Bizarrely accurate temp gauge reading

[A3Osprey]

Hi all,

Long time lurker (due to many, many various problems), but 1st time poster, due to what seems to be a bit of a strange one.

A bit of background - a couple of weeks back, my A3 1.8 (non-turbo) started seriously overheating, to the point where the warning light came on.

Got it booked in - the plastic water pump impellor had gone. New Rad, water Pump, timing belt and radiator and it seemed to be okay.

Driving into work yester, which is a longer journey than house to garage, I noticed the temp starting to increase past 90 again. Obviously my heart sank - £357 for a non fix hurts quite a bit.

However, it got halfway between the 90 and 100 marks then started coming back down, then went back up, then back down and so on.

Looking through the forum, I found out about the Climate Control display trick and how the display sometimes doesn't match the dash guage.

Reading up, it seems the normal behaviour for the gauge is to stay at 90, while the Climate control display can go up to 104 or so. This doesn't seem to be happening to me.

The guage and the temp gauge are perfectly matched - goes up to 104, fans seem to kick in, drops to 98-100, rises, fans kick in, repeat.

Do you know what would cause this? Faulty Temp sender? (wasn't replaced, although just over a year old). The thermostat is new - maybe a faulty or sticking one?

Many thanks.

 

[TDIQ]

As you know I've got a similar problem so I'm trying to gather as much information on the whole temperature reading/overheating issue as possible. I too have had the thermostat replaced (twice) and waterpump replaced.

Did you replace the temp sender yourself? Or do you have any info on how to do it and locate it as neither garage even mentioned the sender.

Thanks

 

[S3 Nattie]

Coolant sensor may be dead, giving erratic readings.

Its to the right of the engine block underneath some piping. Might be green if its a newer version, if not its black. Real easy to change.

 

[TDIQ]

Is the coolant sensor to the right of the engine block or is that the sender?



The second picture being the ringed area on the first one, is that green topped thing the temperature sender or thermostat?

 

[golf]

^^^ That's the temp sender mate.

 

[TDIQ]

If that's the sender then where can I find the thermostat then? Or are the actually just the same thing? I know it's a stupid question, but there's so many different pages with the two words I'm confused.

Thanks again

 

[RichA3Turbo]

The thermostat is behind the chunky black plastic elbow. on the above pic, its the top left on the dipstick tube, and just below the gap between the inletmanifold on cylinder 1 and 2 (Left)

Its pretty easy to change, just be careful not to drop the bolts down the back of the accessory bracket...i did this and ended up having to remove the whole lot to get the damn bolt.

 

[j4jon]

If you are going to try and change the thermostat yourself be careful with the dipstick tube as they can break very easy. I knew they where easily broken but still managed to break mine when I took it apart. Still they are only 3 quid or so from the dealer.