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2017 Jeep Grand Cherokee — coolant slowly disappears without an obvious leak

ManualDetailerCommunity StarterAug 25, 20262017 Jeep Grand Cherokee LimitedWashington DC
2017 Jeep Grand Cherokee Limited, about 114,500 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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2018 Jeep Grand Cherokee Limited

$24,000

Denver, CO

13 replies

RustBeltGarage568Community StarterCommunity StarterAug 25, 2026permalink
This is usually cheaper to test than to guess. If a shop can't duplicate it on the 2017 Jeep Grand Cherokee, bring a video plus freeze-frame data, not just a story. Don't erase codes until someone who can help has seen them. If you share a photo of the worksheet, easier to sanity-check. Doing the boring step first on purpose.
RustBeltGarage568Community StarterCommunity StarterAug 25, 2026permalink
Ask what changed right before it started. Write temp, speed, and in-gear vs coast when the 2017 Jeep Grand Cherokee does it — then decide on parts. Don't erase codes until someone who can help has seen them. Happy to compare notes if your setup is different. I keep a notes app thread for this now.
RoadTripTuner735Community StarterCommunity StarterAug 25, 2026permalink
Log the conditions before you spend. Loaded-suspension checks on the 2017 Jeep Grand Cherokee catch play that a wheels-hanging inspection misses. 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. Had a similar mess a couple years ago and that's what finally sorted it. Cold start is when I can actually reproduce it.
RustBeltWrench696Community StarterCommunity StarterAug 25, 2026permalink
Start with the test that can prove you wrong. Loaded-suspension checks on the 2017 Jeep Grand Cherokee catch play that a wheels-hanging inspection misses. You'll know quickly if you're on the wrong tree. Had a similar mess a couple years ago and that's what finally sorted it. If it repeats twice more I'll book time.
OldSchoolCommuter974Community StarterCommunity StarterAug 25, 2026permalink
If it were in my driveway, swap the cheap/easy piece first on the 2017 Jeep Grand Cherokee and see if the fault moves. Don't erase codes until someone who can help has seen them. If you share a photo of the worksheet, easier to sanity-check. I'd rather be boring and correct. I'm keeping receipts and dates in one folder.
RoadTripTuner735Community StarterCommunity StarterAug 26, 2026permalink
Ask what changed right before it started. Write temp, speed, and in-gear vs coast when the 2017 Jeep Grand Cherokee does it — then decide on parts. Don't erase codes until someone who can help has seen them. Learned this the expensive way on a previous car. Might be overthinking it, but I'd rather overthink than overspend.
EVHauler666Community StarterCommunity StarterAug 26, 2026permalink
Start with the test that can prove you wrong. Capture voltage while the 2017 Jeep Grand Cherokee is actually failing — after it restarts you've lost the clue. Save the big job until that test fails. Time, temperature, and whether it's in gear are the notes that actually help a shop. Happens in gear, not in park, for what that's worth.
OldSchoolCommuter974Community StarterCommunity StarterAug 27, 2026permalink
Quick add on that: Capture voltage while the 2017 Jeep Grand Cherokee is actually failing — after it restarts you've lost the clue. Don't erase codes until someone who can help has seen them. On “coolant slowly disappears without an obvious leak,” that was the fork that mattered for me. Happy to compare notes if your setup is different. I'll update if anything new shows up.
RustBeltGarage568Community StarterCommunity StarterAug 27, 2026permalink
Agree — and I'd add this: Get a real battery/charging test on the 2017 Jeep Grand Cherokee, not just resting voltage, before blaming a module. Save the big job until that test fails. If you share a photo of the worksheet, easier to sanity-check. Cold start is when I can actually reproduce it.
OldSchoolDIYer812Community StarterCommunity StarterAug 27, 2026permalink
Asking because it changes the advice: Get a real battery/charging test on the 2017 Jeep Grand Cherokee, not just resting voltage, before blaming a module. Save the big job until that test fails. This is from a 2017 Jeep Grand Cherokee in Washington DC with 114,500 miles. Run the total, not the monthly, before you commit. That's coming from doing this as an owner, not a shop. I'd rather pay for diagnosis than a second guess-repair.
EVHauler666Community StarterCommunity StarterAug 28, 2026permalink
I hear you, though I'd still want a second check. Move a coil or plug on the 2017 Jeep Grand Cherokee if it's cylinder-specific and see whether the code follows. You'll know quickly if you're on the wrong tree. Write the result down so the next test isn't a repeat of the last one. I'd sleep better after that step, even if it finds nothing. I'd rather pay for diagnosis than a second guess-repair.
EVHauler666Community StarterCommunity StarterAug 26, 2026permalink
Intermittent stuff lies if you only catch it once. A pressure test beats staring at a dry driveway if the 2017 Jeep Grand Cherokee is losing coolant with no puddle. Don't erase codes until someone who can help has seen them. On “coolant slowly disappears without an obvious leak,” that was the fork that mattered for me. Time, temperature, and whether it's in gear are the notes that actually help a shop. Next check is the cheap one I can do in a driveway.
RustBeltGarage568Community StarterCommunity StarterAug 26, 2026permalink
I wouldn't throw parts yet. Get a real battery/charging test on the 2017 Jeep Grand Cherokee, not just resting voltage, before blaming a module. If the cheap test changes it, stop and reassess. Post the numbers (or the code) and people can get more specific. Heat soak after errands is the other window.
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