With this colder weather I have noticed that the car is taking slightly longer to get to temperature when in town and if you turn the window demist blower on the coolant temp gauge shows a drop in temperature.

 

The drop in temperature with the demist blower occurs wether in town or on the motorway.

 

When running at motorway pace tenoertaure seems fine.

 

My initial thought is that the thermostat is stuck open, however I’ve been thinking again and is what I am seeing as a result of having the egr blanked off this summer and now as a result of now warm air being in the egr it’s not aiding the temperature.

 

Does anybody else have the same issue, with or without egr or is it definitely the thermostat??

 

**edit: car is a 2010 2.0 CR TDi VRS

 

Thanks

Edited 2 December, 20178 yr by Quiksilver_TR

How old is it?

2 minutes ago, SuperbTWM said:

How old is it?

 

Yes, that info would help

alot wouldn’t it.

 

its a 2010 2.0 CR TDi VRS

I would change the thermostat going by the age, they start to open early as they get old and a new genuine or other quality part will give you the best chance.

 

If its still the same after you change it then its just down to you pulling too much heat from the engine. Personally, If I want to clear the windscreen, I do it manually and lower the fan speed a bit instead of using the demist setting , especially since you normally want to use it at the start of a journey when the engine is still cold.

 

 

Edited 2 December, 20178 yr by SuperbTWM

9 minutes ago, SuperbTWM said:

I would change the thermostat going by the age, they start to open early as they get old and a new genuine or other quality part will give you the best chance.

 

If its still the same after you change it then its just down to you pulling too much heat from the engine. Personally, If I want to clear the windscreen, I do it manually and lower the fan speed a bit instead of using the demist setting , especially since you normally want to use it at the start of a journey when the engine is still cold.

 

 

 

Yeah, I’ve already got a new thermostat here for it but was hoping it wasn’t the cause as it looks like a real ball ache to do due to it being hidden under the egr valve/throttle body and behind the alternator.

48 minutes ago, Quiksilver_TR said:

 

Yeah, I’ve already got a new thermostat here for it but was hoping it wasn’t the cause as it looks like a real ball ache to do due to it being hidden under the egr valve/throttle body and behind the alternator.

 

If you have VCDS or a scan tool with live data you could go for a drive, with minimum heat, and see what the temperature tops out at before going to the trouble of changing the stat.

 

Of course your EGR mod won't of helped as you have mentioned

6 minutes ago, SuperbTWM said:

 

If you have VCDS or a scan tool with live data you could go for a drive, with minimum heat, and see what the temperature tops out at before going to the trouble of changing the stat.

 

Of course your EGR mod won't of helped as you have mentioned

 

 

Yeah, my scan tool does do live data so that’s worth a look.

 

Need to find the measuring block number for the coolant temp.

May not exactly the same problem, but I’ve found there is a second thermostatic valve on my Scout with DSG. It’s just at the side of the of the gearbox oil cooler. I noticed that on some journeys (even lengthy motorway runs)  either it could take 45 minutes to get up to temp or the temp wouldn’t stay at 90, but would drop to 70 or lower at times. Discussed with the dealer who said that they didn’t come across may main thermostat failures and it was booked at 3+ hours labour, so I was keen to try cheaper options first! Anyway a look on a ver VW forums identified a similar issue and identified this second valve as a possible issue. Further on the thread just turned into a load of replies saying they have tried this and it fixed the issue. It’s worth while saying there was nothing coming up on VCDS.

 

So today I swapped mine over. Took about 40 mins to do, but I wasn’t rushing things. Took it for a quick run afterwards and in 10 minutes it was up to temp. The gauge came up nice and smooth with none of the dropping back to 70. I’ll only know if it’s been the fix over the next couple of weeks, but so far seems like £23 was worth it!

On 12/3/2017 at 23:59, uncle bulgaria said:

 

So today I swapped mine over. Took about 40 mins to do, but I wasn’t rushing things. Took it for a quick run afterwards and in 10 minutes it was up to temp. The gauge came up nice and smooth with none of the dropping back to 70. I’ll only know if it’s been the fix over the next couple of weeks, but so far seems like £23 was worth it!

How's going so far, noticed any difference after change? 

Edited 7 December, 20178 yr by Bushas

I'm being cautious in this response, but so far it seems to be running consistently at 90c, however only a lot more miles will truly show if it has fully resolved the issue. This is the part.

Hi guys

Thanks to all who have posted as without you I would never have solved my coolant problem.

As with others my car over a period of 6 months was failing to reach full operating temp in colder weather and if it did as soon as I would begin to coast the temp would begin to fall. I will add that as with others the car would take quite a long time to reach the correct temp even from new. My vehicle is a skoda octavia 2litre diesel dsg, same as vw. Now as with others I replaced the main thermostat at great cost and no result.

I have had the same experience in Aus as well, nobody knows about this part at VW so I ordered the part to be told there are only 2 in Australia. I guess that if the dealers don’t know about the part there is no demand.

Now here is the very strange part of my experience. I replaced the part and it works perfectly, after 3km at 10 degrees the car is at full operating temp. The strange bit is that on inspection of the old part there was no thermostat inside the plastic enclosure.  Same part number exactly. So I looked more closely and removed the clip that holds the two ends together. No sign of a thermostat in the plastic enclosure. Very very strange but the problem has been fixed.

Would be interested if anyone else has come across this.

Hi Tezza01,

 

I thought your finding was extraordinary. Aftet all those years, you get to a point where you feel you have a problem - presumably it got cold there and then you find that a critical part attached to the gearbox cooling (I guess that's what it is isn't it?) doesn't have any components inside. That's amazing. I have an Octavia mk2 FL 2.0 TDI VRS and it seems to be having an issue. I drive on the motorway and the heat comes up OK, within say about 6-8 miles - I can hear the heat coming first because it makes the plastic vents expand and they make a small noise when they do - and I could drive hundreds of miles and everything is fine, until I slow down to come into town. The heat rapidly goes away and by the time I am sat at the first set of traffic lights my heater has turned into a rapid icer.

 

I have read up on this extensively and whilst many people report same or similar its important to try to attach more than one symptom in order to identify the cause. People say it could be an old thermostat opening too early or stuck open. Others suggest it might be a spinning rotor on the water pump - these are the plastic rotors known to either break up or spin on their shaft. Whilst I think both of these are possibilities I have to work through the cheapest possibilities first. The reason I think my problem may be a water pump issue is that at about 1800 rpm my heat comes back, if its a constant rpm. That may be because the rotor starts to spin up and whilst the rpm is maintained it eventually 'catches up' with the water flow and keeps it moving. I guess if the rotor had completely failed I would overheat.

 

For now I am aiming at thermostat but given there are two and one is really quite a pain to get to, I feel inclined to do what you did. Its not such an expensive fix. It may be the solution. But as another poster pointed out, a thermostat (referring to the main - normal thermostat) that's nine years old might well be opening early. They are meant to fail in the open position. When one looks at the construction of a thermostat its amazing that such a poorly made thing can do its job for so long. The plastic one in a pip looks like it might be better.

 

Would be great if you posted an update on your situation. Was your problem solved permanently without having to replace the main thermostat?

 

Take care - stay safe.

 

Look at this study...

 

https://youtu.be/WZSKoNGTR6Q

 

Ric N

I heard interesting comment from VW indie workshop on this problem. The reason for it is that the thermostat part inside the housing detaches & breaks up. The pieces of it go into the gearbox where they’re chewed up and destroyed. Sometimes it causes a problem but most often it is without long term effect apart from the fact you notice the heating issue. Most likely before you noticed that, you experienced perhaps a crunch or other disturbing sound from the gearbox; sometimes a strong resistance can be felt briefly as the thermostat parts get forced into & through rotating masses. As the thermostat is a lot softer than the gearbox parts, the gearbox wins. The initial problem with this is thought to be a defect in the material joining the thermostat to its housing. 

" I heard interesting comment from VW indie workshop on this problem "

 

I'd make sure I didn't use this Indie Workshop for any servicing etc.

 

The thermostat is in the cooling system.

If it does break up, & I'd be surprised if it did, the bits would be contained within the cooling system.

They can't get into the gearbox.

 

If you've got a DSG gearbox, your problem will almost certainly be the DSG cooler thermostat that is stuck open.

Reduces the heater output & gives increased fuel consumption from the cooler running engine.

On 27/05/2020 at 12:45, PipH said:

" I heard interesting comment from VW indie workshop on this problem "

 

I'd make sure I didn't use this Indie Workshop for any servicing etc.

 

The thermostat is in the cooling system.

If it does break up, & I'd be surprised if it did, the bits would be contained within the cooling system.

They can't get into the gearbox.

 

If you've got a DSG gearbox, your problem will almost certainly be the DSG cooler thermostat that is stuck open.

Reduces the heater output & gives increased fuel consumption from the cooler running engine.

I did think it was an extraordinary thing to happen. I envisioned plastic & tin plate being crunched through cogs and landing in the gearbox oil filter. Perhaps it was the DSG thermostat the workshop was referring to.

 

Your comment about DSG cooler thermostat making the engine run cooler if it’s stuck, I looked on my car after hauling the air box out and snapping the drain pipe in the process! that there isn’t a thermostat on my gearbox anywhere near the cooler. I’m a bit puzzled here; isn’t the DSG cooled by an oil cooler? I see a finned block with pipes going to the gearbox but no devices inline. How would heater water be affected by DSG temperature? I don’t get it! As these cars have got quite complex, I wouldn’t be surprised if the bonnet open/closed position switch controls the oil level warning sensor. Nothing would be surprising any more after I have read some. They are certainly ‘clever’ cars and I like the VRS a lot, but diagnosing things can be tricky, even if one has codes to refer to.

Have a look at this diagram :-

https://skoda.7zap.com/en/cz/octavia/oct/2010-663/1/121-121053/

 

Part No 88 is the gear oil cooler. ( Gearbox oil to coolant heat exchanger )

 

It connects via pipework to part No 15 ( bottom right ) which is the gear oil cooler thermostat.

 

But i'm only guessing at your engine code, check that first.

Hi guys, i'm having this exact problem on my '09 octavia vrs limited edition 2.0tdi... although, i have a manual gearbox. 

My problem started once the temperature sensor on the passenger side of the engine popped out of its housing. I replaced the sensor and the housing with TPS parts and also i've replaced the front thermostat and the parking pump 'B'. I still havent managed to correct my lack of temperature issue. 

 

When ordering a new thermostat from euro carparts, they said there was 2 thermostats listed for my car... the front thermostat, hidden behind the alternator... and also a thermostat in its own housing... although from reading 100+ threads on coolant issues, it seems that '2nd' thermostat only exsist's on DSG models? Although i'm not 100% sure i'm correct. 

 

Could somebody please enlighten me if the cr170 manual has 2 thermostats, or if its only the DSG model which has 2?

 

Thank you!