UPDATE:Thoughts on preventative water pump replacement @ 79K MY'03

I just installed the IMS Guardian and then discovered that the expansion tank was leaking. Replaced the tank. Now I'm wondering if I should replace the water pump as a preventative measure. It's not leaking or making bearing noise. I've been reading old threads indicating that the plastic water pump impeller degrades with time and fragments can plug capillary coolant passages in the heads leading to catastrophic engine damage(as per Jake). My car is an '03 and apparently this problem happens mostly in pre ' 02's(as per Jake) . What about post '02's? Apparently the head design changed in '02 but I'm wondering if later model 996's are still vulnerable. My car is at 79K. Should I just wait until replacement is indicated? What about after market pumps with metal impellers that are less costly that OEM. Are those a pumps a good idea? Input is appreciated. UPDATE: Today I replaced my water pump and the old pump's impeller is chipped. I hope I caught it in time before catastrophe , but I am worried where that tiny chip is lodged. Also, changed the coils Four were cracked.

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I was told once the 997S pump is a bolt on replacement with larger fins which should provide better cooling....

I would wait until it started to weep or leak. I think weeping or leaking will occur before the impeller breaks apart. Impeller breaks after the bearing fails, causing the impeller to bounce inside the housing. It may be better to have small plastic parts in the system than have the metal blades scratch the engine housing.

By the time it makes noise or leaks it may have already shed plastic impeller debris that can end up in the cylinder heads.. While the majority of the failures that we see with cracked heads come from the 2000-01 engines we have seen this happen to engines as late a 2006. No matter mileage we change water pumps every 3 years, whether or not the engine is running the plastic impeller blades are exposed to coolant. The metal impeller blades may not fail, BUT if you have a pump bearing failure the impeller "machines" the aluminum housing away and destroys the engine. Water pumps are cheap and easy to replace.

I agree with Jake and I know people who have changed water pumps before they go bad.... I call them smart - James for one

My 996 3.4l had a water pump impeller failure, the little plastic impeller pieces clogged a passage in the 1-3 cylinder head, overheated and cracked the head. Change the water pump! And I for sure am going to a metal impeller.

what are the reference for metal impeller ? is it a porsche oem part ? There is a good video on youtube showing how to change the pump. I might try it myself, but I am still scared of the vaccum system porsche recommend to refill the coolant system. Apparently the 'burping valve' on top of the coolant tank might not be able to really remove all air pocket from the system. Forum post suggest it could create air pocket/hot spots and also create problems. I wonder how much the dealer will charge me for a coolant flush.

Change the pump when you change your serp. belt.

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The dealer will charge you gobs. Dealing with anti freeze sucks, it is sooooo caustic. I've read from several sources the latest Porsche OEM water pump has a metal or "metal like" impeller. If you have a 5 gallon or larger compressor, an equivalent vacuum refill system such as the one from uview 55000 is one of the best tools I own. It really isn't that hard to refill. Getting all the old coolant out on the other hand... sucks! Yes I've heard of the air pockets too, which is why I chose to fork out the $100 for a uview 55000.

I don't own a compressor but considering that the dealer will charge me $500 for the job, that might take care of buying all the tools needed I have read also that flushing the system takes a lot of work opening a bunch of different purge hose and screws. That's why I am still hesitant.

Can someone who has done a DIY water pump replacement chime in? I thought it was supposed to be a pretty easy procedure?

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If you Go to youtube and type in 996 Porsche water pump replacement...there is a great video(mentioned) so you can decide if that's a job you want to tackle. GL

Thanks for all the input! I went ahead and ordered the water pump at Sunset Porsche and was told that Porsche now recommends the 997 pump for the 996. It costs less too. How cool is that?

Would you share the part #, and is that w/ plastic impellers or metal? Thanks

997 water pump# 99710601102. I don't know if it's the older plastic impeller or the newer " metal like" plastic impeller but assume it's the latter. I didn't think the OEM pumps have metal impellers. Beck-Arney pumps have metal impellers and are about $100 at Rock Auto. I took Jake's advice and avoided that one.

I had my pump replaced prior to failure at about 100K miles with an OEM pump. Based on what I've read here, I won't wait that long for the next one!

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Thanks dennis hiip.

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But what is this about using a vacuum system?

I replaced my wp on my 03 at 40000 miles. Its age, not necessarily mileage that degrades the pump. It was a little challeging but not that bad. Getting the air out of the system wasn't that bad.

I have one very important question. Have you been running Euro Coolant the whole time? If you have not, I would with out a doubt do the pump before the plastic impeller fails. If you have been running proper coolant, I would say its a crap shoot. Mine went 105K before it leaked. But also jake has a very good points too.

Shark - what do you mean by "euro" coolant? Is there a special type not used in the U.S. that means this is less of a worry to us Europeans? thanks Mike

He means OAT antifreeze used by many European cars, and also widely available in the USA or worldwide. http://www.pedrosgarage.com/Site_5/C...ntifreeze.html http://en.wikipedia.org/wiki/Antifreeze "Traditionally, there were two major corrosion inhibitors used in vehicles: silicates and phosphates. American made vehicles traditionally used both silicates and phosphates.[14] European makes contain phosphates and other inhibitors, but no silicates.[14] Japanese makes traditionally use phosphates and other inhibitors, but no silicates. [14]"

There is evidence that water pump blades can brake off and clog cooling passages in the heads. Like the IMS crap, it's not clearly predictable. But if it does, the consequences are significant--far beyond the price of a replacement pump. Once impeller fragments are wedged into cooling passages, you may never be sure that you got them all out. The pump isn't expensive. Even paying a shop isn't crazy expensive to do the replacement. My '03 is getting some years on it, especially when you consider plastic parts. It was a fairly easy decision to have it done. Even easier if you to do it yourself and can effectively purge the cooling system. (I could do more work myself but just don't have the desire. I work on my airplane & its engine, but take the Porsche to the shop.) Like the IMS that came off my car for replacement, the "old" water pump looked fine--which is Exactly what I wanted.

Try opening up the thermostat housing and removing the 'stat - the chip may be lodged in there. Failing that, a reverse flush may be required.....its a bit of a decision on what to do if you can't find it!

If you have a broken piece of impeller one day the problem will find you... It'll start with a flashing coolant level indicator... You will add coolant and in a few miles you will be treated to a 15,000 dollar milkshake in the coolant reservoir... Two just came in last week on the same truck- both DOA. The drivers killed both of them by not STOPPING immediately and calling the tow truck.. One guy said "I only drove it 100 miles like that." Really? WOW.

Next invention: plastic particle detector.

So....what should I do? I'll remove the thermostat and hope I find the tiny piece of plastic. I'll reverse flush as Stephen Tinker suggests if it's not found in the thermostat housing. If not found, then what? This really sucks! Anything else I can do? Being a 2003, just maybe it's less likely to cause a problem.

Ok here it is again. I just picked up my cylinder heads from Costa Mesa R&D in Newport Beach, CA. The repair was made on the cracked cylinder head and both heads received valve jobs and seals. One of the factors was the plastic water pump impeller piece in the cylinder head passage. Now, John, the owner, has been in the business of engines, all types, and his main business is VW, Porsche and exotic new and old engines. He absolutely does not recommend a plastic impeller water pump. Why risk it, and Jake, you just proved it with what you just said about 2 coming in this week. The bearing very rarely comes apart, it just makes noise first and then leaks, just change the damm thing! I am sticking to a metal impeller, and I have good advice on it, but no plastic Jake!

Dennis, removing the 'stat while the cooling system is empty is really easy, shouldn't take you an hour of your time. Backflushing is not too difficult with the stat and pump out - just make sure you flush into a bucket to see if that damn piece comes out. I'm sure I've seen a "how to" description on backflushing, the search function should catch it. After that, maybe someone on here can suggest a good local shop to professionally flush out the system. I guess none of us want to look like scare mongers, but the result of this piece impeller getting stuck in your cylinder head could cause you a lot of financial pain, something no one on this board would like to see happen.

The metal impeller can take out an entire engine... The other mode of water pump failure is bearing failure... When that occurs the very tight clearance between the impeller and impeller is diminished ensuring the steel impeller contacts the aluminum crankcase. When this happens the case becomes "machined" and the result is a compromised engine. We do not use the metal impellers, we simply change water pumps every 3 years, because I have never seen this occur at less service time than that. I have had a composite impeller under development for quite some time but it needs a lot more test time before its ready for the market. Intermixed conditions sent more engines to our facility in 2011 than IMS Bearing failures~

997 WATER PUMP DOES NOT FIT 996. In my haste yesterday, I did not report this. When I ordered my pump from Sunset Porsche, I was told that Porsche now recommends the 997 pump for 996s. As it turns out the 997 pump will bolt right up. BUT the impeller is about 3/32" larger in diameter and will not turn inside of the housing. Had I not checked for free rotation upon installation and fired up the car it would have been a disaster. When I called Sunset and reported this, I was put on hold for quite a while after which the parts guy came back after checking and apologized and did confirm that the 997 pump will not work in the 996 (MY'03 anyway). He sent out the correct pump. So, my car is not back together. I asked for a thermostat gasket to be sent with the new pump. Now I'm reading that I may need a special tool to remove the thermostat to look for that tiny piece of plastic that broke off from the old water pump impeller. Do I need a special tool?

You can make that "special tool" from a piece of pipe. http://986forum.com/forums/general-d...hermostat.html

If I were you, I would replace the thermostat housing and the thermostat with the LN low temp setup. I have it, it works great and it may help to prevent any head cracking do to a slightly lower operating temp. Just a thought. My car is an 03 also. To answer you question, you do need a tool to remove the stat from the housing but you should not need to do that to find the plastic. good luck.

Thanks all for the help and input for this anxiety provoking situation. One more question. The plastic fragment is about the size of a pinhead. Do I still need to be hyper concerned or is there a size larger than pinhead that will more likely clog the head cooling passages. What is the problem causing size of fragments?Do you think I might be OK if I can't find and retrieve the culprit?

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A pin head? What size pin? Seriously, I doubt a pinhead size piece of plastic will cause any issue. Can you take a pic of the old wp to show us exactly what size you are referring to?

I took some photos but i can't attach them for some reason. I've been messing with this computer all morning. So, my best description is: width= the size of the taper on the edge of the impeller blade. length =2X the width OR ( slightly less than 1/16"X 1/32") OR 1mmX 2mm aprox

My water pump gave no signs of pending death...it just exploded. I'm thankful it was plastic. Preventative replacement is good...but I would stick with stock.

Can you share with us the exact part number you used in the end and cost for the part, I mean the proper 996 version of the pump, and also for the thermostat gasket if it is required. did you use special precaution to refill the cooling system, to avoid air bubble inside the system ? I think I'm gonna tackle this update on my car next month.

I don't know the parts numbers, but you can get them off of Pelican Parts website. On Porsche parts they use the Porsche numbers. As far as bleeding the system, my mechanic friend is coming over to bleed it. He has the device to do that. I wondered about that also.

please report to us how the bleeding was done, i am particularly curious about that

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If you just replace the wp and you don't empty the entire system, purging the system takes time but is not that difficult. You fill up the coolant tank to the max level, pull the purge valve on the coolant tank cap so that it is open, start the car and move it to a steep graded area with the *** end of the car higher up. (you could use jackstands but I have a steep driveway), watch the coolant flow from the tank into the engine, shut the car off, put in more coolant. Repeat this a few times over a few hour period.

I bought my Porsche coolant pump from Flat6 (Jakes outfit) last year - part #996 106 011 55.