Cooling SystemQuestionCommunity Starter

1998 Lexus LS — temperature climbs in traffic but drops once moving

DealHauler287Community StarterMay 11, 20261998 Lexus LS 400Portland

1998 Lexus LS 400, about 79,000 miles. Coolant temperature rises while sitting with the A/C on, then drops once the car is moving. Coolant level looks correct. Fans run, but I do not know whether they are reaching full commanded speed. I am in Portland.

5 replies

RoadScout307Community StarterCommunity StarterMay 11, 2026permalink

I wouldn't throw parts yet. Loaded-suspension checks on the 1998 Lexus LS catch play that a wheels-hanging inspection misses. Don't erase codes until someone who can help has seen them. Run the total, not the monthly, before you commit. Checking again after work.

SunBeltHunter540Community StarterCommunity StarterMay 11, 2026permalink

I'd want a measurement, not a hunch. Two 1998 Lexus LSs can feel identical and have different causes, so measure before you copy someone else's repair. If the cheap test changes it, stop and reassess. This is from a 1998 Lexus LS in Portland with 79,000 miles. Had a similar mess a couple years ago and that's what finally sorted it. Video is ugly but it shows the hesitation.

BatteryDriverCommunity StarterCommunity StarterMay 11, 2026permalink

This is usually cheaper to test than to guess. Two 1998 Lexus LSs can feel identical and have different causes, so measure before you copy someone else's repair. If the cheap test changes it, stop and reassess. This is from a 1998 Lexus LS in Portland with 79,000 miles. I'd want that in writing, not as a promise. Parking it somewhere I can hear it better next time.

SunBeltHunter540Community StarterCommunity StarterMay 11, 2026permalink

Start with the test that can prove you wrong. If a shop can't duplicate it on the 1998 Lexus LS, bring a video plus freeze-frame data, not just a story. If the cheap test changes it, stop and reassess. This is from a 1998 Lexus LS in Portland with 79,000 miles. A shop burned me once by skipping that step. Worth doing even if the car feels fine right now. No warning lights, which is why I'm documenting it.

V8Shopper511Community StarterCommunity StarterMay 12, 2026permalink

Agree — and I'd add this: If a shop can't duplicate it on the 1998 Lexus LS, bring a video plus freeze-frame data, not just a story. Don't erase codes until someone who can help has seen them. On “temperature climbs in traffic but drops once,” that was the fork that mattered for me. Run the total, not the monthly, before you commit. Climate here is different, so treat that as a local data point. Video is ugly but it shows the hesitation.

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