Coolant Light Comes On Without Reason

[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?

[Paula&Marcus]

Hi,

Just replace the "Engine Overheat Tell Tale Relay" and maybe also the "Radiator Fans Control Relay" and the "RPM Relay"

If this does not help, there is also a "Low Coolant Level Module" which might be faulty.

BTW, the past MY94 "Revised Harness" cars have a way different logic that works without relays !

Cheers

Marcus

Edited January 6, 2009 by USAndretti42
Removed quote of immediately-preceding post

[sanj]

I believe disconnecting the level indicators will make the light come on, try grounding them instead. I have found them to be somewhat iffy, so clean the contacts. There is also a ground contact on the header tank, very easy to overlook.

There are several sources for the coolant light:

1) The temp sender to the ECU under the intake tells the ECU the temperature you see in FreeScan, if it exceeds the threshold the ECU sets the light via the engine overheat relay.

2) The chargecooler level sensor in the header tank via the cc low coolant level module.

3) The engine coolant level sensor in the header tank via the engine low coolant level module

Edited January 6, 2009 by USAndretti42
Deleted unnecessary quote

[Techspy]

I should have explained that I did ground the level wires on the header tanks, not just disconnect them. The temps seen in freescan are exactly what the gauge is showing....86 when hot and the light on.

I guess I will go ahead and start changing the relays.

Thanks for the info guys.

[rene1993earlys4turbo]

Hi my friend try changing the heather tanks pressure plugs