4 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHCoolant leak from expansion pressure cap
Leading reported evidence
Use pressure
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
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0
Unsuccessful attempts
1
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Read evidence and context
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Performed · outcome unconfirmed · Original poster
I had cycled the coolant a while back and used pressure to evacuate system and vacuum pump to refill, no drama.
Leading evidence: 'Use pressure' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check blue cap, the number is there' (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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Suggestion
Separate from that, are you using the original expansion tank cap?
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.
4 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
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Generation: 20261027T140027Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
OK my fine friends,opinion required.
Changed water pump, thermostat and expansion tank as part of precautionary ongoing mechanical restoration (done everything around the engine but to date not had to drop it).
I had cycled the coolant a while back and used pressure to evacuate system and vacuum pump to refill, no drama.
i had been slightly worried that the coolant was cloudy when drained into tub (a cup full looks clear just in quantity), not oily, and certainly not gooey mess. And no real sign of mayo in oil filler cap and oil looks good.
Went to flush and refill post changing parts.
1. Couldnt get a vacuum to help fill
2. Manually filled and bled
3. When engine coming up to temperature (while burping) noticed that coolant is slightly bubbly on surface (didn't get pic!)
4. When engine up to temperature the coolant tank fills up and starts leaking out of underneath of one part of pressure cap on expansion tank
5. When cooled, expansion tank needs topping up little (ie I think has been filled to correct level, plus the bit that leaked out).
So I definitely have a leaky new expansion pressure valve, which likely cause of not getting vacuum... but worried the other signs (ie small bubbles on surface / over expansion when hot) are likely to be caused by either a blockage or, more likely, exhaust gases from a crack in the head (maybe just starting).
What do we think?
Use a kit to check for fumes in the coolant.
https://www.ebay.com/itm/186842143869
I would update the cap to the latest version just in case. I think it ends in 04. Check your blue cap, the number is there.
Just want to get the sequence right. You installed a new expansion tank and now you can't get it to hold a vacuum? Did you get the Porsche brand expansion tank or another brand? Separate from that, are you using the original expansion tank cap? What are the last two digits of the part number on that cap?
