Engine temp gauge up and down

Tristanspeed · 13-02-16, 12:13 PM

Hello - the engine temperature gauge on my B2 seems to be way off - while in slow traffic when the car is warmed up and just creeping along it can hover between 90 and 120 degrees, but then honking along the motorway at 75mph it drops down to the bottom, as it would if the engine were cold. I would guess this is just a faulty gauge and nothing to worry about, but I'm ready to stand corrected! No other signs whatsoever of overheating.

John. · 13-02-16, 12:17 PM

Thermostat likely?

Flying Frank · 13-02-16, 12:28 PM

Had endless issues with temperature gauges in Audis over the last 30 years, but I'd tend to agree with John from the symptoms you describe altho if the temperature falls way down when "moving swiftly" that would indicate a stuck open thermostat, but not really explain the very warm reading when the car is almost stationary....is the cooling fan kicking in when the engine gets that hot I wonder as it should do when the temp goes up to about 107 I believe.

Lots of folk say the gauges are useless and not accurate, but when the systems are all in order I've found the gauges to be spot on i.e. sticking within a nats whisker of 90'C. :-)

Hanuman · 13-02-16, 01:07 PM

I'm inclined to say the gauge is showing something sensible, and so warrants further investigation.
(BTW- I don't know your model specifically)

Is there a viscous fan involved? If so, suspect the drive clutch.
If the fan(s) are all electric, then it's worth checking that they are operating.
These are what affected my V8. Slow warm up due the viscous fan constantly running, and overheat due the electric fan not working (crack in the fuse link)- slow traffic under 15mph actually got to serious overheat pretty fast.

Thermostat- well, I'm thinking mine has stuck in the V8, because coolant rarely rises into warm temps now. It's just such a sod to get at.

vorsprung durch technik · 13-02-16, 05:29 PM

I would say Thermostat and would agree that the gauges are accurate.

The only gauge that is known to play up sometimes AFAIK are the V6 cars that can indicate low pressure at hot idle. Have read these being replaced with a new sender and oil pressure goes up nicely indicating true oil pressure.

Tristanspeed · 13-02-16, 08:56 PM

Hello - thanks for your input. The cooling fan doesn't kick in, and the car doesn't feel like it's ever doing anything other than warming up normally (about 10k of driving) and then at normal operating temperature. Should I get my local classic Audi 'garagiste' to have a butchers you reckon?

13-02-16, 12:28 PM	#3
Flying Frank 4 ring whore! Classic Audi Club Member Join Date: Dec 2012 Location: Kernow, Gods own county !! Posts: 2,388	Had endless issues with temperature gauges in Audis over the last 30 years, but I'd tend to agree with John from the symptoms you describe altho if the temperature falls way down when "moving swiftly" that would indicate a stuck open thermostat, but not really explain the very warm reading when the car is almost stationary....is the cooling fan kicking in when the engine gets that hot I wonder as it should do when the temp goes up to about 107 I believe. Lots of folk say the gauges are useless and not accurate, but when the systems are all in order I've found the gauges to be spot on i.e. sticking within a nats whisker of 90'C. :-) Last edited by Flying Frank; 13-02-16 at 05:54 PM.

13-02-16, 01:07 PM	#4
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,006	I'm inclined to say the gauge is showing something sensible, and so warrants further investigation. (BTW- I don't know your model specifically) Is there a viscous fan involved? If so, suspect the drive clutch. If the fan(s) are all electric, then it's worth checking that they are operating. These are what affected my V8. Slow warm up due the viscous fan constantly running, and overheat due the electric fan not working (crack in the fuse link)- slow traffic under 15mph actually got to serious overheat pretty fast. Thermostat- well, I'm thinking mine has stuck in the V8, because coolant rarely rises into warm temps now. It's just such a sod to get at. __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor

13-02-16, 12:17 PM	#2
John. 4 ring whore! Classic Audi Club Member Join Date: Mar 2011 Location: Scottish Borders. Posts: 7,520	Thermostat likely?

13-02-16, 05:29 PM	#5
vorsprung durch technik 4 ring whore! Classic Audi Club Member Join Date: Feb 2014 Location: Near Watford. Posts: 7,753	I would say Thermostat and would agree that the gauges are accurate. The only gauge that is known to play up sometimes AFAIK are the V6 cars that can indicate low pressure at hot idle. Have read these being replaced with a new sender and oil pressure goes up nicely indicating true oil pressure.

13-02-16, 08:56 PM	#6
Tristanspeed Grown up member Join Date: Jan 2016 Location: Lyon, France Posts: 20	Hello - thanks for your input. The cooling fan doesn't kick in, and the car doesn't feel like it's ever doing anything other than warming up normally (about 10k of driving) and then at normal operating temperature. Should I get my local classic Audi 'garagiste' to have a butchers you reckon?