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Flashing temp. light questions

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Car 2001 C2. My temperature light started flashing today while driving in town with the A/C on. The temp gauge had the needle basically between the 8 and 0 on the 180 mark (normal). The ambient temperature was around 89 degrees Fahrenheit with very high humidity. I know the flashing light can mean basically two things...low coolant levels or a fault in engine compartment fan. I have a couple of questions.

1. Does the flashing light throw a code to what is wrong that is stored (i.e. low coolant or fan fault)? If so how long is the code stored?

2. On the coolant expansion tank there is a bleeder valve at the top. It was my understanding that pulling up the clip opened the valve. Is the correct? I was messing around with this when I realized that the black plastic slide (for lack of a better word) that moves up and down on the bleeder assembly (most like the valve) the and is that is attached to the metal clip feels like it has a spring on it. It would seem that pulling the metal clip up would cause this “slide” to go up. However, mine appears to be in the “up” position already. I actually can push down on this and have it move and return to the “up” position. Is this normal operation or has the mechanism failed in the open position.

3. How long does the engine have to cool before you can read the expansion tank?

I suspect the problem is a low coolant matter for a couple of reasons. 1st the engine compartment fan was working yesterday and 2nd I had this flashing light problem when running the A/C after the dealership drained all the coolant out while doing some work last fall (don’t ask). Unfortunately I don’t run the A/C as much as most and this has really been the first time I have run the A/C for an extended period of time in traffic.

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My car is making me a liar. Right after I posted I went out to look at it as it has been about 2.5 hours since I last drove it. The relief valve is no longer stuck in the open position and is instead working the way I thought it was suppose to. The coolant has come back into the tank and is between the Min and Max marks.

Seems like a silly question but can the coolant appear correct in the expansion tank but in fact be low. Maybe from “air” in the system or am I thinking incorrectly? Is the remedy to attempt to add coolant like described in the third radiator DIY?

Edited by bet
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I only have basic information from my experience with the same problem you described.

Temp light flash indicates low coolant condition. It does not throw a code or get stored anywhere.

From my understanding, the sensor is a pressure sensor hence it could be triggered thru a leak within the system or turn itself off as the temp rises and the system has more pressure within it.

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Coolant warning lamp: on when ignition switched on, goes off when engine started. If it comes on steady when engine is running, coolant too hot. If it flashes, coolant level too low.

Cooling system is notoriously difficult to carry out effective bleeding, so yes level could appear correct but still have insufficient liquid in the system. There's two long horizontal pipe runs at the lowest part of the car if you think about it. If the dealer had to drain you system, get them to refill it again. The total (from empty) capacity is about 12 litres.

The 'third radiator' thread is good to explain how to fill the system to capacity.

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  • 4 weeks later...

Another issue that will cause your coolant light to flash is the engine compartment temp sensor. The sensor is held by a rubber grommet and at times will vibrate itself free dropping onto the motor, which is much hotter than the air surrounding it. When this happens your engine compartment fan never seem to turn off and the low coolant temp light will flash even though you are not losing coolant or have a leak. This is because the DME looks at this temp sensor and will turn the low level light on as a default.

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