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1987 Porsche 911 — coolant slowly disappears without an obvious leak

HybridDaily9Community StarterMay 16, 20261987 Porsche 911 Carrera 3.2New Jersey
1987 Porsche 911 Carrera 3.2, about 153,500 miles. The reservoir goes from full to low over several weeks. No puddle, oil looks normal, and I cannot find dried coolant around the hoses. Is a pressure test the next logical move?
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6 replies

HybridDaily9Community StarterCommunity StarterMay 16, 2026permalink
OP update: scanned the 1987 Porsche 911 again and still only have the one pending code, no new lights. If the story changes I'll post the new data.
HybridDaily9Community StarterCommunity StarterMay 16, 2026permalink
Cleared nothing. I want service to see the alert on the 1987 Porsche 911 first. I'd rather pay for diagnosis than a second guess-repair.
TrackTraveler521Community StarterCommunity StarterMay 17, 2026permalink
Ask what changed right before it started. Loaded-suspension checks on the 1987 Porsche 911 catch play that a wheels-hanging inspection misses. That's the branch I'd chase this week. Had a similar mess a couple years ago and that's what finally sorted it. No warning lights, which is why I'm documenting it.
ShopDriverCommunity StarterCommunity StarterMay 18, 2026permalink
Same neighborhood, different next step: Move a coil or plug on the 1987 Porsche 911 if it's cylinder-specific and see whether the code follows. Save the big job until that test fails. On “coolant slowly disappears without an obvious leak,” that was the fork that mattered for me. Just my two cents from doing this recently. This is the filter I use when the thread starts repeating itself. Parking it somewhere I can hear it better next time.
WeekendGarageCommunity StarterCommunity StarterMay 17, 2026permalink
Intermittent stuff lies if you only catch it once. If a shop can't duplicate it on the 1987 Porsche 911, bring a video plus freeze-frame data, not just a story. That's the branch I'd chase this week. On “coolant slowly disappears without an obvious leak,” that was the fork that mattered for me. Verbal 'we'll take care of it' is not a plan. I'm in no rush to be a hero on it.
ColdStartCamper961Community StarterCommunity StarterMay 17, 2026permalink
I wouldn't throw parts yet. Swap the cheap/easy piece first on the 1987 Porsche 911 and see if the fault moves. That's the branch I'd chase this week. This is from a 1987 Porsche 911 in New Jersey with 153,500 miles. Keep sale price, fees, and rate as three different conversations. No warning lights, which is why I'm documenting it.
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