Temp gauge fluctuations

Modecorp

Modecorp

A2OC Donor
Noticed that it takes my 1.4 petrol around 8 minutes in cold weather to show 85 degrees (never gets to 90). Then it’s fluctuates very slowly back down to 80, then a few minutes more slowly goes towards 90 again, etc etc etc.

Is this normal or should I be looking at replacement temp sensors and thermostats?

I realise it’s not an accurate temp reading, but every other car I’ve ever driven hits 90 degrees and stay at that reading continuously.
 
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Modecorp said:
Noticed that it takes my 1.4 petrol around 8 minutes in cold weather to show 85 degrees (never gets to 90). Then it’s fluctuates very slowly back down to 80, then a few minutes more slowly goes towards 90 again, etc etc etc.

Is this normal or should I be looking at replacement temp sensors and thermostats?

I realise it’s not an accurate temp reading, but every other car I’ve ever driven hits 90 degrees and stay at that reading continuously.
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Sounds like a thermostat needs changing to me
 
Have you got ac? I only ask as when you do there's a nice rad sat infront your coolant rad to lower its efficiency and help keep it's heat once thermo has opened. My tdi this week has taken 15 mins on the motorway to get to 90 especially when using a bit of heat in the car. Rarely at 90 in this weather, my thermostat is tested genuine too. Plus I've flushed whole system 4 times in summer. Only thing I don't have is the undertray.

The moment I come off.motorway and have the heater on it drops again to as low as 65
 
CrispyEdd said:
Have you got ac? I only ask as when you do there's a nice rad sat infront your coolant rad to lower its efficiency and help keep it's heat once thermo has opened. My tdi this week has taken 15 mins on the motorway to get to 90 especially when using a bit of heat in the car. Rarely at 90 in this weather, my thermostat is tested genuine too. Plus I've flushed whole system 4 times in summer. Only thing I don't have is the undertray.

The moment I come off.motorway and have the heater on it drops again to as low as 65
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Yep I have AC too, so that‘s a good shout. Once on the motorway today it sat at 88-ish and then dropped again to 80-82-ish when off on smaller roads. Had the heating on in the car and set for 20 degrees auto all the way home.
 
OK so its worse news if you have ac, I would suspect the thermostat not operating properly as first port of call. Because with ac rad in front your car should hold heat slightly better than non ac.
 
That can be the issue with the climate. You select a temperature that the system attempts to maintain in the cabin. Cold outside air temperatures mean that the system is actually working ( or at least trying ) to supply a significantly higher temperature. Not exact figures by any means but say with a selected temperature of 20 and an outside temperature of 10 then it is feasible the system is running nearer 30 to cope. You then slow down and the engine heat output is greatly reduced hence the gauge drops. Unfortunately it is more a "quirk" of the system than a fault. The thermostat on the diesels starts to open at 87 so any engine temperature below that and is is closing reducing the flow to the radiator. The fixation with their temperature gauge never reading anything other than 90 is to say the least in colder weather totally unrealistic, how much it drops still depends at least partially on the driving conditions.
 
Axit said:
My 1.4 petrol BBY, gets to 90 and sits there, whether I`m moving or not.
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The petrol engines produce enough heat to keep the thermostat open even if the cabin heater is also on full. The diesels are so darned efficient that they can barely heat themselves up when it's cold, let alone the cabin, and certainly not if they aren't under continuous load. This is why the diesels have either an electric element to try to help out with cabin heating or, better, a Webasto pre-heater up to about mid-2002 (2003 model year maybe). The Webasto burns diesel directly to heat the engine coolant, for both the engine and the cabin. A working one is a wonderful thing :)
 
Proghound said:
The petrol engines produce enough heat to keep the thermostat open even if the cabin heater is also on full. The diesels are so darned efficient that they can barely heat themselves up when it's cold, let alone the cabin, and certainly not if they aren't under continuous load. This is why the diesels have either an electric element to try to help out with cabin heating or, better, a Webasto pre-heater up to about mid-2002 (2003 model year maybe). The Webasto burns diesel directly to heat the engine coolant, for both the engine and the cabin. A working one is a wonderful thing :)
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Just outside now planning to mend mine! Webastos rule, when working! I have an early 03 with one, must be one of last.
 
Axit said:
My 1.4 petrol BBY, gets to 90 and sits there, whether I`m moving or not.
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In fairness to the post I replied to above, reading back from the beginning of the thread, I now realise it started out as being about a 1.4 petrol and is in danger of becoming hijacked with TDI warmth issues, not least through my own posting :oops:

I'd agree with other posters, if a 1.4 isn't keeping the temperature gauge up to 90, the thermostat would be the first thing I'd change. Worth doing the coolant temp sender while you're in there too, it has two separate sensor circuits meaning that what it tells the gauge and what it tells the ECU can be two different things, especially if one of the sensors is failing.
 
Drove the car today. 14 degrees C outside, so didn't use any aircon or heating in the cabin. Hit 90 degrees after a few minutes then stayed there rock solid in stop start London traffic. Maybe the use of heater immediately on a cold day was the culprit.
 
Modecorp said:
Drove the car today. 14 degrees C outside, so didn't use any aircon or heating in the cabin. Hit 90 degrees after a few minutes then stayed there rock solid in stop start London traffic. Maybe the use of heater immediately on a cold day was the culprit.
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The petrol engined cars should continue to warm up and then stay at 90 regardless of what you do with the cabin heating. You have a fault, just not a major one. I would still consider a check / replacement of the thermostat and also checking the gauge's coolant sensor for correct operation.
 
dj_efk said:
The petrol engined cars should continue to warm up and then stay at 90 regardless of what you do with the cabin heating. You have a fault, just not a major one. I would still consider a check / replacement of the thermostat and also checking the gauge's coolant sensor for correct operation.
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Agreed. I've added those two things onto my to-do list.
Any ideas on part numbers for the 1.4 petrol? I'm guessing its advisable to go genuine Audi on these items?
 
And remember to only use the correct coolants when you refill. Preferably after a clean out of the old coolant. This is even more important if the wrong coolant has been used.

#5 on this diagram. Note there are 2 different versions of the thermostat and operate at different temperatures. Not sure if both still available...


To see the full part number just click on the magnifying glass to the right of the partial part number.
 
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