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 ??

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!

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.

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.

Penny wise and pound foolish to use a metal blade WP

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.

I've replaced my water pump twice in 100k miles

You've either been unlucky or very cautious.

Sent from my SM-G928F using Tapatalk

Metal impellers are a no-no. Why take the chance?

Thank you for the information on the water pump, and the thermostat..

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.


:cheers:

???? 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....

I guess it's unlucky, because in both cases they were leaking.

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 :eek: and flushing out my Prestone coolant :eek:. Still, you can get Pierburg at a good price if you shop around.

...and here are two OEM water pumps that I've pulled from cars shortly after purchasing them:
http://986forum.com/forums/uploads02...1469369944.jpg
http://986forum.com/forums/uploads02...1489495295.jpg

A 'new-to-me' Boxster will get a new pump and flush unless it has a recently documented replacement.

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.

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

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?

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.

I like MarcW's water pump change schedule! I think he's still on his original clutch at 300K miles too. Oh, and my 2nd water pump is still holding up after 8 years (original one lasted 8 years), so I hope the AGE theory doesn't hold water.

That and what this other guy said that I was about to quote:
(From 2012)

:D

There are a few on this forum that consistently know WTF they are talking about and JFP is one of them

JP, you are just throwing information that is not possible to measure easily and if you did, should have graphs and data showing it.

About the thermostat. You are measuring the temperature after the thermostat, not at the radiator. All 986s(without center rad) has the same thermal capacity. The only difference is that the proportion of the heat is located in the engine or in the radiator given the same amount of usage and type of usage. The delta temperature(difference between two values) will be different I agree, but it will not affect daily function or be worth it. All you will get is a car that is terrible to use in the morning when its 40-60F outside with much less cabin heat and increase emissions. Considering even california weather that is still half the time used as a commuter.

About the impeller damage. I would love to see pictures. Also considering the person who let a weeping pump long enough for the water pump to fail axially, they wouldn't see the difference in coolant performance anyway. Proper usage you wouldn't see major failures of the pump.

I am just trying show that people should look at a choice in the big scheme of things rather then facing specific problems. Lower Thermostat, under driven pulley, oil cooler, 3000 miles oil change on synthetic , great way to make money on people with more money then time to educate themselves on their car. Listening to "experts".

Again, I disagree. And I apologize that the shop does not take the time to prepare pretty Power Point presentations for you, but that is not what we are about.

The thermostat functions as a throttling device, restricting the volume of coolant returning from the radiators to the engine. As such, a lower temperature stat actually opens sooner (read at a lower temp) than the factory stat, so operating a vehicle with a 160F stat will actually get heat sooner than with an OEM stat. This is a common observation customers give us after changing over, and as we live in an area that often sees weeks of zero or sub zero temperatures, customers that use their cars as daily drivers would be screaming if there was a heat or warmup time issue. Yet in all the years we have been installing these stats, we have not had one complaint, only comments that is nice to get more heat sooner in the winter because the stat is opening sooner and allowing more warm water to circulate.

Metal impeller pumps do not have to completely fail in order to chew up the engine cases. There is only a few thousandth's of clearance between the impeller and the cases, and when these pumps start to wear and the impeller shaft starts to wobble, and they all do, the machining starts. We have had cars come in with complaints of seeping pumps, only to dump the coolant and find it full of finely ground aluminum, requiring us to flush the system to get all the metal out. And after installing a new pump and fresh coolant, the cars returned with complaints of running hotter than normal, particularly in warmer weather. A couple of these customers got annoyed enough about this issue to take the cars back to a dealer, who pulled the water pump, looked at the damage, and promptly told the owners that they needed a replacement engine as the impeller damage could not be repaired. They also confirmed that this is something they see regularly with metal impeller pumps, and why Porsche does not use them.

As for whether or not people choose believe, or even listen to what I have to say, that is entirely up to them. And quite plainly, I do not care if they do or do not choose to listen to us. Those that know me will tell you that I have never posted the name or location of my business online, or on any of the forums I either moderate on or participate in. We don't need any more business than we already have, we are doing just fine. We simply try to inform interested parties in what we have observed or experienced over some thirty years of building, racing, and repairing Porsches.

I though mine failed at about 125K...I had a very slight coolant loss. During replacement, I realized that one of the mounting bolts (lower passenger side) was very loose. I went ahead with the replacement (along with thermostat) but my original pump looked fine as far as no play and no impeller wear.

Oh well.

+986, 996, 987, 997, 981, 991, 911, etc

You don't want to take his advise, don't.
No skin off his nose or anyone else

Before low temp thermo, hwy cruising was right around 194 degrees, summer time.
With low temp, my summer temps run around 176 degrees. In the winter it runs 172 degrees. This is using the Torque app for water temp.
Now in stop and go the temp will move up in the 212-215 and the fans come on same as reg thermo. But cruising 50+ mph the temp definitely runs cooler.
Cooler is better

I appreciate that you help the community. I won't argue that its the only reason why I keep participating. My field of work require thorough study of every situation and we can't forget the big picture. I am just trying to say that the solution isn't always clear cut. You might solve 1 issue and cause two problems. Just like IMS issues is to Porsche cutting cost on engine head castings .

As a friendly reminder, re-read yourself on the heater core part. Heaters(cabin radiator) and engine are on a closed loop system. No thermostat in between. In the morning, you will feel heat at around 100F on the cluster.

The result is the same(negligible error considering its two different test moments)... 176Fis 6Fto 170F and 194F is 8F to 186F. that 6-8F is the limitation of flow.

At max heat capacity(radiator at 212F), both thermostats should be open at 100%. ANY difference in flow here would mean one is actually better then the other. Under that situation you could say one thermostat is better then the other. Any other test in meaning less for a daily driver. Tracked Cars are a different story where you can tune the fuel and timing map to take advantage to the lower intake temperatures.

The heater uses a small bypass from the engine, but when the thermostat opens, more warm water is in motion within the cooling system and the engine, heat comes up in greater amounts within the cabin; so the thermostat does affect how much and how soon you sense heat coming from the car.

And, regardless of what you do for a living, it is never a good idea to look down your nose at anyone.......................

Just an observation.

I've learned a ton from JFP and he has never steered me wrong. His experience with multiple Porsches over a long period of time has allowed him to see many, many more failure modes than any one of us will observe. The large sample size of cars he has been exposed too with & without low temp stats and with & without metal impeller pumps tells me his practical experience in this area carries more weight than the theoretical viewpoints.

One very real world piece of knowledge that JFP shared was to always use Porsche Brand MT fluid in the 6 speed. My thoughts were 'hell, gear oil is gear oil. It's all the same". Well I ignored JFP's advise, went with XXXXX brand and the shifting could only be described as s#itty. I drained it, put in the 'unicorn tears' oil from Porsche and it is 100% superb.

Like Jake Raby, JFP has seen it all. We would all do well to heed his advise when it is freely given.

Totally Agree with this
 

I too have learned a great deal from JFP, couldnt agree more

Metal vs Composite impeller...
 

Posted a few days ago about installing a pump w/ a metal impeller. Live and learn, I guess.. Do more investigating before purchasing parts for these cars, especially something engine related.. Asking questions is never a bad idea.. Plenty of people way smarted than me out there.

Anyway, pulled the "brand new metal impeller pump" and installed a Pierburg w/ a composite impeller. Works great.. Getting to be an expert on pulling and installing these pumps.. Thanks again for the insight, feel better about things.. Pumps are cheap compared to engines..

As I post earlier I also installed a 71C (160F) stat when I did the first pump.. I agree with JFP in Pa after running the car with the new 71C stat vs. the old 83C stat.. The temp needle now sits just just a hair behind the 180 degree mark after running and letting sit for 25 minutes idling and some minor revving.. It never moved past that mark.. With the old stat the needle sat about 1/4" past the 180 degree mark and would creep up on warmer days.. As I said earlier the old factory pump looked perfect at 91K, so I'm sure the circulation was always there.. I never liked how warm it ran before.

This improvement, I feel, is all T-stat.. More driving to do, but at this point I would recommend the 71C stat.. Inexpensive and really pretty easy to do..

Thanks to all for info and sharing experiences.. Knowledge is power..

+1
JFP has provided much advice to this forum and others. In addition he has answered PM's from me when I first purchased my 986. I respect his knowledge and his generosity. :cheers:

Probably in a thread but I haven't seen it and seems appropriate here. When replacing the water pump, are you replacing the hoses and flushing all coolant? I'm planning to replace pump and tstat in the next couple of months. See a lot of discussion about that but very little about hoses and actually flushing coolant.

Thanks - Bryan

FWIW, I did not observe any signs of needing to replace any hoses or clamps. Neither did I replace the coolant because it was recent.
But do carefully account for all the impeller blades
What is of great value is to remove debris from between the radiators and condensers.

Yes....
 

....Every four years.

Mileage is NOT the killer. It's the coolant chemically breaking down the impeller plastic over TIME.

I don't understand why this is such a big deal for people to understand.

Just install the lower temp thermostat and slap in a new OEM water pump every four years.

No. Big. Deal.

It's not a Corolla.

EVERY high performance car has "issues" like these. It's the cost of enjoying a bad ass car. Go talk to the BMW "M" crowd or the MB AMG crowd, or talk to the guys whose Corvettes have grenaded on them.

Just budget a new water pump and AOS every four years.

Simple.

you pretty much have to drain out the coolant when changing the WP

are you reusing the drained out coolant?
IMHO that is a penny wise and a pound foolise