coolant light is making me crazy

[techspy]

I am getting a coolant light (not the washer light) after driving awhile. here is what I have checked.

1. Disconnected both level indicators (chargecooler and normal header tank). Still comes on, not a coolant level issue.
2. Opened front radiator top plug to ensure no air pocket.
3. Removed thermostat and tested in hot water, opens and closes as it should. Its an 82c thermostat.
4. Confirmed in Freescan that it is not overheating and is not throwing any codes.
5. All fans are ok, not setting off engine check light like a faulty fan would.

There is no overflowing coolant, all temps are well within specs and has never gotten over 90 even with a/c on idling in traffic for a long time in hot weather.

My only other thought is that the relay is bad relay and is setting it off. The only thing is that it only comes on until after driving awhile. I would think that this would still show a code though. It will go off after driving at a higher speed after awhile (Not really fast, IE 45mph, more airflow?). Is it possible the sensor for this light is different than the gauge? Maybe it is getting heated from ambient engine temps? I am stumped.

Any ideas?

[bob-in-toon]

I had exactly the same problem when I had the Esprit - the coolant light starting coming on once the engine had warmed up so I checked the top up reservoir in the rear 'boot' and it was full as was the case when I looked in the engine bay filler.

I took it to a Lotus specialist in Newcastle who basically said the same as you, that it was probably an electrical issue, faulty sensor etc. However whilst mine starting going off only once the car had been driving a while it sometimes started lighting up the moment I switched the engine on. Then a period of about 4-5 weeks went by and there wasn't a problem, then it came back on again. On the plus side its not something that will damage the car, you just need to keep a good eye on the coolant in the meantime as you obviously can't rely on the car to tell you


I never actually got around to sorting it out but have you tried looking at the fuses to see if any of them deal with the coolant measuring? I'm not that mechanically minded so I might be speaking rubbish! However ive had the same issue so I know its irritating!

Regards

Bob

[JK1]

TS,

There are two coolant temp sensors,one for the dash gauge and one in the water jacket of the intake manifold under the plenum for the ECU. Sounds like you have a problem with the second one. It could be a flaky sensor or bad connection or wiring.

On your car with two header tanks there are also 2 cylindrical low coolant modules in the engine bay relay box one or both of which may be the source of your problem. Check the wiring at the pins for those modules as well as the relay for the manifold sensor.

So to recap, the areas that can cause the low coolant light to come on:
2 header tank level sensors
2 coolant level modules
coolant temp sensor in intake manifold and associated relay

Let us know when you find the problem.

[LotusSE89]

techspy said:

I am getting a coolant light (not the washer light) after driving awhile. here is what I have checked.

1. Disconnected both level indicators (chargecooler and normal header tank). Still comes on, not a coolant level issue.
2. Opened front radiator top plug to ensure no air pocket.
3. Removed thermostat and tested in hot water, opens and closes as it should. Its an 82c thermostat.
4. Confirmed in Freescan that it is not overheating and is not throwing any codes.
5. All fans are ok, not setting off engine check light like a faulty fan would.

There is no overflowing coolant, all temps are well within specs and has never gotten over 90 even with a/c on idling in traffic for a long time in hot weather.

My only other thought is that the relay is bad relay and is setting it off. The only thing is that it only comes on until after driving awhile. I would think that this would still show a code though. It will go off after driving at a higher speed after awhile (Not really fast, IE 45mph, more airflow?). Is it possible the sensor for this light is different than the gauge? Maybe it is getting heated from ambient engine temps? I am stumped.

Any ideas?

The coolant level sensors at the bottom of the tank cannot be removed without causing the light to come on... by opening the circuit you are doing the same that a low coolant level would do, which is to turn on the warning lamp.

Is your coolant level ok? Are both systems topped up all the way? Does the light go off? (wires must both be connected)

Do the wires have a good crimp connection?

The wire to the temp sensor to the thermostat can also work loose, did you check that?

You should also keep the overflow bottle in the boot filled up half way.

[techspy]

I should have been more specific. I disconnected and grounded the header tanks wires. Yep, all levels are toped off and the overflow tank is at half. I will double check the connection to the sensor under the manifold. I can see if the connection was loose that the expansion caused by heat from the engine may affect it. I will then start replacing relays I guess.

Thanks for the info guys.