operating temperature?

Brett Dikeman quattro at frank.mercea.net
Tue Dec 5 00:10:14 EST 2006

On Dec 4, 2006, at 9:07 PM, Jeremiah Curry wrote:

> The other day a friend was riding in our 99 Passat V6 and asked why  
> it never
> reached operating temperature.  The center of the temp guage is  
> labeled 190
> and it never got close.  That made me wonder and I noticed that my  
> 1991 200
> 20v never gets to the middle of it's temp guage either.  Should it?  
> (it is
> about 20 degrees outside, but they have both been on fairly long  
> drives, 1
> hour or more)  I am wondering if either or both of them have bad
> thermostats, they both blow warm from the heater, but not really hot.

The turbo 20v is a little "infamous" for running cooler than other  
I-5's, at least according to the gauge, in some circumstances.  Some  
have said it is because of the placement on the external coolant  
manifold, others say it is because of the auxiliary radiator.

Wintertime readings just over the three marks to the left-most are  
not uncommon, especially at highway speeds; I'd expect it to be up  
higher around town and in stop+go traffic.

   Almost straight up is about the normal "ceiling" temperature in  
summertime or after idling for quite some time (which Audi says not  
to do.  Owners manual says: get in, turn the key, drive gently until  
temp gauges come up.  Idling to warm up causes excessive wear,  
because tolerances are too tight when not at temperature.   I can  
have heat out my vents in under 2 minutes if I drive out and up a  
section of road that is a very gradual incline, or not have heat for  
quite a bit longer if I just let the car idle.  Power = heat!)

A better indicator of engine temperature is sometimes the oil gauge.   
It should stabilize at or above 60, ideally sitting pretty on 100.   
Experience may vary with outside air temperature and speed, but  
cruising on level highway doing 70 in 5th, I'd expect to see it  
sitting dead on 100 in mild weather.


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