I posted this yesterday in general tech and got no love, so I'm posting here as it's occurring on an A6. I am really very concerned about this so please if you have any thoughts...
2000 A6 2.7t 6speed stock
Oil temperature seems to fluctuate wildly. While driving under load as well as easy cruising, at stops, basically under all conditions. But not constantly. Some times in a long drive the needle will drop all the way to min, and come back up a few minutes later. Could it be a sensor going? If so, how can I be sure, and how can I know if it is the temp changing inside the engine or if its a false read. I find it hard to beleive that the temp is swinging that much so quickly. What about the oil cooler? could this be the problem.

 

One other thing that may be relevant, the car is throwing an engine code. I was told by a friend with a reader that is says it is the Cat not warming up in the correct amount of time??? He says he has never seen that one before, he is an Audi cert. tech.

 

Hi VTA62.7,

Hey brother I just want to show you some love and let you know that were all thinking of you and want your A6 to be at its best.
First, the problem that you're describing sounds to me like the "Oil Temperature Sending Unit" going bad. The fluctuations in the readings are not normal...escpecially if you have coolant temperatures that are not fluctuating at the same time and remain consistent.
The Oil Temperature Sending Unit is an easy fix if you're mechanically inclined and should be the only expense as far as parts go. Its located at the front of your engine and should be threaded in just to the right (left if you're facing the car) and slighty above the oil filter. I'm sure that once the sending unit is replaced your oil temperature fluctuations should be resolved.
If you're not comfortable replacing the sending unit yourself, I'd take the car to a reputable shop after purchasing the part, and ask them to replace it. The labor to do this minor repair should not be more than one hour. Good Luck with it!! Oh...and peace and love to ya'.

 

Thank you sir...
I have an awesome guy, Audi master cert... He is on Vaca out of town and I just bought the car while he is gone.
I really appreciate the reply, and wonder if you could expand on one thing? If it is the sender, is it safe to assume that the oil is running at the proper temp, should I ignore the gauge until the sender is replaced? I would like to not damage anything internally until service.

 

If you have an awesome mechanic, you should have put down a small deposit with purchase contingent on your mechanic inspecting the vehicle. That could have saved you some grief and some money.

If the water temperature is steady on the middle of the gauge, then it is doubtful that your oil temperature is out of control. Next time the car is warmed up, stop it and check the oil. Feeling the end of the dipstick will tell you if it is in the 200o range -- it won't burn much -- but if it is much hotter, you could smell burning oil.

Obviously the gauge should run in the 200-225o range with the car warmed up, depending upon external temperature + how hard you are running it. In the winter, running mine at 75-80 seldom pushes the needle past 225o. In the summer heat, running it at 90-100 will drive the needle almost to the halfway mark until it cools off and drops back down to the 225o range.

 

Problem being He was working for the dealership I purchased from until recently, and is currently in the process of stealing their customers,lol. I was trying to be careful as the owner asked why I had not been bringing my A4 in anymore...

The coolant temp is rock solid, and I checked the oil dip stick yesterday after a 300 mile drive. The stick was not overly hot and there was no odd smell. I guess then based on your comments that I should be OK to drive cautiously until I can get the sensor swapped out. You guys are truly awesome here , thanks... It is a great service you guys are providing by sharing your accumulated knowledge with the masses.

 

Hi again VTA62.7,

I seriously doubt that driving the car with a faulty oil temperature sending unit will harm it, as long as the coolant temp is normal. If the fluid level is fine and there is no oil pressure warning light on in the instrument cluster...driving the car should not harm your engine. You should keep in mind that not all cars come with oil temperature gauges, this is just something usually reserved for higher end and sports cars. The majority of cars built usuallly come equipped only with an oil pressure gauge or an indicator light to alert the driver if the pressure drops below a specified level.