Engine not reaching or holding operating temperature – 2.0 TDI CFGB

Hey everyone,

I’m having issues getting my engine to reach and hold proper operating temperature. It warms up very slowly and often drops back down when driving, especially downhill

Here’s what has been done so far:

• New main thermostat (OEM spec)

• New DSG thermostat

• EGR cooler delete

• EGR delete (software + hardware)

• New timing belt kit

• New Continental water pump

• System has been vacuum-bled and refilled using proper filling equipment

Car: Škoda Superb 2014, 2.0 TDI (engine code CFGB)

Despite all this, the car still won’t stay at full operating temperature — it hovers around 70–75 °C, only briefly touching 90 °C before dropping again.

Any ideas what else could cause this? Could there be something with coolant routing, the secondary loop, or a bypass issue?

Thanks in advance!

Could it be because of EGR cooler delete, or did you have issues before this as well? I would think that the EGR gases would increase the coolant temp.

the issue was the same as before the EGR delete.

Is new thermostat working? It can be faulty.

Have you readed temp by obd or gauge? Coolant hoses arent hot either?

yes, the new and old T-stat both work, visiual confirmation, read with OBD scanner, the cars gets heat from the climate control and all hoses are hot but its just not gaining oparating temp.

If hoses are hot are you sure that coolant temp sensor is working?

Yes pretty sure, the oil temp follows the coolant temp about 10 degrees more than the coolant temp which is normal

Engine oil is a coolant, and the coolant is to bring the oil temperature down to nearer than that 10*oC or more difference.

Is the Anti Freeze / Summer coolant / rust inhibitor AKA the coolant at the correct ratio / strength for your use / ambient temps?

There is a reason some use Radiator Blinds / Screens in cold weather conditions. To speed up the heating of the coolant / engine / engine oil & to keep an efficient oil temperature.

Edited 13 November, 202513 Nov by Evolution13

Yes, im using 50/50 pemco 912+

I had a front wheel drive superb 2013 model. 2.0tdi CFGB 170hp version. Driven 311.000km. The temp gauge did not behave like this. This is not normal behaviour for this engine.

20 hours ago, franko02 said:

Yes pretty sure, the oil temp follows the coolant temp about 10 degrees more than the coolant temp which is normal

Think i'd still be wanting a validation check of that the coolant temperature sensor is working though. There's not much else to change and not having 100% confidence in the sensor wouldn't sit right with me.

Thermostats are pretty basic pieces of equipment so if that's working, nothing else should really be effecting operating temp.

Have you noted at what temperature the radiator fan starts and what method are you using to validate the temp.

Does the heater blow Hot not just warm. If the heater blows hot and doesn't cool down as it blows it is most likely the sensor.

You could also invest in one of these for your toolbox

Edited 14 November, 202514 Nov by Stonekeeper

Ive noticed that what comes temps at engine bay, infared meter is not accurate. Rubber hoses usually give less heat.

But if you measure vents and how how air you get in cabin its okay.

If all is fine my temps has been +82c at middle vents when outside was -25. Car fully warm and on highway.

Now my mahle/behr thermostat is weak and 80->87c lasts very long. Usually temp stalls when 70c is reached.

Why is an infra re meter pointed at the engine block not accurate?

If you get a consistant 82 from the vents it's the dashboard gauge that is wrong so that points to the temp sensor

Edited 15 November, 202515 Nov by Stonekeeper

Maybe it shows iron/cast block temp better but ive never got accurate readings from hoses. Allways 10-20c less than coolant inside.

2 minutes ago, Karpov said:

Maybe it shows iron/cast block temp better but ive never got accurate readings from hoses. Always 10-20c less than coolant inside.

I agree if you point it at the hose the reading will be less than the reading of the actual coolant inside. But how do you verify that the reading you are relying on for the temp inside is correct?

Using the reading from the hose see what temp is reached for the radiator fan to kick in. If the thermostat is new and the hose gets to above 75 before the fan kicks in, if the heater blows at 82 and remains at 82 when the fan kicks in. The temperature gauge or temperature sensor are the ones that are wrong because you know the coolant is definitely higher than 70-75 which is the temperature you say the car hovers around?

The heater cannot blow hotter than the coolant temp can it, it must be cooler

5 hours ago, Karpov said:

Ive noticed that what comes temps at engine bay, infared meter is not accurate. Rubber hoses usually give less heat.

But if you measure vents and how how air you get in cabin its okay.

If all is fine my temps has been +82c at middle vents when outside was -25. Car fully warm and on highway.

Now my mahle/behr thermostat is weak and 80->87c lasts very long. Usually temp stalls when 70c is reached.

Agree that rubber will not give an accurate reading, but there will be accessible metal parts that will give reasonably accurate ones.

Sorry my language. I just meaned that 82c is temp inside when all ok (thermostat working and engine coolant heat 87-89c.

I think coolant fan kicks out 95c or higher? I remember that older vag's had combined sensor for temp and fan, four wire model. If there is same kind at 2.0tdi then fan is not working either. But maybe there is own for fan.

I think for topic starter easiest way is just install new temp sensor and look what happens.

34 minutes ago, Karpov said:

Sorry my language. I just meaned that 82c is temp inside when all ok (thermostat working and engine coolant heat 87-89c.

I think coolant fan kicks out 95c or higher? I remember that older vag's had combined sensor for temp and fan, four wire model. If there is same kind at 2.0tdi then fan is not working either. But maybe there is own for fan.

I think for topic starter easiest way is just install new temp sensor and look what happens.

Sorry I didn't realise you were not the OP, they just keep coming on looking and not responding. So we are wasting our time.

No worries! I just try to write in english and give some advice at backside

Little update. Changed the reservoir cap, also changed a hose that has 2 “check valves” inside, nothing changed. I have oem coolant heat sensors and a oem resorvoir. Plan is to change that 1 thing at a time to try and isolate the issue. Also got a hotter mhale T-stat wich is rated for 92 degrees. Just to note the problem seemed to come when the timing belt kit was put in. Continetal. But i did not drive the car long enough to get a good measurement on that becuse the oem timing belt was in the car at 181.000km so i drove the car very little prior to the timing belt change. Anyone had any issues with the continental water pumps on these engines?

Do you have mahle installed? I have mahle too and its that crap what isnt working anymore.

I dont about this car's water pumps but back in the days some alternative pumps had poor blades and coolant flowed bad -> too much heat.

I dont think that pump can be too powerful which can cool too much engine if we are talking original type pumps not racing etc.

It has a continental timing belt kit including the pump. Myle T-stat 87 degres, the mhale is the supplyer for VAG so its oem. Next step is puttint the hotter 92 degrees mhale T-stat

Update. Unplugged the auxiliary water pump and the car reached operating temp. I went looking in live data and the temperature for the egr cooler says -270 degrees. I would relly like to know what the temperature is on other egr coolers according to the live data reading.

Hi mate, did you ever fix this issue? I’m having same problem

Not yet, changed the small auxilary water pump, didnt make a difference