flashing today and the reserve tank is quite low. The dealer is closed and won't open until Monday - but it's like 90 degrees today and 83 tomorrow (which in MN in Sept is super awesome). Can I just go up the local Napa and get some coolant? And if so, what is the recommended brand/type and it's a 50:50 mix, right?

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John from MN
flashing today and the reserve tank is quite low. The dealer is closed and won't open until Monday - but it's like 90 degrees today and 83 tomorrow (which in MN in Sept is super awesome). Can I just go up the local Napa and get some coolant? And if so, what is the recommended brand/type and it's a 50:50 mix, right?

There is a concern of mixing the "wrong" anti-freezes and the coolant gelling.

If the coolant tank level is low there's a leak. Even if you have the right anti-freeze I'd advise you to avoid using the car to avoid the risk of subjecting the engine to localized overheating. If the system can't hold coolant it can't hold pressure and it is the pressure that developes as the coolant gets hot that prevents boiling of the coolant at the hottest spots in the engine. If this happens localized overheating can occur and this can lead to collateral engine damage.

Now the leak can be the cap. My 2002 Boxster's coolant tank got so low the warning light came on. Because I didn't know where the leak was and didn't want to waste real Porsche anti-freeze (I have a jug for just in case) I added nearly a gallon of distilled water. Around a month later the low level warning light was on again. This time I spotted a bit of condensation on the underside fo the rear trunk lid that covers the fluid access bay. I removed the bay floor and looked for any leak sign but didn't see any. I topped up the level with more distilled water and made a tent of aluminum foil and covered the bay and brought the engine up to temperature then shut off the engine. After a few minutes there was condensation on the foil. I decided to throw a new cap at the symptom and the level stopped dropping. Seems the original cap (part # ending in "00") can let vapor escape. Since it is only water vapor the anti-freeze remains and the distilled water didn't dilute the coolant.

Even if there is a real loss of coolant it won't hurt in an emergency to just top up the level with distilled water. If there is a leak then after the leak is found and fixed you can have the coolant drained and the system refilled with fresh coolant. This helps prolong the water pump life (the anti-freeze is water pump seal (and maybe bearing) "friendly") (the original water pump in my Boxster lasted 172K miles) and helps keep the hoses in good shape. The hoses of my 15+ uyear old Boxster are still in good condition and my car has covered around 315K miles.

Is the cap that can be the issue number 996-106-447-00? And cap number 996-106-447-01 is the improved replacement?

Well what Marc said could be right. I lost some coolant because my water pump was "sweating" coolant from the seal because of the heating and cooling. I never saw any fluid on the floor so it may not be serious.
As for the right coolant goes, using "Porsche" coolant will certainly not do harm to the components but you don't really have to. Rather than open a discussion on the board about what is the right coolant or not here is a link from our resident a Porsche expert.

[www.pedrosgarage.com]

obviously that has to be addressed. Which is fairly odd because I have no fluid on the garage floor. Also, I had driven it the previous day and put over 100 miles on - and the temp was consistent with where it always runs - and the light never came on. The light only flashed when I first started it up yesterday.

The coolant tank is very low, nearly empty. I did check the cap and the number ends in 00 - so your theory could be true.

What I'm hearing is that I could either use one of the Porsche approved coolant or just add distilled water. In addition, I should replace the cap since it's an old part number and a known cause for issues. If it is just the cap, the only thing that escaped was water and currently, the ratio is now greater than 50:50 tending toward more coolant, and adding the distilled water will put it back into balance.

Do I have that correct? I will have to bring it in to the dealer in next 30-45 days to prep it for winter storage.

The light comes on to tell you your fluid is low not that it is overheating. Obviously you must add fluid.
I would change the cap, add a premix of 50/50 to top it up, drive around and check the level once a week until you put it away.
If the fluid stays up, you just saved a trip to the dealer.

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John from MN
obviously that has to be addressed. Which is fairly odd because I have no fluid on the garage floor. Also, I had driven it the previous day and put over 100 miles on - and the temp was consistent with where it always runs - and the light never came on. The light only flashed when I first started it up yesterday.

The coolant tank is very low, nearly empty. I did check the cap and the number ends in 00 - so your theory could be true.

What I'm hearing is that I could either use one of the Porsche approved coolant or just add distilled water. In addition, I should replace the cap since it's an old part number and a known cause for issues. If it is just the cap, the only thing that escaped was water and currently, the ratio is now greater than 50:50 tending toward more coolant, and adding the distilled water will put it back into balance.

Do I have that correct? I will have to bring it in to the dealer in next 30-45 days to prep it for winter storage.

The "00" cap leaking may be a theory but it is based on my experience with this twice, once with my Boxster (6 or 7 years ago) then more recently with my Turbo. And I have lost count of the number of owners who've replaced the coolant cap to address inexplicable loss of coolant.

If there is no sign of any coolant loss from the water pump, any hoses/connections, the radiators, or the underside of the coolant tank, the odds are high the loss is via the cap. If you want to go to the trouble you can confirm the cap is the likely source but it requires topping up the coolant tank with distilled water, cleaning the cap (rinsing under hot tap water), cleaning the threads of the tank and the surface where the cap seals against the tank, installing the cap and properly tightening it down then creating a tent foil and placing this over the fluid access bay then running the engine enough that the coolant temperature gets hot enough (at least 212F) to cause the radiator fans to come on. At this point shut off the engine and wait. After a few minutes check the foil tent over the fluid access bay. If you see any condensation it is most likely from the cap. The tank could possibly be the source but my admittedly limited experience -- one tank that of my Boxster -- is under these "test" conditions the tank opens up and gushes hot coolant to the ground.

Regarding the water pump: There can be a bit of coolant loss past the water pump seal. (This is one reason why the Porsche anti-freeze is best as it has seal friendly compounds.) My info is while there can be a sign of a leak, white anti-freeze residue, there should not be any signs of wetness. The amount of fluid loss past the water pump seal is minimal. I have driven 5K miles in some of the hottest temperatures this side of Hell and the coolant system -- even with the coolant temperature at 226F -- has never lost any significant amount of coolant. The most likely time coolant will be forced out past the water pump seal, or past a bad cap, or through a split in the coolant tank, or anywhere else there is a leak, is when the engine is shut off hot enough the radiator fans are running. (As I mentioned above.) The heat load of the engine raises the coolant temperature -- which is 212F at the time the fans come on at low speed; if they come on at high speed the temperature is 216F; which in turn raises the cooling system pressure.

You can pick up some coolant test strips and if you can find some way to get a strip down in the coolant test the coolant. If the the strip indicates an excess of anti-freeze then you can add distilled water. If the strip indicates the anti-freeze to water ratio is balanced then the system is losing coolant which should be addressed. In the meantime you can just add distilled water unless you expect the car will be exposed to extreme low temperatures before you can get the anti-freeze to water ratio back to optimum. 'course, you can add distilled water then run the engine a bit to mix the cooant up and test with a strip to find out just what level of protection the coolant offers. The protection level may still be quiet sufficient.

If you have the car in to address a leak my advice would be at the same time just have the old coolant drained and refilled with fresh coolant. This ensures the anti-freeze to water ratio is optimum and the corrosion protection/seal friendly compounds are back to maximum strength.

should not be any signs of wetness." Are you saying a little white residue is normal, or is that cause for concern? I have seen white residue on occasion, but never a lot - and when I topped off the resevior today, it was down only about 1.5 quarts. I also ordered a new cap that should be here by Thursday.

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John from MN
should not be any signs of wetness." Are you saying a little white residue is normal, or is that cause for concern? I have seen white residue on occasion, but never a lot - and when I topped off the resevior today, it was down only about 1.5 quarts. I also ordered a new cap that should be here by Thursday.

What I was told ws that some white residue on the water pump casting is ok. Not much but some. However, there should never be any signs of wetness.

With this residue being acceptable it would appear only very little coolant could escape -- probably under the most severe (so to speak) conditions -- and that is shutting off the engine while the radiator fans are running. As I touched upon in a previous post the fans run when the coolant temperature gets to 212F and it can be even hotter. (Under some conditions I have oberved the coolant temperature of my Boxster reach and stay at 226F, this when driven in a spirited fashion on a mountain road in hot (90F+ weather) or when just driven in very high (in one particular case 116F) ambient temperature.) If the engine is shut off at this point the fans of course stop running and the water pump no longer spins and coolant is not being circulated. The heat load of the engine raises the coolant temperature further and it is already at the boiling point (or above). Cooling system pressure can climb. As some of us have experienced the cap can under some conditions allow some vapor to escape though this is due to a short coming in the cap. However, at the other end of the engine at the water pump end it is possible some coolant could be pushed out between the water pump seal. But because the coolant temperature is so high and the engine -- including the water pump -- is so hot the water evaporates just a short distance from the leak and leaves behind the anti-freeze residue in the form of a white stain. It won't, should not, extend very far down the casting.

Any wetness is a sign the leak occurs at other times, at lower temperatures and pressures, and is a sign the water pump is not healthy. In the case of my 996 Turbo on a hot summer day running errands with my Mom in the car as I was helping her in the car at the store I caught a whiff of anti-freeze. I know this is a sign of a coolant leak. After I dropped Mom off at home I drove the car over to the dealer and the tech put the car on the lift and at the water pump we found a crusty blob of greenish residue under the pulley. And the blob was damp. I booked the car in for a new water pump.

If you are worried about the water pump top up the coolant level but do not overfill. Then run the engine enough to get it hot to the point the radiator fans are coming on on their own. (The A/C should be off.) Get the rear of the car in the air (I'd back my car up on a pair of Rhino Ramps) -- or arrange to have a tech put the car on a lift -- and raise RPMs to the point the fans come on then shut off the engine. Then wait a bit. Shortly after I did this with my Boxster the cooltant tank let go with a gush of hot coolant and you don't want to be under the car if that happens.

After a while check the water pump area. it should be dry. If there is any signs of wetness there's a leak and the water pump (and T-Stat) should be replaced.

Have to add -- sorry but I want to be sure I touch all the bases -- there can be at least 2 signs of a bad water pump. A leak is one sign and I covered that. Another is noise. In the case of my Boxster while the water pump showed no signs of any leaks and I don't believe there was even any sign of any residue it was noisy, produced a low volume rumbling sound. With the belt removed there was just the hint of play at the water pump drive pulley/shaft. The other accessory drives had no play. The belt had a sharp (inner) edge which is a sign the belt is not tracking properly and this can be due to bearing play which allows the pulley to be pulled out of position. I "diagnosed" water pump and buttoned the car up and had it flat bedded to the dealer for a new water pump/T-stat (and fresh coolant).

Get the latest cap ending in '04' and make sure it is not cross threaded and is snuggly tightened. This issue has been discussed on the 986forum and many owners have confirmed that this simple fix solves the problem. Me included. And use the real Porsche coolant. In this case it is worth the cost.

The cooling system capacity is about 5 gallons so replacing 1L of the stock 50/50 mix with water changes the overall ratio to about 52.6/47.4, which is totally acceptable.