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Old 12-07-2006, 09:25 AM   #1
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Question Coolant Resevoir Level Question

Since my last oil service about 1500 miles ago, the dealer topped off my coolant in the resevoir above max. I check it on a regular basis when its cold and today, before I drove the car, I checked the level and noticed it was about a 1/4" from the max line.

Is this normal under regular use? I thought this was supposed to be a "closed" system?
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Old 12-07-2006, 10:02 AM   #2
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If you are worried about leaks, one quick check is to pull up the carpet and the piece of wood below the carpet in the rear trunk and look for fluid. If you find some, the expansion tank has a leak. If you find fluid on the ground under your car, then you know it's a hose.

I do believe the system, even though it's a closed system, does evaporate a little. Also, very cold weather is going to reduce the volume of the coolant compared to temperate or hot weather... but not by much... probably what you're seeing.
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Last edited by RandallNeighbour; 12-07-2006 at 10:06 AM.
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Old 12-07-2006, 01:47 PM   #3
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Hi,

IMHO, if you have an early car and the Coolant Tank hasn't leaked, it's just because it hasn't leaked yet. The problem is not one of design, rather it stems from the type of Plastic used.

Over time, this plastic becomes unstable due to heat cycling. It off-gasses some of it's constituent chemicals resulting in a loss of plasticity, and subsequently cracks.

Back to your issue, you're correct, it is a Closed System, but it is also a pressurized system. The way that the system's pressure is regulated is to keep a specific air cavity in the Coolant Tank which is why the Fill mark is where it is.

As the Coolant heats and expands, it compresses this air cavity and at a certain point, pressure starts to build. But, if you reduce the size of this air cavity (by overfilling the system), you reduce the compressibility of it and the pressure rises higher than designed.

At this point, the system will seek to relieve the pressure and will likely seep Coolant (usually as steam) under the Coolant Cap seal, or past one of the system's Hose connections (which already aren't the strongest due to the Spring-type Clamps Porsche originally used).

A TSB directs that these Spring Clamps be replaced by Worm (Screw-type) Clamps whenever the opportunity presents itself such as when repairing, or draining the system. I suspect this is where the missing Coolant went, assuming that you eliminate a possibly cracked and leaking Coolant Tank as a cause.

A long-distance diagnosis is often very difficult, so while I don't think it's anything to worry about, I'd keep an eye on it for a couple weeks to confirm my speculation. Hope this helps...

Happy Motoring!... Jim'99

Last edited by MNBoxster; 12-07-2006 at 02:32 PM.
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Old 12-07-2006, 02:30 PM   #4
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Thanks guys for your invaluable advice! I'm going to pull the carpet and keep an eye on this...
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Old 12-08-2006, 11:35 AM   #5
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I have a 98 w 110000 miles. I just replaced mine. I was getting the low level light, fill it, get it again a week latter.
If the plastic degrades over time why wouldn't that be considered a "design flaw"?
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Old 12-08-2006, 12:14 PM   #6
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Call it whatever you like. Design flaw; low bidder manufacturing; inferior plastics used in manufacturing (wrong specs or substituted by low bidder without Porsche's knowledge), etc.

Here's a short list of the crappy parts on our cars that will go out every couple of years and won't be recalled and paid for by Porsche Cars N.A.:

Coolant Expansion Tank
Seat Belt Receptacles
Ignition Switch
Windscreen Clips

I'm sure there's more flimsy parts I am forgetting...
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