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Old 10-29-2011, 12:42 PM   #1
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Intermintent coolant loss at expansion tank

So I know that the expansion tank is a known problem and I have had the intentions of swapping it out, but just have never got around to it. I had a leak about a year ago and I swapped out the cap because it was cheap and easy and I was hoping it might prevent extra pressure which might be causing the tank to leak. It didn't work, but strangely about 2 weeks later, the leak stopped.

Fast forward a year later and the tank started leaking like crazy again. I had to add about a liter of coolant each time I went to drive the car. This went on for about a month and I drove the car several times a week.

Topped up the tank like I had been doing, and now it hasn't leaked at all since. Has anyone else experienced something like this? I know the solution is to just replace the stupid tank, but I am still curious as why it seems to leak intermittently.

Car as never overheated and the temperature gauge has never got higher than usual..
00 S Triple Black- Smoked lights, Tinted windows, Stainless exhaust, IwireP ipod cable, desnorkled, painted bumperettes
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Old 10-29-2011, 03:26 PM   #2
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Don't mess around with the cooling system on these cars. One brief overheating can be
disastrous. When you dump that much coolant, overheating is just around the corner. find out whats wrong with it and fix it.
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2000 Boxster 2.7l red/black

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1973 Opel Manta
1969(?) Fiat 850 Convertible
1979 Lancia Beta Coupe
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1989 Porsche 944
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Old 10-29-2011, 03:29 PM   #3
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They develop hairline cracks in the reservoir. Changes in temperature and volume of coolant could make it leak more sometimes than others. I agree with the above - you do not want to chance overheating your car even a little.
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Old 10-31-2011, 11:13 AM   #4
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It might just be because the cooler weather makes lesser demands on the cooling system and the tanks becomes pressurized to a lower level when it's cool. Another thing is a partially empty tank provides a sort of air cushion. When the water expands it won't build as much pressure as when the tank is totally full. Mine didn't start leaking until I topped it off one day during the hot weather. Next drive = big leak on garage floor and a $600 repair bill. Now I don't fill it to the max.
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