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My '97 V8 instrument binnacle coolant level warning light keeps coming on. This happens about 30 seconds after a cold start and sometimes straight after starting. The light goes out with the thid or fourth bit of spirited acceleration but comes back on when returning to idle. The tendancy for the light to be on gets progressively less as the car warms up but still sometimes comes on at idle. This has happened for about a year now and in that time, the coolant level has never dropped and is completely normal and where it should be. I have changed the sensor and thouroughly cleaned the contacts of the sensor wires. Sometimes the light flickers on cornering (like it would if the level was right on the edge of the sensor trigger and the lateral acceleration sloshed coolant to the side of the tank causing the sensor to switch on), but I tried putting way too much coolant in and it made no difference to the pattern of light behaviour. The wiring all seems intact and I've rattled the loom around a bit to try and avoid shorts but no change. There is also no change in the light (on or off) if the wiring is jiggled about while the engine is running. There was a time when thumping the top of the coolant tank made the light go out, but this no longer seems to work and if this was a true phenomenon, then the new sensor should have cured it.

I also considered that the coolant may have dropped and then stayed stable but low, but the extra coolant test as detailed above made no difference.

It doesn't bother me that this happens as I know the coolant is OK and aas long as the light goes out at some point, things are likely to be OK. It's just annoying that we can't find the fault....Any suggestions?

By the way, in the last 3 months, the car has had a new battery and a new alternator (no change in bulb behaviour) so I doubt it is a voltage problem.

Thanks :)

Edited by toyroom
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When cold check the level in the coolant tank in the engine bay, probably down a bit, also make sure the overflow tank in the wheel well has the correct amount of coolant. When cold it's drawn into the main coolant tank, and as it warms up(expands) it gets pushed back to the overflow tank.

Add some radiator stop leak, bars leak is a good choice. This will lube the coolant system (pump and seals) and stop minor liner leakage and radiator leaks. I use a bottle per year in my cars.

Bars leak

Likely the problem is the sensor, if your sure the coolant is filled correctly and fine level wise in the main and overflow tanks then replace the sensor.

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  • 2 weeks later...

I would guess that the float level switch is closed when the fluid is above a certain level, so it would fail safe. Confirm that that's the case and then jumper the wires closed. Drive awhile and see what happens. If you still get the problem the intermittent is down stream in the wiring or ECU connector.


The Older I get the Faster I was

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