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Coolant Flush, Water Pump Replace, Coolant Tank, 160 Degree Thermostat

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Late 2004 Boxster Base Tiptronic with 45,000 miles

I have racked up 15,000 miles over the last 3 years of ownership. The coolant was flushed about a year prior to purchase. I think it's time to flush the coolant. I plan to buy the Airlift tool - it's a time vs cost issue, time wins.


I know from searching that JFP has recommended to others to replace the water pump as preventative maintenance on a car this age. Fair enough. Porsche pump, clean the mating surfaces carefully and:

1. Use gasket sealant or no sealant?


2. Should I replace the coolant reservoir even though I cannot find anything wrong with it?


I'll replace the thermostat at the same time.

3. Should it be the 160 degree thermostat?

3a. I notice that the car runs between 190 - 210 degrees (using Scangauge) most of the time in warm weather, so will the 160 stat be a benefit?


4. Which hoses should be replaced?


5. Anything else?


Since the start of ownership I've done mostly preventative and general maintenance with very few actual failures of any kind. With that being said, I think mileage is beginning to expose some common failures cropping up like what happened yesterday - the turn signal stalk won't hold in-place, so now I need to replace it but at least getting the 4-stalk version will give me the OBC functions.


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1. Use gasket sealant or no sealant? No sealant when I did mine just the new gasket which you will need to cut off the correct section. I like to lube the gaskets just a bit with silicone but that’s just me.
2. Should I replace the coolant reservoir even though I cannot find anything wrong with it? Well, just depends on your philosophy. Wait until it goes or do it preemptively. Mine went some years ago and it is a bit of a pita, and since your coolant will all be drained anyway, I would probably do it.
I'll replace the thermostat at the same time.
3. Should it be the 160 degree thermostat? Yes, that’s what I used. Car runs much cooler which is nice especially on hot days. I don’t think there is a performance benefit that I know of.
3a. I notice that the car runs between 190 - 210 degrees (using Scangauge) most of the time in warm weather, so will the 160 stat be a benefit? It will definitely run cooler.
4. Which hoses should be replaced? Just check for deterioration or signs of leaked coolant. I did not replace any at the time I did mine and all is still good at 18yrs and 110k mi.
5. Anything else? Get the latest coolant reservoir cap and follow the procedure for filling and bleeding. I like to use the vent valve open for a few days to bleed the air then refill after all cools off. Otherwise it can be a huge mess. Use the right coolant, doesn’t have to be Porsche but the correct type, which I cannot recall offhand.
Someday I hope to do the new stalk as well but haven’t gotten there yet!

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I would just add the replacement of the serpentine belt if it's still the original one.

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Thank you both for your replies!


The serpentine belt was replaced on a major service that was done within 2 months of purchasing, which included IMS, RMS, AOS, oil & filter, trans fluid & filter, plugs, air filter, cabin filter. By this time the engine oil and filter had been changed twice since my purchase, once immediately including inspection of filter and then again with the major service because I'm nuts.


At the moment I'm on the fence regarding replacing the coolant reservoir. I'll probably do it, but the other side of my brain is saying that I could do it later and wouldn't require much fluid replaced since it's "at the top" of the system. So a question I have is, does draining and refilling the system involve enough stress on the reservoir that more often than not a failure could occur?? If the law of averages favors failure, then I'd have to replace it.


Peace of mind is something I preach to others on matters such as this, but I've already replaced the brakes, plugs, and coils last month, now this, and then the Spring Tour isn't really cheap either.


Arrgg! I guess I just talked myself into it. What's another $300. I keep telling myself I just won't go out for dinner as much, but that never happens either. See?? This is cheaper than therapy and totally drug free! I'll save a little for now by not replacing the turn signal switch cluster for a while.


crwarren11, when you say your car runs cooler with the 160 stat, does it run cooler even after long distance driving? I ask because my car runs in the low 190's at 70mph while on trips to neighboring states, so I wonder if it flows more coolant through it than the 180 stat can do while they are open?

Edited by ttocs

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So I opened up around the coolant reservoir to assess its condition prior to ordering a new one. I was expecting yellow brittle plastic like many photos I've seen posted everywhere, but instead I'm presented with what appears to me to be a reservoir manufactured in mid 2004 (date code) that is in immaculate condition! No yellowing at all.


1. What causes the yellowing?

2. When a reservoir is in condition this good, is it really as much of a concern for failure as one that has obvious signs of aging?


Also, there are no signs of seepage so far. I'll be inspecting the bottom of the water pump for "crusty" stuff next chance I get.


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It does look to be in good shape. I don’t recall mine being yellowed. It was simply cracked and leaking annoyingly into the trunk. Mine lasted 8yrs and 80k mi mostly in Southern California. It has now been another 10yrs on the new one but only 30k mi. 


As for the running temp I would say that it runs cooler for longer at the start especially. It is usually right at the 180 mark on the gauge and after a long time it might creep up to that spot right between the 8 and 0 but I have yet to see it go higher than that after the new thermostat. I used to consistently run at the far right side of the 0, so guessing around 195F, with the old thermostat.  It makes sense that eventually after a long run that the new thermostat is not going to do anything to help. 


Another important thing to consider for running temp is cleaning out the front radiators. It is easy to remove the front bumper to access them. There is a diy in this forum. 

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Thanks again crwarren11! Cleaning out the front radiators is something that is on the countdown list of things to be done prior to our PCA Chicago Spring Tour in June.


Prevention of catastrophic failure is easy for my brain to cope with, like the IMS. However, everything I've checked on the cooling system is in perfect condition including the coolant fluid (see photo) which matches the appearance of brand new Porsche coolant. It seems a shame to replace any of it, but I will.



I placed the order for the water pump and gasket, stat gasket - I ordered the 160 degree stat from LN Engineering, Porsche hose clamps - yes I know some use other types but the originals have been perfect, and the Porsche coolant. I'll pickup everything in a couple days when one of the out-of-stock hose clamps comes in. Yes I'm paying a little more than ordering online which is almost totally offset by not paying for shipping, but I really appreciate their willingness to help me at every turn and taking every opportunity of applying discounts to the max they are allowed. And, they have always supplied the latest version of every part I've purchased, as opposed to many heavily discounted older versions of some parts available online (not Sunset, they have the right stuff). Sunset is my favorite for online and phone orders.


I am not replacing the reservoir yet. The water pump seems to me like a good candidate for routine mileage based maintenance. Being at 45,000 miles, and considering the age, and since the thermostat is being replaced, I figure pump and stat get replaced together. But the tank is up top and easy to monitor, so . . . . 


I read Ahsai's great writeup on getting the last drop of coolant out of the system and will be using that as my guide. Thanks Ahsai!

Edited by ttocs

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I think you'll find consensus that the water pump is a very good thing to replace as preventative maintenance.  Too many stories of these cars with blown pumps and expensive repairs.  If I remember correctly, most recommend every 30k mi, which for the price of the part and the ease of replacement, seems like a very good thing to do.  I had the same rationale for doing the low-temp thermostat at the same time.  I mean, why not?


I agree with your decision not to replace the reservoir for now.  After looking back at when mine went out, you have much fewer miles and I'm guessing much less exposure to the elements than what mine had been through.  Only other thing I would recommend is confirming that you have the latest revision of the reservoir cap.


Keep us posted!


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