Last weekend, when out on a drive, after half an hour on the motorway, my engine had not got above 70deg, and I was feeling rather cold in the car due to not a lot of heat from the heater. When some work was done to the car a few months back, the thermostat and thermostat housing was replaced (with pattern parts, first one appeared to not work properly leading to a bit of overheating, so this was replaced). I took it back to the garage as I suspected the thermostat to have failed, as when starting the car from cold, and leaving it to idle, the top and bottom pipes of the radiator got warm at the same time. Leaving the car to idle, without driving did allow the temperature to increase to approaching the normal 90, but one I moved off, this dropped, and with some of the weather we have had over the last few days it got down to nearly 50.

Had it in the garage and they have replaced the thermostat with a genuine Skoda one, however, the problem still persists, though it would appear not to quite the same extent. The car seems to warm up faster, and can get up to 90 when driving slowly in traffic, but any sort of speed and the temp drops again back to 70 or below, although this could be due to it being warmer than it was earlier in the week, making it seem different.

I have the car booked in on Wednesday to be looked at further, but is there anything I could have missed here, as the chances of replacing a thermostat with another one that is not working in exactly the same way seems a bit odd to me.

The car has the 1.6 BFQ Petrol engine with the MAP-contorlled thermostat - could there be some other sensor somewhere that is affecting the ECU and making it heat the thermostat prematurely? Coolant temp readings appear to correlate between the dash display and readings using VCDS/Torque?

It is all puzzling me a bit, as what looked like an obvious problem of a broken thermostat is being a bit of a pain!

My vrs is like this although it still gets warm in the cabin. Would be interested to hear if you manage to solve it before I get chance to have mine in at the garage

My VRS did this as well but a genuine thermostat sorted it, I don't know much about the 1.6 but you can test the thermostat (out of the car) using hot and cold water

Fit a genuine stat, & make sure there are no air locks.

My vrs is like this although it still gets warm in the cabin. Would be interested to hear if you manage to solve it before I get chance to have mine in at the garage

2 things usually.

Coolant temp sensor

More likely your thermostat. Not too bad a job to fit, awkward more than anything. Get a genuine VW one.

Start the car from cold check the rad as it heats up. If the stat is working as it should the rad should stay cold then get very hot all over quickly, if the thermostat isn't working the rad will slowly heat up from the start.

Yes, the radiator gets warm gradually as the temperature rises, so points at the thermostat not working, but it was a new genuine skoda one that was only fitted yesterday. Is there a high chance of a dodgy one, or have I just been unlucky? Could it be the ecu doing silly things? Thinking of disconnecting the wires to the thermostat and seeing what happens then.

Is it possible to remove the thermostat without having to drain the coolant?

Pretty sure there are no air locks, as coolant is circulating, and if there were I would have thought over not under heating would be the issue.

Well, the car was back to the garage this week, and is now sorted.

It turned out to be something with the car forcing the thermostat to open (map-controlled thermostat). After the garage reset something using their diagnostics kit, the car is now functioning as it should.

map controlled stat?

can anybody explain this a bit more? I'd like to understand a bit more as have same issue with engine staying cold

tia

This is from my understanding of it, and from what has been happening with my car.

At some points, particularly under a high load I think, the engine operates better at a slightly lower temperature (so the thermostat is controlled by the engine map). The thermostat has a connection to it so that the ECU can at times open the thermostat (by applying 12v across a resistor I guess) that heats up the wax in the thermostat, hence opening the thermostat and allowing the coolant to flow through the radiator, reducing the temp if the engine. With mine, apparently it was doing this permanently, so the car was not getting up to temperature.

I guess one thing that you could try is disconnecting the wires to the thermostat, and then taking a drive and seeing if the car then heats up. Would probably need to do this from cold, as otherwise the wax in the thermostat would have been heated for a while, and would probably stay open for a while longer.