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coolant tank scare?

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Advise appreciated


This morning as I was checking oil dipstick oil level I also added a little of Porsche engine coolant to my tank to get it to about 3-4 mm off the max level. I added some cause I wanted to keep it at this level, (have not added any since about 2 summers ago). Went out and drove for about 30 k, when got to destination I lost some coolant.... that's it I think the tank has cracked, so I bought some water to replace the fluid in order to get back home again. As is difficult to really see the level in plain sunlight, I added water, to my surprise just could add about 150-200ml max ?

Put the cap back again and started the engine, it never got hot (all the time the needle was in the 80 C mark) so I decided to drive back home, didn't lost any more fluid and engine temp was OK all the time, even if it was a warm day (29-30C)

At home took the plastic sheet beneath the oil and coolant caps, and noted that there was signs that coolant had gone by the overflow drain. Didn't lost any more fluid, but I extracted around 150 ml of coolant with a seringue to get it to the max level once the engine had somewhat cooled down. I replaced the cap some about 3 yrs ago, with the new one, I had the original and read somewhere that it could be a good idea to replace it, so I did.

Should I replace it again? Could it be just the cap malfunctioning?

I was planning to drive it again tomorrow around here to see if everything is normal (as it seems!).

Thanks in advance for any advise, I reatly will appreciate it.


Boxster 2.5 1998

Edited by Oldguy57
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Hello Loren, the cap number is 996.106-447.04

Could it be the problem? Should I replace it before driving it again?


More details about my car:

Boxster 1998, 2.5 manual, 100000kms bought about 5 yrs ago with 85000kms 

Edited by Oldguy57
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Hello again, finally it was easier for me to get a new pressure tank cap, as I have not lost any more fluid I plan to drive it again with a new cap and keep it on check. If the problem do not repeat I tend to think that it was caused by a malfunction of the cap, does it make sense? does a "loose" cap could do that, maybe I didn't tighten it enough?(when I added coolant, I don't think so but, could it be?)

Thanks again for your help!

Edited by Oldguy57
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So I replaced the cap with a new one, been driving it around for 2 times for about 70 kms, have not had any more fluid loss, engine temps stays around 80 C with the fans kicking in just a tad over 80 C as always, I still keeping an eye on it every time and at the level when it completely cools down and everything seems normal, for now.

I'll keep a close eye on it, but does it make sense to assume it was only a cap problem?

Thanks in advance for any feedback on this issue.

Have a great day!


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  • 2 months later...

New update; after more than 800Km after replacing the cap with a new one I have not had any issue with the coolant, so I assume it was only a cap problem.

Thanks Loren,for your advise, the cap is a common problem, and it was a 04 one!

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