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THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHExpansion tank cap - leaking
Leading reported evidence
Check on the right hand side of the engine compartment
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Suggestion
Also check on the right hand side of the engine compartment.
Leading evidence: 'Check on the right hand side of the engine compartment' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check on the right hand side of the engine compartment' (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 · Original poster
Dropping it off today to get it properly checked over, but hopefully it's just a dodgy cap.
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6 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
911uk: 1 discussions
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Generation: 20261027T022239Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Hi all,
My C4S is losing coolant at the moment - no obvious leaks on the floor. Something in the region of about a pint every 200 miles or so.
When the car is up to temperature I have noticed that there is a drip coming from the expansion tank cap, and today I noticed a hissing sound just like drops of water hitting something hot.
Do these caps fail just like that? Given the hissing sound, could there be another issue as well, as the water from the leaky cap seems to be collecting on the tank itself rather than dripping anywhere else.
It'll be checked out by my local indy this weekend/early next week but thought I'd ask around myself as well.
Expansion tanks and caps are well known for failing on older cars.
The tank and cap were both changed in design on later models.
Not that expensive to change over.
TB
Also check on the right hand side of the engine compartment. There is a water pipe that exits the block, rises, turns and then heads to the front of the car. This pipe rubs against the compartment body and leaks. Porsche have designed a new pipe and engine block flange that keeps the pipe well away from the body, has a 997 part number.
Also, the expansion tank itself is prone to crack.........
Ray :lol:
Thanks for your help - I can see it dripping out of the cap at a fair rate. It then goes into a little 'sink' on the expansion tank which has a drain hole connected to a pipe - which empties itself above the exhaust. This explains the hissing sound and also why I can't see a puddle on the floor...
Dropping it off today to get it properly checked over, but hopefully it's just a dodgy cap.
A bit of good 996 news - looks like it's just the cap. My Indy pressurised the system (and left it overnight), no pressure loss. Also no indication of any CO in the water.
One new cap, and it doesn't seem to have lost any more water
Phew!
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