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So guys my Polo 6r with engine cbzb 77kw is misbehaving.

I have an obdii gauge and also the Carly obdii dongle both monitor the coolant temperature.

After 20 minutes driving with 20⁰c outside the coolant temperature rises to 102⁰c momentarily and then drops to 96⁰c. This cycle continues during the drive.

I have noticed that the rad fan comes on at 102⁰c for a few seconds only at the low speed and the temperature drops to 96⁰c.

The rad fan runs when the AC is on.

Before this begun the car would run steady at 96⁰c according to the obdii gauge.

I had the thermostat replaced yesterday and the problem persists. The water pump was replaced around 5000 miles ago.

When does the rad fan kick on?

Any imput much appreciated.

It seems like normal behaviour of the cooling system within the appropriate parameters.

Thank you for the reply.

I worry that this temperature levels are too high and I believed that the radiator fan would come on at it's low speed at 96c.

The coolant temperatures at which the fan turns on and off are appropriate, and it is also normal for the fan to run when the A/C is turned on.
The outside temperatures and the power/load required are determining factors 'for the times' in which the fan is working, which is not a cause for concern.
It is certain that the thermostat is working correctly, another thing is that the replaced pump is performing adequately or providing the correct flow.

Install a new pump if you think it is not working properly.
Use original spare parts on this occasion if you did not do so in the previous pump replacement.

Thanks for your reply my friend. I will be keeping an eye on the coolant temperature with the OBD2 gauge and if it starts creeping upwards I will change the pump.

As a precatory measure, you can use your hands/take a look -with the engine cold- to check the vacuum lines or electrical connectors to ensure that the engine control unit or cooling system components are receiving the correct signals. Use a flashlight.

No worries to have, a +100°C water temps is normal.

Thank you for your insights guys.

I tend to overthink things at times

I had the same "issue" when trouble shooting my engine hesition when cold.
I was thinking about a bad temp sensor.

When I saw 106+ degrees I felt so bad. But after few research, it's perfectly normal.

Le_Combattant wrote: Tue Nov 12, 2024 2:54 pm I had the same "issue" when trouble shooting my engine hesition when cold.
I was thinking about a bad temp sensor.

When I saw 106+ degrees I felt so bad. But after few research, it's perfectly normal.

So what ended up being your problem and solution for the slaggish jerky hesitation ?

This, carbon on the intake ports:

Le_Combattant wrote: Sun Dec 01, 2024 2:20 pm This, carbon on the intake ports:

PXL_20240228_125632473.jpg

Thanx! How did you end up cleaning it ?
Soda blasting (or similar) in a workshop ? or did you do anything yourself ?

Retali wrote: Thu Dec 05, 2024 9:45 am

Le_Combattant wrote: Sun Dec 01, 2024 2:20 pm This, carbon on the intake ports:

PXL_20240228_125632473.jpg

Thanx! How did you end up cleaning it ?
Soda blasting (or similar) in a workshop ? or did you do anything yourself ?

Ice blasting, company service (250 euros).