Judder and temperature guage

[nutter1980]

;)Hi all , I posted a problem afew weeks back " can be viewed here http://www.vwaudiforum.co.uk/forum/showthread.php?t=20780 , I have now noticed on the way home from work this evening that the temp guage randomly drops to its lowest point the shoots back to 90 , Within 8 miles I noticed it about 3 times.

Car is 2001 Audi A4 TDI 130, after searching the forum I found this and wanted to know if it was releated.

"" I have discovered I must have a duff thermostat, since I can't get the actual coolant above 78-77C during normal driving (ie my gauge never says 90C). I have to stop and run the car on fast idle for 5-10 mins to get it above 77C.
Another interesting effect I found while doing this experiment was that when the actual coolant temp reaches 89C, the engine revs will jump up about 100rpm while holding a constant throttle position. Maybe the ECU is switching to different operating conditions at this temp? In which case, I'm never reaching it ""

The thing that stood out is this comment " Another interesting effect I found while doing this experiment was that when the actual coolant temp reaches 89C, the engine revs will jump up about 100rpm while holding a constant throttle position" Could this be the juddering problem, could it be related to the thermastat ?

Any advise would be great , thankyou in advance:confused:

[nutter1980]

Please tell me if I am talking rubbish, I have 0 car knowledge, The car has 2 months warrenty left with the trader.

[rhencullen1989]

Hi, i have just replaced the thermostat on my A4 because the temp gauge hardly moved from its stop. It only moved a couple of mm (60 deg) on a run, but in town it would reach 70 or so degrees, it now reaches and stays at 90 deg. You have 2 choices, the cheapest but hardest is to replace the thermostat, either re- use the coolant or flush and re-fill with the pink G12 plus (should have this in anyway) don't mix different antifreezes as they can gel. Or option two is the dearer but easier one and thats to change the coolant temp sensor, if the same as 1.8T petrol engine, its behind the rocker cover at the back and has 4 pin connector. Its held in by a simple clip, but put a new o ring in! Hope this is of some help to you.