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Porsche Club GB

Expansion Tank - black thingy behind cap!!

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8 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW

Discussion summary

YOUR RESEARCHExpansion Tank - black thingy behind cap!!

Reported or suspected cause

some kind of pressure release valve as it appears

Suggestion or failed attempt

No successful repair reported for this finding.

0
Identified cause
1
Suspected cause
0
Reported fixes
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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.

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

Suspected cause · Original poster

(suspect some kind of pressure release valve as it appears to be sprung) with a wire that appears to be for the purposes of pulling it up.

Expansion Tank - black thingy behind cap!!
Frequently discussed work

Run car

No successful repair reported for this finding.

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Reported fixes
0
Unsuccessful attempts
1
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

but you can run the car for weeks with the bleed valve open.

Expansion Tank - black thingy behind cap!!
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Leading evidence: 'some kind of pressure release valve as it appears' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'some kind of pressure release valve as it appears' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Run car' (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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1 matching discussions · 8 captured posts examined · 0 partial discussions

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Run car

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context

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.

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

but you can run the car for weeks with the bleed valve open.

Expansion Tank - black thingy behind cap!!

Run round

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context

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.

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

......actually, once warm, they all run round with the bleed valve open all the time as the pressure in the cooling system forces it open anyway.

Expansion Tank - black thingy behind cap!!
Frequently discussed actions (2)

These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.

Run car

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 · Original poster

but you can run the car for weeks with the bleed valve open.

Expansion Tank - black thingy behind cap!!

Run round

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

......actually, once warm, they all run round with the bleed valve open all the time as the pressure in the cooling system forces it open anyway.

Expansion Tank - black thingy behind cap!!
Reported and suspected causes (1)

These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.

some kind of pressure release valve as it appears

No successful repair reported for this finding.

0
Identified cause
1
Suspected cause
0
Reported fixes
Read evidence and context
Discussions that suspect a cause
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.

Suspected cause · Original poster

(suspect some kind of pressure release valve as it appears to be sprung) with a wire that appears to be for the purposes of pulling it up.

Expansion Tank - black thingy behind cap!!
Coverage and how to read this overview

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.

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

  • Porsche Club GB: 1 discussions

0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.

0 acknowledgements have no verified action link; they do not establish a repair result.

Generation: 20261026T191851Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources

POST 1 / ORIGINAL POSTEROriginal post

Hi - I'm a Newbie to this site. I've got a 996 C2 Cab 2000/W that I have had for about 10 months. Behind the expansion tank filler cap there is a black thingy! (suspect some kind of pressure release valve as it appears to be sprung) with a wire that appears to be for the purposes of pulling it up. The housing it sits in has ridges on it that seem to be for the purpose of locating and holding the 'wire puller' so that it holds it up/open. Q1. What is it? Q2. What position should it be in - up or down? Apologies this is not very technical. Any pointers gratefully received. Cheers

POST 2Original post

It is used for bleeding the air out of the cooling system, and should be in the 'down' position in normal use. The bleeding process is quite a complicated procedure, and would frighten the life out of me to do it, as it involves revving the b*ll*cks off it several times (under no load) over quite a long period. Apparently there are several pockets in the water jacket that can trap air after a coolant change.

POST 3 / ORIGINAL POSTEROriginal post

Thanks Richard....much appreciated. Kind Regards ____________ Keith C2 Cab Tip Silver

POST 4 / ORIGINAL POSTEROriginal post

Actually, the bleed process is complicated... but you can run the car for weeks with the bleed valve open. Cup Cars do this all the time.

POST 5Original post

......actually, once warm, they all run round with the bleed valve open all the time as the pressure in the cooling system forces it open anyway. Check it out next time your engine's fully warm - the bleed valve will be wide open. Ian W

POST 6 / ORIGINAL POSTEROriginal post

Thanks Loren and Ian W. This is all part of my diagnosis as to why I am losing coolant and signs of an oil leak (oil on top of engine behind and to the right of the oil filler cap. Needless to say I am starting to fear such things as RMS!!!

POST 7Original post

berrick First the good news - oil on top of the engine isn't RMS. If that was starting to fail you would be seeing oil on the bottom of the engine, dead centre, where it joins the gearbox (i.e. the front of the car / back of the engine bay). Bad News? Most likely cause of oil on top of the engine is the oil separator and/or return bellows (had 3 of these go on my 3.4). Good news again - bellows is only about 65p (and I'm not exaggerating much) but - bad news - it's a complete pig to get at. A good independent will want 3-4 hours (IIRC) to fit bellows and separator canister if necessary. Most likely candidate for coolant loss would be the expansion tank itself. These have a nasty habit of cracking along the seam - right where you can't see it towards the back of the engine bay - and dumping coolant all over the place when the engine's really warm. They then come over all innocent and mended-looking as soon as you pull up and the car cools down. Sneaky little blighters. Hope this helps Ian W

POST 8 / ORIGINAL POSTEROriginal post

Thanks again Ian W. There is an independent near me Wrightune in Wallingford (saw a recommenddation on this forum for him) who I am planning to get to do the service that is due now (although I am going to have to wait until first week in June becuase he's so busy!) - but he's offered to stick it up on a ramp for me and have a look. Thanks again for your A&G

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