I will be telling the garage to do the DSG cooler fix when they open today as I've been doing some observation over the weekend for a different issue (oil sensor workshop! / intermittent signal) after the garage changed the oil cooler due to coolant leak. 

 

If I'm being honest, I noticed something weird about the temperatures 2 winters ago, and I flagged it up then, but they didn't think it was anything to worry about, vaguely something about it's cold outside. I've been been feeling sick all weekend for not having basically ordered them to do the fix years ago and have been driving around all this time with basically no thermostat. I rely on this car basically to keep myself and my animals alive. 

 

Basically oil temperature driving around town this weekend was 62C after 1 hour with engine on, or 72C if I turned off AC. Motorway was 85C max. The coolant never reached 90C. It stayed 78 when the car was stationary and dropped to 68 on the motorway. 

 

The thing is though, I remember even just from 3-4 months ago, when it was warmer, I was doing a DPF regen at 2.5k revs and oil temp went over 100C on the motorway as high as 108.

 

It's more obvious with a Carista dongle (which I only bought a couple of months ago) to see temperatures. It showed DSG mostly at 55C. 65 max. Also, the carista apps shows an exact coolant temperature, the needle might look close to 90 on the dashboard, but it's only 70 something, it's just not accurately presented at all. 

 

Anyways. What are the likely damage caused that I should keep an eye on for the future? And how much life has been taken off the engine? After doing some research online, apparently some cars will throw an check engine light if the engine doesn't get up to temp within a certain time. Skoda really missed a trick by not throwing an engine light when a thermostat is broken. 

Edited 9 September, 20241 yr by newskodadriver

Ah, the joys of having your concerns brushed aside until they become actual problems—always a great feeling. It's amazing how a vague "it’s cold outside" explanation was supposed to put your mind at ease back then. But hindsight, as they say, is 20/20. At least now you’ve got your Carista dongle confirming what you’ve been suspecting all along.
 

As for the fluctuating temperatures, it’s definitely not ideal. I can see why you'd be uneasy, especially given how much you rely on the car. The oil and coolant temps you’ve been observing do seem a bit off, and it’s unfortunate that the car didn’t flag the thermostat issue earlier—certainly would've saved some headaches.
 

In terms of long-term damage, it’s tricky to say exactly. Running the engine at lower-than-optimal temperatures could lead to increased wear over time, but hopefully catching it now will prevent any serious issues down the road. It’s good you're getting the DSG cooler fix sorted too, and hopefully the garage takes your concerns seriously this time.
 

It’s frustrating when you feel like you should’ve pushed harder earlier, but you’re taking the right steps now, and that's what matters. Fingers crossed everything goes smoothly from here on out!

Hello, assuming this is a diesel, your engine could have suffered significant damage and excess wear if it has been running significantly under temperature for over two years. How many annual miles do you run? How frequently has the engine oil been changed? How often is it currently running a DPF regen?

3 hours ago, Winston_Woof said:

Ah, the joys of having your concerns brushed aside until they become actual problems—always a great feeling. It's amazing how a vague "it’s cold outside" explanation was supposed to put your mind at ease back then. But hindsight, as they say, is 20/20. At least now you’ve got your Carista dongle confirming what you’ve been suspecting all along.
 

As for the fluctuating temperatures, it’s definitely not ideal. I can see why you'd be uneasy, especially given how much you rely on the car. The oil and coolant temps you’ve been observing do seem a bit off, and it’s unfortunate that the car didn’t flag the thermostat issue earlier—certainly would've saved some headaches.
 

In terms of long-term damage, it’s tricky to say exactly. Running the engine at lower-than-optimal temperatures could lead to increased wear over time, but hopefully catching it now will prevent any serious issues down the road. It’s good you're getting the DSG cooler fix sorted too, and hopefully the garage takes your concerns seriously this time.
 

It’s frustrating when you feel like you should’ve pushed harder earlier, but you’re taking the right steps now, and that's what matters. Fingers crossed everything goes smoothly from here on out!

Car is on 315k now, had a compression test before last winter at 270k and pressure was 26psi across all 4 cylinders. 

 

If wear was "twice as much", then I would expect 70k less life. Dunno if how that's supposed to work. 

 

It's coming off as a taxi next year, but even then I'm not going to sell it. I'm rather attached to it. It won't be worth trying to sell a 350k mile car, people might turn their noses up at it, and most of things will be "new". For example, by the end of this year, every single suspension component will have been replaced within a 12 month period, and it had new clutch pack and flywheel done last Xmas. 

 

Yeah the explanation wasn't the best back then. But also, I never focused on oil temperatures all the way through out. I would check if it was heating up from - - -, and I might check it on the motorway during a regen, but not during driving about town. The fact that the car doesn't have a coolant temperature readout or DSG fluid temperature without an advanced OBD dongle and the needle not very accurate and no CEL also didn't help. 

 

I rang the the garage this morning and they're going to sort it this week. 

3 hours ago, Warrior193 said:

Hello, assuming this is a diesel, your engine could have suffered significant damage and excess wear if it has been running significantly under temperature for over two years. How many annual miles do you run? How frequently has the engine oil been changed? How often is it currently running a DPF regen?

35-40k miles a yesr, so as per title, I assume a distance of 70k driven with faulty thermostat. 

 

No oil sludge or excess condensation was ever noticed at servicing. Every 9000-9400 miles. 

 

When not during winter, for example 4 months ago in May, the oil temperature could reach 100C, so I assume moisture / contaminants will have been burnt out at irregular intervals when weather was not cold. 

 

Currently with an ash value of 0.32, every 200 miles for DPF regen. 

 

Garage also doesn't think any damage would have been caused at all. Dunno how true that is. It certainly can't be great for the engine, and even if oil viscosity matter more for protection than oil temperature, it will have put more pressure on the pumps for the engine and the DSG unit. 

Edited 9 September, 20241 yr by newskodadriver

8 hours ago, newskodadriver said:

the needle might look close to 90 on the dashboard, but it's only 70 something, it's just not accurately presented at all. 

 

That has been the case with all VAG vehicles for 25 years now.

 

8 hours ago, newskodadriver said:

Skoda really missed a trick by not throwing an engine light when a thermostat is broken. 

 

You dont need a check light to tell you that the engine is not warming up to operating temperature, your toes under the heater duct will tell you that.

 

As you do such a high mileage and presumably work full shifts I doubt your engine will have suffered any extra wear, certainly nothing that could be measured or even detected by oil analysis through operating at lets say 20°c below optimum temperature, it will have suffered far less wear, many magnitudes less than most vehicles whch are driven less than 5 miles each urban journey.

 

 

2 hours ago, newskodadriver said:

Car is on 315k now, had a compression test before last winter at 270k and pressure was 26psi across all 4 cylinders. 

 

If wear was "twice as much", then I would expect 70k less life. Dunno if how that's supposed to work. 

 

It's coming off as a taxi next year, but even then I'm not going to sell it. I'm rather attached to it. It won't be worth trying to sell a 350k mile car, people might turn their noses up at it, and most of things will be "new". For example, by the end of this year, every single suspension component will have been replaced within a 12 month period, and it had new clutch pack and flywheel done last Xmas. 

 

Yeah the explanation wasn't the best back then. But also, I never focused on oil temperatures all the way through out. I would check if it was heating up from - - -, and I might check it on the motorway during a regen, but not during driving about town. The fact that the car doesn't have a coolant temperature readout or DSG fluid temperature without an advanced OBD dongle and the needle not very accurate and no CEL also didn't help. 

 

I rang the the garage this morning and they're going to sort it this week. 

Is the 26 psi you quote the maximum difference across all cylinders?

4 hours ago, J.R. said:

 

That has been the case with all VAG vehicles for 25 years now.

 

 

You dont need a check light to tell you that the engine is not warming up to operating temperature, your toes under the heater duct will tell you that.

 

As you do such a high mileage and presumably work full shifts I doubt your engine will have suffered any extra wear, certainly nothing that could be measured or even detected by oil analysis through operating at lets say 20°c below optimum temperature, it will have suffered far less wear, many magnitudes less than most vehicles whch are driven less than 5 miles each urban journey.

 

 

Ah that's a little disappointing to hear about how inaccurate needles are on VAG cars. Through extensive Googling over the weekend, I found that on newer Audis, you can display the coolant, engine oil, and dsg oil temperature side by side in numerical C on the dash display. Would have made it far more obvious. On my car, it took digging through carista reader options to find them all. 

 

This is only the second car I've owned. I've driven approximately 280k miles since I got my drivers license. 258k of those have been in this car. Frankly, I don't ever want to part with it even if it will no longer be used a taxi next year. 

 

About the heater thing. The thing is, there was always heat in the winter, car was warmer than the house as I live alone and heating the rented 3 bed semi with single glazing and heating system that's 60 years old far too expensive. I might have been insensitive to how quickly it blew hot from one winter to the next, but I was always eventually warm. Again through Googling, apparently a thermostat problem would be more obvious if the driver was cold in winter, which I wasn't. 

 

I don't always work a "full shift", but the mileage is there. I never use it to just "pop to the shops". My commute from town to city includes 3 miles of dual carriageway near the start and end of every trip. Where I go for my shopping, I have the options of 6 miles through urban / semi urban roads, or 12 miles on dual carriageway and motorways, I choose the motorway option 90% of the times because I like driving in a straight line without start / stopping or changing gears. 

 

Hopefully as you say any damage in my case will have been more limited. When I drive at gear changing boundaries, since 150k miles ago, I always manually lock the dsg in the lower gear at 1.5k revs rather than let the dsg go to the next gear at 1.2k. And it was you who told me about the nifty gadget to help with EGR, that should have also made my engine combust at higher temperatures. 

Edited 9 September, 20241 yr by newskodadriver

Taxi driving is probably the kindest thing one can do to these diesel engines, my chauffeur pal put 188K miles on the MK1 Octavia he sold me after 3 years, I took it on to 325K miles and it still sounded like a sewing machine despite all the abuse and neglect it suffered in my hands.

 

Pleased to hear you invested in the EGR device, its reassuring to be (fairly) confident that it is not going to go pop and give me a major job to do, its a real work up on a 4x4.

16 hours ago, J.R. said:

Taxi driving is probably the kindest thing one can do to these diesel engines, my chauffeur pal put 188K miles on the MK1 Octavia he sold me after 3 years, I took it on to 325K miles and it still sounded like a sewing machine despite all the abuse and neglect it suffered in my hands.

 

Pleased to hear you invested in the EGR device, its reassuring to be (fairly) confident that it is not going to go pop and give me a major job to do, its a real work up on a 4x4.

So, I have some questions about how the thermostat and the coolant system actually works. 

 

So according to what I've read, a thermostat is sort of blocking device that unblocks when a block of wax reaches 75C in the case of the DSG thermostat and triggers a spring to open. 

 

So I'm assuming whenever the DSG thermostat reaches 75C, regardless of whatever the actual DSG transmission oil temperature reading is, as the thermostat is a mechanical device, not an electrical one. And upon reaching 75C, it forces the entire coolant system to move to the radiator, cooling the coolant, which is then circulated through both the engine oil cooler and the dsg oil cooler. 

 

So my questions are. If the coolant temperature is 75C, then it would be as if there was no DSG thermostat. So how does the coolant actually reach 90C and stay 90C if nothing was broken? 

 

Also, is the main thermostat also set to 75C? 

 

And, since I had to replace the engine oil cooler recently because the plastic casing cracked. Is the DSG oil cooler also plastic and should I replace it out of caution at the next DSG oil change (due in several thousand miles anyway for me) 

 

Also, now in my 3rd day of intensively looking at temperature readings on Carista, my oil temperature this morning in a 90 minute drive reached 82 in urban conditions and stayed at 79 mostly. So I dunno why the same 90 minute block on Saturday night only resulted in an engine oil of 65C. It does seem like once engine oil reaches 80, it will stay around 79-82C. So the overcooling might not have been as catastrophically lower as I'd imagined. 

 

The garage said they don't have time to do it this week, and I'm making a 150 mile trip twice on Saturday for a personal event, so I'll be interested to see if will reach high 90s on sustained motorway driving at 2.2k revs. 

Sorry for the delay, I took a break from the forum.

 

The thermostat is not an on-off device that triggers a spring, it operates gradually and linearly over a relatively wide temperature range.

 

The thermostat is held shut (no coolant flow) by the spring, the spring is opposed by the force exerted from the wax capsule which expands with temperature.

 

As the engine warms up the thermostat gradually opens allowing coolant flow, as the temperature continues to rise it will become fully open by the rated temperature, say 88°c, in a healthy cooling system that will only happen in extremis, towing up a hill in hot weather etc, normally the orifice will be partially open to maintain the regulated 88°c.

 

There is actually some coolant flow when closed, there will be a metering hole with a jiggle pin to stop it becoming blocked, that way the warming coolant can reach and pass over the wax element, if this flow does not happen the engine will initially overheat before the thermostat opens through conduction of its metal body and then the temperature will fall before being maintained at the 88°c.

On 16/09/2024 at 11:43, J.R. said:

Sorry for the delay, I took a break from the forum.

 

The thermostat is not an on-off device that triggers a spring, it operates gradually and linearly over a relatively wide temperature range.

 

The thermostat is held shut (no coolant flow) by the spring, the spring is opposed by the force exerted from the wax capsule which expands with temperature.

 

As the engine warms up the thermostat gradually opens allowing coolant flow, as the temperature continues to rise it will become fully open by the rated temperature, say 88°c, in a healthy cooling system that will only happen in extremis, towing up a hill in hot weather etc, normally the orifice will be partially open to maintain the regulated 88°c.

 

There is actually some coolant flow when closed, there will be a metering hole with a jiggle pin to stop it becoming blocked, that way the warming coolant can reach and pass over the wax element, if this flow does not happen the engine will initially overheat before the thermostat opens through conduction of its metal body and then the temperature will fall before being maintained at the 88°c.

Fixed yesterday, dsg thermostat + new filter pipe + labor = 90 pounds. 

 

All temps back to normal. 84 coolant, 85 dsg oil, 90 engine in town and 95 on motorway. 

 

The dsg takes a bit longer now to reach 55C, as previously the engine would warm the coolant instantly which would warm the dsg instantly, but now can maintain higher normal temperatures. Engine now warms much faster. 

 

I think fuel economy is also up a bit, not like massively, but every bit helps. 

Edited 18 September, 20241 yr by newskodadriver

Glad to hear that at least one garage somewhere is not ripping the ar5e out of their customers!

9 hours ago, J.R. said:

Glad to hear that at least one garage somewhere is not ripping the ar5e out of their customers!

They're a pretty reputable VAG specialist, but even if they weren't, garages generally don't try and rip off taxi drivers, who tend to be good customers if treat well. 

Although I've found garages that do a lot of expensive Audis tend to be more "carefree" with their pricing.. 

I replaced both my thermostats at home. Easy work, and I just replaced the dsg thermostat since a Febi Bilstein one is rather cheap. Then I know that car is properly done. Engine coolant now stays steady at approx 90C and dsg temp around 85-90C as well. Oil temps around 90-120C depends on load etc. Also heat in cabin works as supposed to.