Engine Coolant Temperature Gauge question

[Eugene Kanter]

SJ,

I have just changed my thermostat from what it turned out to be a Stant
176F to a correct Wahler 87C part number 035 121 113 B.

The symptoms you describe match my 176F thermostat. When my original
thermostat disintegrated at around 250k miles, I picked up a replacement
from local parts store. I learned the hard way that local stores
computers do not distinguish between different thermostats and only
stock 176F instead of OEM 87C (192F).

87C thermostat will have your temperature meter just below 4 mark on the
highway. Album specifies 87C for NF engine.

Eugene.

On Mon, 2008-01-21 at 15:03 -0500, syljay wrote:
> Patient is a 1990 100Q. The wife's car.
> 
> The coolant gauge always seemed to be reading on the low side.
> I drove the car today with the outdoor temperature hovering around 
> 15F. Seemed to take a long time for the gauge to start registering.
> I'm wondering if the thermostat is stuck in the open position.
> 
> For the purpose of discussion, I'll provide a textual reference for 
> the coolant gauge markings.
> 
> [ ][][]  |  [ ]  |  |  [ ]  |
> . .                  . .
>   C                            H
>   1 2 3   4   5   6  7   8   9
> 
> Marking sizes are:
> single wide marker = 4, 6, 7, 9
> double wide marker = 2, 3
> Triple wide marker = 1, 5, 8
> 
> The heater came on after the usual delay . .which takes about a mile 
> of travel.
> 
> While driving down the highway at 65, the gauge stayed barely above 
> the "3" indicator mark.
> 
> When I arrived at my destination, I left the engine running and 
> watched the temp gauge. After a few minutes, the gauge crept up to the 
> "5" indicator marker, and the radiator cooling fan kicked in.
> 
> Back on the highway, the gauge stayed barely above the "3" marker.
> 
> Question 1:
> Should the thermostat keep the coolant temperature relatively 
> constant? Even at low temps and highway driving?
> 
> Question 2:
> What is the usual position of the needle when driving? And what is the 
> position of the gauge when the radiator fan kicks in?
> 
> Question 3:
> I think the dots for positions 1 and 7 are calibration test marks. If 
> I remember correctly, the Bentley shows usage of a "Special Tool" to 
> test the gauge. More than likely the tool is just a rheostat. Does 
> anyone know the resistance values at the two test positions?
> 
> Question 4:
> Does anyone have a simple method of measuring the coolant temperature 
> with an external thermometer?
> I was thinking of taping and then insulating my electronic cooking 
> temp gauge probe to the Upper radiator hose. With enough insulation 
> the outside of the hose should be at the same temperature as the 
> coolant inside.
> Shhhhhhh . .don't tell the wife!!
> 
> 
> SJ in NJ
> _______________________________________________
> quattro mailing list
> quattro at audifans.com
> http://www.audifans.com/mailman/listinfo/quattro
> ---
> Watch this space for ads :)