Wildly fluctuating oil temps

[urq]

... when it is coming up to temp you are seeing 300 a degree per minute 
rate?  I'm a bit skeptical ... I'd expect the temp change rate to slow as 
the overall temperature is higher too.

I suppose there could be something funky going on with the oil thermostat 
... but I'd be more suspicious of the sender/gauge ... how is the sender 
mounted on the V6?  Is it still like the old I-5s, where the sender is at 
the back side of the pressure relief valve?  If so, I suppose one 
possibility is that the filter is plugged and causing the oil to bypass ... 
do you have an oil pressure gauge?

Tough to say what the most appropriate test method is ... one thing I did on 
an I-5 was to use a brass "T" at the oil pressure switch and install a VDO 
temp sender there ... then you can run a wire into the cabin to hook up to 
an aux gauge ... and then you can see if both senders see the same phenomema 
...

Steve B
San Jose, CA (USA)


> Recently, my 2000 A6Q2.8 has started showing a deeply troubling symptom.
> Sometimes, the oil temp will be rock steady at just shy of 225 degrees.
> Sometimes, though, it will start fluctuating up and down pretty quickly.
> The swing can be as little as 10-20 degrees, or as much as 50-75 degrees!
> Needless to say, watching the oil temp go from 225 to 300 in 15 seconds,
> wiggle a bit, then drop back down to 225 is unsettling.
>
> When it climbs, it does so at about the same rate as it climbs when 
> getting
> up to temperature, so I do think it is actually getting that hot. The oil
> in place is a fresh fill of Castrol GTX, some 5W30 and some 5W40 (both
> approved weights).