Lyle Jenish

2001 audi tt quattro 225hp
36k miles
original and mint

Cluster temp gauge rarely gets above 70c
When I run the coolant temp through climate display (code 51c) temperate slowly but steadily climbs to 90c (takes quite a while) and then the fan engages and maintains 90c. No overheating.
Heater core works great - cabin is warm within 5 mins.

However:
Fuel consumption is very high - just over 10 litres per 100 kilometres of highway travel - supposed to be about 7.7 litres for every 100 kilometres of highway travel.

Any suggestions on coolant sensors, thermostat or troubleshooting?

Thanks in advance.

Mister Bally

Replace the thermostat. It is stuck open if it used to work fine. If you recently purchased the vehicle; who knows, the previous owner could have removed it completely.

J. Patterson

Lyle Jenish

Thanks - block 49 is bang on with the cluster temp gauge. Running cool, new thermostat needed

Lyle Jenish

Replaced thermostat - running proper at 90 degrees on both analog gauge and block 49.

Question - all came apart and went together fine, save for the alternator strap retainer nut - dropped into the abyss behind the alternator mount.
I believe it is a 8 mm nut - does anyone know the exact specs - the thread pitch?

JoeKan

Thanks for the diagnosis. I've got exactly the same problem with mine (63K kms on the odo).. Read in another posting that if the temp gauge is running low, and '51C' is reading at proper temp, then the instrument cluster will need a rebuilt as the gauges are not accurate. I'll try '49C' tomorrow - didn't know about that one.