A3 Tdi temperature gauge

[rfisher]

My 2001 A3 reads 75oC when fully warmed up.

It's had 3 thermostats (85oC opening) and a new sender but is still bust.

Anyone know if there's an earth for the gauge on the dash somewhere that may be making a poor contact?

[Tame Technician]

You need to know what the actual coolant temp is, Either with a lazer thermometer on the cooling system or preferable via the MVB. If the coolant temp is 90-95 then you know the gauge is faulty in some way, if the coolant temp is 75, then the gauge is ok and there is another problem

If its the gauge, its probably the dash faulty.

With the 5051 we can output control the gauges and see how they move, TT's and A3 often show up temp or fuel gauges that aren't positioned correctly, i.e when the 5051 sends the gauges to half way up, all the needles apart from the temp gauge show half, and the temp gauge shows like a quarter, sounds like this is your problem to me.

Someone on here may know how to do the same test with VAG COM. It does most things out £8000 5051b's do.

[rfisher]

Right.

Further testing has shown that;

1. The gauge is working properly and showing the correct water temperature.
2. The thermostat is working properly and opening at 85oC.
3. The engine is running cool at around 75oC.

There's clearly a leak of cooler water entering the recirculating water circuit before the thermostat is opening.

I reckon this is around the water pump somewhere.

Anyone know if this happens with this engine?

[Tame Technician]

Usually poor sealing of thermostat in the housing, so although the stat is closed, coolant still goes past it. I'd look at that before the water pump.

How do you know what the actual coolant temp is if you dont mind me asking.

Or you could just, tape off the bottom half of the rad and forget about it. I'd be far happy with an engine running cool at 75 that hot at 105, which they often do.