing this, when the reduced flow leads to over heating, particularly at lower engine RPM levels.

There are reasons the factory used compostie impeller pumps on these engines, and why they equip all of their high performance engines (turbos, etc.) with 160F stats from the factory.
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