Johngerard

The power required towing at 57MPH whether on the level or on a slight incline will be exactly the same whether the car is 150BHP or 190BHP, surely it doesn't require remotely like 150BHP at this relatively moderate speed?

These lovely comfort temperature gauges for more than 20 years now will read a rock steady 90C between 75C and 107C, your coolant might actually be up around 105C so worth checking it with a scan tool both with and without the towing load in case its something as simple as a thermostat.

Just came across this on some VCDS website... IDE00025 Coolant temperature 85 °C IDE00192 Coolant temperature at radiator outlet: actual value 55.2 °C IDE00194 Coolant temperature at radiator output: specified value 90.0 °C ENG105382 Coolant temperature 85 °C ENG106503 Coolant temperature at radiator outlet 85 °C

You're right re the 2.25C but the stat should still operate normally?. I'd like to know what this 95.3C "radiator output specified value coolant temperature" refers to, is it the (a) actual radiator outlet coolant temperature.

I looked at that VCDS incorrectly, the rad coolant outlet was apparently 225C, 95.3C might be the temperature which starts the radiator cooling fan, but if the coolant was 225C then the equivalent (saturation) pressure is > 25bar but the cooling system PRV lifts at ~ 1.5bar so don't know what's going on there.

Yes, and no, a faulty sensor will have no effect on the stat's opening temperature, but one would think that the coolant display should have stayed "permanently" below 50C as I presume it uses the same sensor. If those VCDS readings were taken with the engine idling then the 95.3C Rad outlet doesn't tell a awful lot because the stat, even if working perfectly, will normally (eventually) go full open while idling and the radiator fan will cut in/out. Replacing that sensor will tell alot if VCDS still available to you.

That's a very low oil pressure, don't know what it should be in the mid/high rpm range but would expect at least 50/60 psi, needs investigating.

I had a January 2000 Bora (manufactured in mid 1999) whic had one pressure switch + the inhibit up to ~ 1600 RPM.

Looks very like that IMO, what does the pressure fall to at say 1800/2000 RPM?

Yes, of course, the oil pressure is higher at higher revs, because of this due to higher specific power outputs the alarm has to be annunciated at a higher oil pressure and because of this and the (money saving) necessity of having to install two pressure switches then the "fix" was to disable the alarm until ~ 1600 RPM.

Strange how the new stat is aparently "open" with cold/cool engine coolant temperature. The (any) stat shouldn't begin to open at say 84C ish and go fully open at ~ 98C. All Vag cars will display 90C between a true coolant temperature of ~ 75C and ~ 107C so your displayed temp should reach 90C well before the stat starts opening/top hose getting hot, you can see my 2019 Polo just reaches a displayed temperature of 90C when the true temperature only reaches 75C, if yours only reaches a displayed 70C, ~ 63C true temperature even while driving then it would appear that this new stat is also passing (even though one would think unlikely) or else installed incorrectly, if this is possible. VW Polo 02092024 Coolant Temp VCDS/Car Display 52 /52 53/55 56/58 58/62 60/65 63/69 64/72 66/74 68/78 69/82 71/84 73/86 74/88 75/89 75/90

If @klobb still has the old stat, see (if you can) if its partially open, if not, put it in a pot and see what temperature it begins to open, should be ~ 84/88C

No sure about very modern VAG cars but for at least 25 years, the oil pressure alarm isn't enabed until the engine revs are > than ~ 1600rpm, (previous to this there were 2 oil pressure switches fitted). If you have a genuine low oil pressure than it will cease to annunciate once the revs drop below this ~ 1600.

Maybe a compression test in order?, it may, (hopefully not), be a sticking inlet valve.

08:17:35 Oct 2025. Jan 2019 Polo with original 59AH EFB battery Engine Off October 2025 IDE01834 Battery voltage 12.256 V IDE01836 Battery current -4.407 A IDE01837 Temperature of battery sensor 15 °C IDE01839 Battery charge level 78 % IDE01841 Battery internal resistance 7.4 mOhm IDE01842 Usable battery charge 27 Ah IDE01948 Battery internal resistance not normed 6.8 mOhm IDE07681-MAS06086 Battery total charging throughput-Total re-charge 3480.7 Ah IDE07681-MAS06087 Battery total charging throughput-Entire energy throughput 3671.1 Ah November 2025 Ultimate Speed 5A charger with voltmeter. Model ULGD 5.0 C1 Battery came from 70% SOC with following smart charger input charger 13.3V @ 1653 charger 13.5V @ 1800 4 Bars indication charger 14.4V @ 1945 4 bars indication Voltage then fell to 13.5V with a trickle charge of ~ 0.8A, charger then disconnected, VCDS then showed 84% SOC but don't know if I had left the charger "trickling away" for hours on end if the SOC would have risen to 100%. The usable battery charge was/is allegedy 27AH so lots of starts hopefully left at ~ 0.25AH/start.

Even though I only use the Stop/Start selectively, I allways test it my enabling it (Stop) every time I exit the car and even with a battery SOC as low as 70% (VCDS) will still operate perfectly. The battery, a 59AH EFB, is the original and is exactly 7 years old. I returned very recently from abroad, the car had been idle for 11/12 days but Stop/Start operated perfectly after travelling the mandatory 0.5kms.

Diagnostics is a big money maker for Main Dealers, even if the car is under warranty I believe you may have to pay for this?, Victim: "My windscreen wipers are noisy", "Yes Sir, our diagnostics does confirm this, that will be £150 Sir, £60 for the new wipers and only £90 for the diagnostics." Sharp Brakes??, For those of us old enough to remember it, what about the brake limiting/proportional valve, or whatever it was called, before the days of ABS?

Yes, on my 2019 (petrol) Polo, you may have to press/release the brake pedal a few times before the engine restarts, obviously when the vacuums falls to some minimum level. Engine coolant temperature has no effect whatsoever on mine, the OAT (& engine) temperature can be as low as -2C, once you drive the car its mandatory exactly 0.5kms, the engine will stop if the stop/start is enabled, its disabled if the OAT falls to -2/-2.5C, can't rememer which just now.

Stalls while idling or driving or both? Crankcase "breather" valve faulty? There might be plastic piping that sometimes crack and are almost invisible but these generally cause a fast idle. ( I think you've covered that, above) Can you attach a vacuum gauge somewhere on the inlet manifold.?

Any update re the above?., did you get the stat to open??.

Actually, that little plastic tank is a Degasser, even with the stat shut, you should see a small flow of water entering this tank, remove the cover and watch it.

I wouldn't be 100% happy until you do that test above (let the heater off), one would have thought that if you have/had driven it after installing this stat and because the top hose was apparently air locked that you should get overheating again, I've changed the coolant in a few cars of your era and I used to just let the cover off the header tank until the coolant was good and hot, sometimes, after a drain down and a cold engine, only 1/2 the coolant could be added but as soon as the stat opened then the remainder could be poured in.

Very good, what you might do now sometime is to drive the car normally and ensure the diagnostics see a temperature of at least 86/88C, the stat opening temp, it goes fully open a ~ 98C so would expect around 90/93C (actual temp) under normal driving conditions, it might rise to the stat opening value while idling but may not at these low ambient temperatures now.

Overall, the discs+drums on mine gives excellent braking and doesn't seem to be quite as sensitive at very low speeds as others experience, however I can truly say that it wins first prize for the worst hand brake I've encountered in 63 years of (VW) driving.

Can you ensure, with a vernier calipers or whatever that the 2 replacement stats are dimensionally the same as the the original failed shut one.