b5 tdi 1100 revs when cold

[Google44]

Hi there

My 1.9 TDI developed something strange recently. Only on start up after is starts normally the revs would go to 1100 for a short period of time. Outside temperature is around 10. When engine warms up in few minutes it runs normal. The temperature gauge shows around 60-70, only in town around 80. When ‘Test 51-engine coolant temp’ is used on climate control it is showing 90?  Could it be that engine coolant sensor is faulty?

Last year thermostat and temp gauge were changed - temp was showing 90 since. How come that ‘Test 51’ and ECT on display don’t show same temperature? Is the same sensor used for both gauges?
BTW, no error codes on read.

[towcestervag]

try temp sensor

[towcestervag]

sorry forgot check the wiring loom to pump as these break as comencement of injection will cause this

[Google44]

I've checked the pump. There is no electric going to it except one wire - think it's for engine cut off. When you say temp sensor - do you mean external temp or engine temp?

[Google44]

external temp is showing OK. What puzzles me is the 'test 51' - shows 90 C bang on while dial on dash shows 70 or even nothing. Are they controlled by the same temp sender

[frankc]

My A4 did this too, sorted with a new coolant temp sensor - its mounted at the rear of the engine held in place on a coolant hose by a spring clip. Check which one you have before ordering as they are colour coded, mine was blue and has 4 pins in the connector.

I believe the sensors have two circuits in them, one for the temp gauge and one for the ECU.

Make sure you get a spare o-ring with the new sensor and hold a tub under the hose while changing - you will lose some coolant when you change them over.

Frank

[Google44]

My A4 did this too, sorted with a new coolant temp sensor - its mounted at the rear of the engine held in place on a coolant hose by a spring clip. Check which one you have before ordering as they are colour coded, mine was blue and has 4 pins in the connector.

I believe the sensors have two circuits in them, one for the temp gauge and one for the ECU.

Make sure you get a spare o-ring with the new sensor and hold a tub under the hose while changing - you will lose some coolant when you change them over.

Frank



I think you may be right. I've replaced it (was changed last year) and it seems fine now. Dash also showing 90.

Thanks