Coolant warning lamp

[nicknameless]

05 Fabia VRS

Last weekend early morning (3-4 degrees C) the coolant warning lamp came up on start up. Let it run for a while and warm up a bit and when restarted it didn't come back again. Coolant level above the min. Put it down to the cold snap.

This morning exactly the same, drove to work and thought the lamp would go out. About 5 mins into the drive the temp gauge rose much quicker than it would normally do. Reached 90 and didn't overheat. Stopped car and restarted and again the warning lamp does not come back on. Coolant level above min.

Any ideas? Will top coolant up slightly this eve but the relatively rapid rising needle, which I haven't seen before got me thinking there is something wrong here.

Many thanks.

[Ootohere]

Do not over top up your coolant.

If you are sure you have good antfreeze in to the correct ratio, then leave it alone and do not tamper.

(Has it been checked or even changed recenty, as in the last few years.)

Your engine starts and the thermostat is closed,

the coolant circulates around the engine untill around 81 degrees celsius coolant temperature, then the thermostat opens and the coolant circulates around the whole system.

Thats is how it should work, & sounds like yours is doing as it should do..

So if you have the correct Antifreeze ratio, no leaks nothing that is wrong,

watch the cold mornings and see how it goes.

Do not go opening Pressure caps & looking for problems that are not there.

Do not go topping up something that has a good level.

If below minimum, it needs topped up.

JMO obviously.

george

[nicknameless]

Thanks a lot for that.

I would guess the car has not had a coolant change. I haven't changed it in the 18 months I've owned it and no record in the history either.

The weird thing this a.m. was the rapid rise on the temp dial, which I have not seen happen before, hence my concern.

[nicknameless]

any chance this could be the expansion tank? reading old threads this seems to be a culprit often.

[GWS]

I have very similar symptoms on my 2004 octavia combi. 1. The coolant shortage indicator lamp, (is this the same lamp as over heating indicator?) goes on and stays on when started in winter temperatures. Will not go out by it self but if I restart the car after running a few minutes, it remains off. Coolant level ok. 2. Also the temperature gauge is intermittent. It may appear to rapidly come up to 90 but it is only because it suddenly starts to function. When driving it mostly works correctly but does also drop off to the cold position only to come back up after a bit. The shortage lamp always remains off after restart.

 

I am suspicious of the sender and or the plug. It does not want to click into position but seems to sit in position. I have wiggled the plug while the temp gauge was not working but had no affect.  I am not sure if these things are related. Could both of these anomalies be a faulty sender unit or a poor connection at the plug?

 

Realize I am coming late to this topic but I just bought this car a few weeks ago. Any light on this subject would be great.

[ChrisWerrett]

I'm getting the same but I have a faulty temperature sensor in the engine so putting it down to that. the original ones are known for giving false readings according to the chap who does my diagnostics and remapping..  might be worth plugging it in to see if any fault codes come up..

[GWS]

I will replace the sender and start there.