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2024 Rivian R1S — brake fluid is old but still looks clean — buyer question from Orlando

HighwayDetailerCommunity StarterMay 1, 20262024 Rivian R1S Dual-MotorOrlando
Fluid looks clear in the reservoir but has been in the car for several years. Would you change based on time/moisture rather than appearance?
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11 replies

BoostDriverCommunity StarterCommunity StarterMay 1, 2026permalink
I'd want a measurement, not a hunch. Swap the cheap/easy piece first on the 2024 Rivian R1S and see if the fault moves. You'll know quickly if you're on the wrong tree. I'd want that in writing, not as a promise. I'd sleep better after that step, even if it finds nothing. This is the version I'd tell a friend.
HighwayDetailerCommunity StarterCommunity StarterMay 1, 2026permalink
I went back under the 2024 Rivian R1S and it only happens after a heat soak, not on a cold start. This is the version I'd tell a friend.
RustBeltDaily757Community StarterCommunity StarterMay 2, 2026permalink
Log the conditions before you spend. Get a real battery/charging test on the 2024 Rivian R1S, not just resting voltage, before blaming a module. That's the branch I'd chase this week. On “brake fluid is old but still looks,” that was the fork that mattered for me. If they can't show the line item, I assume it's hiding. This is me being the wet blanket on purpose.
PistonShopperCommunity StarterCommunity StarterMay 2, 2026permalink
If it were in my driveway, move a coil or plug on the 2024 Rivian R1S if it's cylinder-specific and see whether the code follows. If the cheap test changes it, stop and reassess. Write the result down so the next test isn't a repeat of the last one. Video is ugly but it shows the hesitation.
DealTraveler677Community StarterCommunity StarterMay 2, 2026permalink
This is usually cheaper to test than to guess. A pressure test beats staring at a dry driveway if the 2024 Rivian R1S is losing coolant with no puddle. Save the big job until that test fails. A shop burned me once by skipping that step. Not driving it hard until I know more.
RustBeltWeekendCommunity StarterCommunity StarterMay 3, 2026permalink
I'd push back a little: Move a coil or plug on the 2024 Rivian R1S if it's cylinder-specific and see whether the code follows. Don't erase codes until someone who can help has seen them. Not gospel, but it saved me a headache. Cold start is when I can actually reproduce it.
BoostGuy47Community StarterCommunity StarterMay 3, 2026permalink
That's a good start, but I wouldn't stop there. Get a real battery/charging test on the 2024 Rivian R1S, not just resting voltage, before blaming a module. Don't erase codes until someone who can help has seen them. I'd want a dollar figure or a measured spec, not 'should be fine.' I'd rather pay for diagnosis than a second guess-repair.
HighwayDetailerCommunity StarterCommunity StarterMay 2, 2026permalink
It did brake fluid is old but still looks twice this week, both times after sitting. No change in mileage feel. Not interested in a five-hour wait for a shrug.
HighwayDetailerCommunity StarterCommunity StarterMay 2, 2026permalink
Tried a second charger / second scan and the story on the 2024 Rivian R1S didn't change. Not driving it hard until I know more.
PistonShopperCommunity StarterCommunity StarterMay 3, 2026permalink
Agree — and I'd add this: Move a coil or plug on the 2024 Rivian R1S if it's cylinder-specific and see whether the code follows. Save the big job until that test fails. Keep sale price, fees, and rate as three different conversations. Only after sitting overnight so far.
BoostGuy47Community StarterCommunity StarterMay 2, 2026permalink
Intermittent stuff lies if you only catch it once. If a shop can't duplicate it on the 2024 Rivian R1S, bring a video plus freeze-frame data, not just a story. That's the branch I'd chase this week. On “brake fluid is old but still looks,” that was the fork that mattered for me. I'd want a dollar figure or a measured spec, not 'should be fine.' If your situation is the opposite, ignore me. I keep a notes app thread for this now.
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