Noticed yesterday that the fans aren't coming on when my torque app says the coolant temps got to 95C. Both fans come on when the aircon or heating are turned on so they physically work. I'm wondering if it's the temperature fan switch? https://partsfinder.bilsteingroup.com/en/article/febi/36563?make=%C5%A0koda&model=Octavia+I+Combi+1996+-+2010&vehicle=1.9+TDI+-+81+kW+%2F+110+hp or is there something else to look at? Fuses all look fine at the battery box.

It's a 2004 1.9 ASV diesel.

Cheers

Vijay

Coolant temperature of 95C at engine won't be hot enough to trigger fan action via the radiator thermoswitch.

The thermoswitch is generally near the outlet of the radiator, so coolant reaching it has already cooled due to passage through the radiator.

The thermoswitch threshold for low speed activity of fans is 95 approx. But that's temperature at the thermoswitch, not at engine (where the sensor you're interrogating lives).

Hi Pete,

That does make sense, thank you. Any idea what the engine coolant temp would need to be to turn on the fan low/high speeds?

Do you by any chance know if VCDS can check the operating temps of the fan switch?

2 hours ago, Vijay2018 said:

Any idea what the engine coolant temp would need to be to turn on the fan low/high speeds?

Will be variable, depending on ambient temps, airflow through rad due to motion, etc.

2 hours ago, Vijay2018 said:

Do you by any chance know if VCDS can check the operating temps of the fan switch?

I don't think VCDS can help you here, no.

At this time of year in UK, with a 1.9 diesel engine, I doubt you'd see fan action due to just radiator temperature very often, if ever.

Why the concern?

2 hours ago, Breezy_Pete said:

Will be variable, depending on ambient temps, airflow through rad due to motion, etc.

I don't think VCDS can help you here, no.

At this time of year in UK, with a 1.9 diesel engine, I doubt you'd see fan action due to just radiator temperature very often, if ever.

Why the concern?

I guess that makes sense with the variable.

I hoped like some other systems you can fool the ecu into thinking the engine temp is hotter.

The concern is my head/head gasket my have gone. I had oil in the water a few months ago and changed the oil cooler. I've been flushing the coolant out over and over but can still see specs of oil. I also get water coming out of the expansion tank. I've changed the cap but water was still coming out.

I monitor my coolant temps using Torque app on my phone. It normally sits 89-92C so I believe my thermostat is working ok(Changed it last year and used a Febi one). But on nearly every journey, I get a spike in the coolant temp where it goes to 97-99C but goes down almost as quick as it spiked.

If your getting coolant coming out of the reservoir its being over pressurised somehow. I would get it checked for exhaust gasses in the reservoir if you cant see any noticeable bubbles. The spike in temp may be an airlock thats caused by exhaust gasses entering the coolant system and then the car is managing to clear air lock. Do your heaters work all the time. Had a HG failure and the first thing was heaters blowing cold

There's bound to be air in the system as I've been flushing it. I know when I did a coolant flush last year it took weeks for the air to come out.

I have had cool air out of the heaters but only now and again and has been linked with low coolant. 99% of the time the heaters work as they should

I do think this is more than just air in the system sadly though..................