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why is my coolant draining out? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

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YOUR RESEARCHwhy is my coolant draining out? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Leading reported evidence

Fill expansion tank

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Suggestion · Original poster

Issue: When attempting to fill the expansion tank with coolant, it quickly drains out through the overflow hose.

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why is my coolant draining out? - 986 Forum - The Community for Porsche Boxster & Cayman Owners
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Leading evidence: 'Fill expansion tank' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Fill expansion tank' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.

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Replace already, they are certainly due

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Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.

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Suggestion

If they haven't been replaced already, they are certainly due.

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why is my coolant draining out? - 986 Forum - The Community for Porsche Boxster & Cayman Owners
Frequently discussed actions (2)

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Fill expansion tank

No successful repair reported for this finding.

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Reported fixes
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Unsuccessful attempts
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Discussions
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Discussions that contain suggestions
1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion · Original poster

Issue: When attempting to fill the expansion tank with coolant, it quickly drains out through the overflow hose.

Original post Read captured discussion
why is my coolant draining out? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Replace already, they are certainly due

No successful repair reported for this finding.

0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that contain suggestions
1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion

If they haven't been replaced already, they are certainly due.

Original post Read captured discussion
why is my coolant draining out? - 986 Forum - The Community for Porsche Boxster & Cayman Owners
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Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.

6 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.

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Generation: 20261026T130754Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources

POST 1 / ORIGINAL POSTEROriginal post

Car: 1997 Boxster 2.5 base. 95k miles. Issue: When attempting to fill the expansion tank with coolant, it quickly drains out through the overflow hose. Background: During an Autocross event today, I observed coolant leaking under the rear passenger wheel well after several hot sessions. Upon closer inspection, I noticed coolant also steaming off the rear trunk, originating from the expansion cap. The area beneath the expansion tank was also wet, and the coolant tank was nearly empty (95%). I decided to tow the car back home and tried refilling the tank. However, as I filled the expansion tank, the coolant immediately drained through the overflow hose. I recall adding a small amount of coolant to the tank the day before, raising concerns about whether this contributed to the issue. note: Two weeks earlier, I tracked the car at a local PCA DE event without encountering any problems. Considering there had been a recall/upgrade for the tank and cap, I opted to order a new expansion tank kit from Pelican. Do you think this was the right decision?

POST 2Original post

Yes. If they haven't been replaced already, they are certainly due.

POST 3Original post

Agree also. It should only run out of the expansion tank if it overheats and boils over. If you’re just putting it in and it’s draining straight out it’s not the overflow tube.

POST 4 / ORIGINAL POSTEROriginal post

Thank you all. I will pressure test it this weekend to identify the exact issue, the parts should be here by then.

POST 5Original post

Quotes source post: 658442

Tell us you ordered the PORSCHE tank. Tell us you didn't order the URO tank. Tell us.

POST 6Original post

By German law, all the plastic on this car is biodegradable. New expansion tank at 20 years for sure.

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