Hi i've got an octavia 1.9tdi 2000 'x' with a climatronic heating and cooling system fitted, last week it started overheating for no apparent reason. Though 2weeks previously i did get the aircon regassed at my local skoda dealer. Since the overhaeting started i've driven around with the heating on to keep the engine stable . Over the weekend i replaced the thermostat,2 attempts as i fitted it wrong the first time . Aircon works fine, but temp gauge still rises if you press on or the air con is running , as soon as you stop the fan brings the temp down really quick. I'm now getting no heat ,but having read some of the other posts am gonna check heater matrix for airlock. Think ther's probably airlocks in other parts of system also. any thoughts or advice appreciated up until this car has been faultless.

When you switch on the aircon, are both fans running?

When you switch on the aircon, are both fans running?

larger fan runs ,and smaller one does cut in when it gets really hot .aircon cools fine,but flushed heater matrix yesterday but still no heat. Checked old thermostat and its opening and closing,so going to swap that with the new one thats in block now.going to flush rad and block today. temp gauge stays stable in the middle for about 5miles after start up,then goes upinto red,. whether heating or aircon is on or not. temp soon drops if your stationery at lights,etc. even when the gauge is pegged in the red the car not losing water or steaming,the hoses are all tight. As its 'climatronic ' thinking of getting it on a diagnostic to see if anything faulty,any ideas or thoughts gladly received.

Water pump failure?

When the aircon is on both fans should run, iirc.

Also there is a slight possibility the CTS could have failed too (but that won't explain the lack of heat through the matrix)

Water pump failure?

When the aircon is on both fans should run, iirc.

Also there is a slight possibility the CTS could have failed too (but that won't explain the lack of heat through the matrix)

Had heat through matrix before i put the new thermostat in,excuse my ignorance ,whats the 'cts',and is there anyway to check the water pump without ripping the cambelt covers off,can i just run the car to see if its pumping when i'm changing the stat?

CTS = coolant temp sensor. It has 2 feeds, one to the dash gauge and one to the ECU. The older ones are black, and modern ones green. They are quite a common failure, but may not be related in this case.

You haven't lost any gaskets for your thermostat into the cooling system during the change?

As for testing the water pump, I am not sure, it is at the bottom of the block. What happens is that sometimes the impella breaks up, or simply detaches from the shaft, so the shaft spins but the impella does not.

I would wonder if the pump had failed and you had an air lock, reasons being:

- temp drops when driving - pump not working

- no heat from matrix - air lock

To check the water pump, remove the cap to the coolant reservoir and check that coolant is returning to the reservoir via the small pipe. If you raise the engine RPM to about 2500 you should get a steady stream.

To check the water pump, remove the cap to the coolant reservoir and check that coolant is returning to the reservoir via the small pipe. If you raise the engine RPM to about 2500 you should get a steady stream.

That's a great tip.

That's a great tip.

temp goes up when driving,goes down if your stationary just idling which makes me think pump may b ok as it must b pumping water through rad as the temp drops pretty rapidly with the fans going. think waterpump is kaput as no water returning to expansion tank and squeezing hoses just pushes the water round system,can't feel the hoses pressurising ,so gonna replace pump,thanks for all the suggestions and advice,trevor

Edited 13 July, 201114 yr by rhi