2006 Audi A4 B7 2.0T Petrol never gets to normal temperature
Discussion
I have a 2006 Audi A4 Avant with the 200bhp 2.0T engine. I don't drive it that often as I have other cars I prefer, but for practicality and winter, this one comes to the fore. I bought it many years ago for my mother, who probably did no more than 2000 miles a year in it so it has relatively low mileage at about 60k. Anyway, one thing that I've noticed for the past year or so is that it never gets up to temperature except when working extremely hard. The temperature needle will hover around the 70°C mark and then never get above that. Now that it's very cold outside, the needle barely seems to get above 60°C. It used to sit on the middle mark (90°C) when warmed up no matter what the weather. There is no EML or any other indication that anything is wrong, but I am aware that if the engine never gets to temperature, it could cause premature wear.
My first thought is that the thermostat must be stuck open, but a bit of googlage tells me that this is a common problem and that it's often the coolant temperature sensor at fault. If that's the case and the coolant really is getting to the right temperature, then is there any need to worry? I have a multimeter with a temperature probe on a long wire, so I thought I might try to test the coolant temperature using that. If it's normal (around 90°C) then I will try to replace the temperature sensor. If it's low, then I'm guessing I need a new thermostat. I have a Bluetooth OBDII scanner but haven't checked for any stored codes.
Posting here to check if my logic is sound, or whether anyone has any experience with this car/engine and know of other causes of this issue. Thanks!
My first thought is that the thermostat must be stuck open, but a bit of googlage tells me that this is a common problem and that it's often the coolant temperature sensor at fault. If that's the case and the coolant really is getting to the right temperature, then is there any need to worry? I have a multimeter with a temperature probe on a long wire, so I thought I might try to test the coolant temperature using that. If it's normal (around 90°C) then I will try to replace the temperature sensor. If it's low, then I'm guessing I need a new thermostat. I have a Bluetooth OBDII scanner but haven't checked for any stored codes.
Posting here to check if my logic is sound, or whether anyone has any experience with this car/engine and know of other causes of this issue. Thanks!
Because the cold outside temps have dropped the recorded temp, my guess would be on the thermostat.
An easy way to tell is usually to just leave it idling for a while and see if it gets up to normal temp, then afterwards, drive it around 60mph, if the drive causes the temp to drop, it’s likely the thermostat.
An easy way to tell is usually to just leave it idling for a while and see if it gets up to normal temp, then afterwards, drive it around 60mph, if the drive causes the temp to drop, it’s likely the thermostat.
If you can, measure the actual temperature to see whether you have a problem. If you do, the symptoms exactly match a leaking stat. You can sometimes get this sort of symptom in bitterly cold weather just from wind chill through the engine bay combined with any slight trace of a leak through the stat, but if it's happening routinely that suggests the stat is leaking.
I've got a mk5 Golf GTI with a similar engine in that i purchased in the summer, during those months the coolant temperature would eventually get to 90* on mid 10-15mile journeys. As we got into the colder months when the heaters are being used more it became apparent the engine does indeed take a lot longer to warm up, m happy I have the heated seats option!!
I have a few items to replace all at the same time but in order to deal with my situation I am replacing the cam belt & belt driven water pump, the electric water pump & the thermostat ( which comes as a complete housing) before flushing the coolant system through.
In your situation Id start by plugging a bluetooth obd reader in, connecting to something like Torque Lite and getting the ECU temperature,.
Then start checking the electric water pump(s) as i think dsg cars have 2 , checking the coolant hose temperatures into/out of the radiator+ termostat. With the engine running from cold, leave the expansion bottle lid off and check that the coolant return pipe (the smallest of the pipes feeding into the top of the bottle) is flowing coolant back into the tank. If it's intermittent or irregular flow then you could have a water pump issue developing.
I have a few items to replace all at the same time but in order to deal with my situation I am replacing the cam belt & belt driven water pump, the electric water pump & the thermostat ( which comes as a complete housing) before flushing the coolant system through.
In your situation Id start by plugging a bluetooth obd reader in, connecting to something like Torque Lite and getting the ECU temperature,.
Then start checking the electric water pump(s) as i think dsg cars have 2 , checking the coolant hose temperatures into/out of the radiator+ termostat. With the engine running from cold, leave the expansion bottle lid off and check that the coolant return pipe (the smallest of the pipes feeding into the top of the bottle) is flowing coolant back into the tank. If it's intermittent or irregular flow then you could have a water pump issue developing.
If there was a water pump issue the temp gauge would show a higher temp than normal as the engine would be overheating.
Go for a twenty minute drive, so the engine is warm. Ignore the gauge.
Stop, but leave the engine idling.
If the needle on the gauge slowly moves to 90, it’s definitely the thermostat stuck open.
When you drive again, the needle will fall again.
If you drive it hard and fast, the needle could well go to 90 again.
Go for a twenty minute drive, so the engine is warm. Ignore the gauge.
Stop, but leave the engine idling.
If the needle on the gauge slowly moves to 90, it’s definitely the thermostat stuck open.
When you drive again, the needle will fall again.
If you drive it hard and fast, the needle could well go to 90 again.
Start the car from cold & monitor the temp of the hoses as it warms up.
If the stat is working correctly then the engine hoses will heat up quickly & the hoses on the side of the stat that controls the flow to/from the radiator should stay cold but suddenly get hot as the stat opens allowing hot coolant to flow into the radiator.
Some stats are in the bottom hose, but the hose from the rad to the stat should stay cold until it opens & the top of the radiator will stay cool.
If it all warms up gradually then the stat is either defective or missing - the latter being a ploy by the unscrupulous to sell a car that has an overheating problem.
You don't need any fancy equipment, your hands will do fine - just be aware of rotating pulleys, fans & belts etc!
I've had several stats fail over the years & your symptoms are classic.
If the stat is working correctly then the engine hoses will heat up quickly & the hoses on the side of the stat that controls the flow to/from the radiator should stay cold but suddenly get hot as the stat opens allowing hot coolant to flow into the radiator.
Some stats are in the bottom hose, but the hose from the rad to the stat should stay cold until it opens & the top of the radiator will stay cool.
If it all warms up gradually then the stat is either defective or missing - the latter being a ploy by the unscrupulous to sell a car that has an overheating problem.
You don't need any fancy equipment, your hands will do fine - just be aware of rotating pulleys, fans & belts etc!
I've had several stats fail over the years & your symptoms are classic.
Edited by paintman on Saturday 17th December 12:45
Marc p said:
Because the cold outside temps have dropped the recorded temp, my guess would be on the thermostat.
An easy way to tell is usually to just leave it idling for a while and see if it gets up to normal temp, then afterwards, drive it around 60mph, if the drive causes the temp to drop, it’s likely the thermostat.
Yes, it does get a bit warmer if you let it idle, and then cools immediately when you start driving. I haven't tried idling for a long time as that's not typically how I drive and I don't sit in traffic much. But for the purposes of testing, why not. I imagine the radiator fan will kick in once the coolant reaches 90°C?An easy way to tell is usually to just leave it idling for a while and see if it gets up to normal temp, then afterwards, drive it around 60mph, if the drive causes the temp to drop, it’s likely the thermostat.
aka_kerrly said:
In your situation Id start by plugging a bluetooth obd reader in, connecting to something like Torque Lite and getting the ECU temperature,.
Then start checking the electric water pump(s) as i think dsg cars have 2 , checking the coolant hose temperatures into/out of the radiator+ termostat. With the engine running from cold, leave the expansion bottle lid off and check that the coolant return pipe (the smallest of the pipes feeding into the top of the bottle) is flowing coolant back into the tank. If it's intermittent or irregular flow then you could have a water pump issue developing.
I didn't bother with the OBD scanner to check temperature, as surely that's where the dashboard gauge is getting its data? I wouldn't expect the dash gauge to read any different than the OBD scanner does.Then start checking the electric water pump(s) as i think dsg cars have 2 , checking the coolant hose temperatures into/out of the radiator+ termostat. With the engine running from cold, leave the expansion bottle lid off and check that the coolant return pipe (the smallest of the pipes feeding into the top of the bottle) is flowing coolant back into the tank. If it's intermittent or irregular flow then you could have a water pump issue developing.
I'm also pretty sure there isn't a water pump issue - if there were I'd have insufficient cooling which would cause an overheating condition surely!
LunarOne said:
Yes, it does get a bit warmer if you let it idle, and then cools immediately when you start driving. I haven't tried idling for a long time as that's not typically how I drive and I don't sit in traffic much. But for the purposes of testing, why not. I imagine the radiator fan will kick in once the coolant reaches 90°C?
If that's the set temperature of the sensor. Note that that sensor may not be the one that operates the temp gauge.I have had gauge sensors fail, but they've either not registered at all or they've gone off the hot end of the gauge - which is a bit of a brown trouser moment!
Edited by paintman on Saturday 17th December 13:26
Tony1963 said:
If there was a water pump issue the temp gauge would show a higher temp than normal as the engine would be overheating.
Go for a twenty minute drive, so the engine is warm. Ignore the gauge.
Stop, but leave the engine idling.
If the needle on the gauge slowly moves to 90, it’s definitely the thermostat stuck open.
When you drive again, the needle will fall again.
If you drive it hard and fast, the needle could well go to 90 again.
As above, I shall try that too. I'm not looking forward to replacing the thermostat (which I'm 95% sure is the culprit) on this car as it's apparently not the easiest of jobs. Especially when it's so cold!Go for a twenty minute drive, so the engine is warm. Ignore the gauge.
Stop, but leave the engine idling.
If the needle on the gauge slowly moves to 90, it’s definitely the thermostat stuck open.
When you drive again, the needle will fall again.
If you drive it hard and fast, the needle could well go to 90 again.
paintman said:
Start the car from cold & monitor the temp of the hoses as it warms up.
If the stat is working correctly then the engine hoses will heat up quickly & the hoses on the side of the stat that controls the flow to/from the radiator should stay cold but suddenly get hot as the stat opens allowing hot coolant to flow into the radiator.
Some stats are in the bottom hose, but the hose from the rad to the stat should stay cold until it opens & the top of the radiator will stay cool.
If it all warms up gradually then the stat is either defective or missing - the latter being a ploy by the unscrupulous to sell a car that has an overheating problem.
I'll definitely try that out and I can see that it makes sense. Thanks!If the stat is working correctly then the engine hoses will heat up quickly & the hoses on the side of the stat that controls the flow to/from the radiator should stay cold but suddenly get hot as the stat opens allowing hot coolant to flow into the radiator.
Some stats are in the bottom hose, but the hose from the rad to the stat should stay cold until it opens & the top of the radiator will stay cool.
If it all warms up gradually then the stat is either defective or missing - the latter being a ploy by the unscrupulous to sell a car that has an overheating problem.
LunarOne said:
aka_kerrly said:
In your situation Id start by plugging a bluetooth obd reader in, connecting to something like Torque Lite and getting the ECU temperature,.
Then start checking the electric water pump(s) as i think dsg cars have 2 , checking the coolant hose temperatures into/out of the radiator+ termostat. With the engine running from cold, leave the expansion bottle lid off and check that the coolant return pipe (the smallest of the pipes feeding into the top of the bottle) is flowing coolant back into the tank. If it's intermittent or irregular flow then you could have a water pump issue developing.
I didn't bother with the OBD scanner to check temperature, as surely that's where the dashboard gauge is getting its data? I wouldn't expect the dash gauge to read any different than the OBD scanner does.Then start checking the electric water pump(s) as i think dsg cars have 2 , checking the coolant hose temperatures into/out of the radiator+ termostat. With the engine running from cold, leave the expansion bottle lid off and check that the coolant return pipe (the smallest of the pipes feeding into the top of the bottle) is flowing coolant back into the tank. If it's intermittent or irregular flow then you could have a water pump issue developing.
You gauge will likely read what looks like 90 degrees anywhere between 80 & 100 degrees, and the areas aside of that are also a bit dead so that pretty much anywhere between 70 & 110 looks in a relatively normal range.
Don't quote me on those numbers but you get the idea.
I went out this evening for a 20-minute drive, and by the time I got to my destination, the inside of the car was nice and warm and all the windows were completely clear of frost, but the temperature gauge was reading about 65°C. As I was in a supermarket car park, I let the car idle and the temperature gauge needle moved very slowly, taking about 15 minutes to get to 90°C. I waited a further 15 minutes and tried raising the revs to 2000 in an attempt to get the temperature above 90, but no go. After picking up a few items I got back to the car and the gauge was now reading about 85, but the minute I started the car and coolant started circulating, the temperature plummeted straight down to 70. And once I started driving home, it dropped further, to what I estimate was about 60°C.
When I got home, I took a temperature reading from the coolant in the little expansion tank to find that it reads 62.5°C. So the temperature gauge in the dash is spot on and it's not the sensor.
Question: If the thermostat is not working, why won't the temperature go above 90°C? Is it possible for the thermostat to partially work in such a way that it still varies the amount of coolant going through the radiator, but can't fully shut the radiator out of the coolant loop? I never heard the radiator fan come on, but I don't know whether it would be loud enough to hear. My two other cars with electric fans make a fairly loud noise when it comes on.
When I got home, I took a temperature reading from the coolant in the little expansion tank to find that it reads 62.5°C. So the temperature gauge in the dash is spot on and it's not the sensor.
Question: If the thermostat is not working, why won't the temperature go above 90°C? Is it possible for the thermostat to partially work in such a way that it still varies the amount of coolant going through the radiator, but can't fully shut the radiator out of the coolant loop? I never heard the radiator fan come on, but I don't know whether it would be loud enough to hear. My two other cars with electric fans make a fairly loud noise when it comes on.
My Vito van heater was a bit poor the other day, so I flicked through the dash settings until I found the engine temperature setting. The engine temp fluctuated a bit, depending on driving conditions, but never got above seventy degrees. Obviously I thought the thermostat was borked, so I popped the bonnet. The header tank was warm to the touch, but the top hose was stone cold, so the thermostat was obviously still shut.
Turned off the heater on the way home, and the temperature made it up to eighty, and that was after going up Pool Bank. Top hose still cold.
Turned off the heater on the way home, and the temperature made it up to eighty, and that was after going up Pool Bank. Top hose still cold.
LunarOne said:
...........Question: If the thermostat is not working, why won't the temperature go above 90°C? Is it possible for the thermostat to partially work in such a way that it still varies the amount of coolant going through the radiator, but can't fully shut the radiator out of the coolant loop?
Because the radiator is functioning correctly connected to the low ambient temps, the cooling system is working but the coolant temp is maintained by the stat.Watch the "warm up" curve left.
Maxdecel said:
Because the radiator is functioning correctly connected to the low ambient temps, the cooling system is working but the coolant temp is maintained by the stat.
Watch the "warm up" curve left.
Thanks for that. So the thermostat is still working, but it's just not sealing properly any more even when cold.Watch the "warm up" curve left.
I've found a video detailing how to change the thermostat on my engine. Looks like if I heed warnings of not trying to use Torx bits, I'm going to need a triple-square/spline drive set to do it. I don't need more than as hint of an excuse to buy more tools!
https://www.youtube.com/watch?v=ixyRYG44lfs
LunarOne said:
Thanks for that. So the thermostat is still working, but it's just not sealing properly any more even when cold.
I very much doubt it, MBG ? It'll be stuck open (failsafe) Also I would expect an extended warm up usually noticed this time year by a cool heater for a much longer period.LunarOne said:
Maxdecel said:
I very much doubt it, MBG ? It'll be stuck open (failsafe) Also I would expect an extended warm up usually noticed this time year by a cool heater for a much longer period.
MBG?Speed watched the Vid & Pt. 2 VAG Stuff doesn't change, hoping for a shot of the stat
Typically they've made a special unique housing.
A correctly working stat will keep opening & closing to allow greater or lesser quantities of coolant to flow to the radiator to maintain the engine at correct working temperature which will be determined by the stat.
If you look at most stats they will have a temperature stamped on them.
It isn't a case of once the engine has warmed up it opens & stays open.
When you sat idling there is no airflow through the rad as the car isn't moving & the temp will go up.
As soon as you started driving again you had airflow over the radiator which cooled the coolant down again. Faulty/no stat results in overcooling which I think is what you are experiencing.
You may also experience an increase fuel consumption as the ecu will see the engine as being cold & increase fuelling accordingly.
If you look at most stats they will have a temperature stamped on them.
It isn't a case of once the engine has warmed up it opens & stays open.
When you sat idling there is no airflow through the rad as the car isn't moving & the temp will go up.
As soon as you started driving again you had airflow over the radiator which cooled the coolant down again. Faulty/no stat results in overcooling which I think is what you are experiencing.
You may also experience an increase fuel consumption as the ecu will see the engine as being cold & increase fuelling accordingly.
Thanks everyone! I've ordered a spline drive bit set and will order a genuine Audi thermostat either tomorrow or Monday, depending when they are open. Looks fairly easy to do - it's just under the alternator. I think it'll take me an hour or two to do assuming I can get all the hoses off cleanly.
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