Ecodiesel coolant temp

[92-Eco]

and i know my thermostat is working, its goes from no reading and climbs to about a needles width past the first mark then it opens and drops back down.

[Quantum TD]

and i know my thermostat is working, its goes from no reading and climbs to about a needles width past the first mark then it opens and drops back down.

Are you certain that you even have a thermostat? Low temps at or below 1/2 gauge usually mean there's no T-stat.

As for the OP, the gauge is notoriously inaccurate. Also, if you read the manual for your car (the one that comes in the glovebox) it will state that temps up to about 3/4 to 7/8 are still within "Normal"

If after changing your T-Stat, the temps are still on the high side, but the fans still work as normal and there's no residual pressure in the overflow tank after a nightly cool down, then I'd say you're ok. At that point, you may try to replace the sender for the gauge, or the gauge itself.

Here's a link to my post when I was worried about the operating temps on a 1991 ECODiesel. I ended up selling the car 2 years ago, and the girl comes in for repairs every now and again. The car still runs great. Better than any diesel I own, and it's got close to 200K on it.

http://www.vwdiesel.net/forum/index.php?topic=9958.0

[92EcoDiesel Jetta]

This is where my 92 Ecodiesel temp gauge sits on the highway doing 65 mph. I calibrated the gauge  (in boiling water with an ohmeter and thermeter) and at the position of the needle in the pic, the coolant temp is a little above 212 F.  I measured 84 ohms in a pot of boiling water when I calibrated it. Iit measured 79 ohms in the car (lower is hotter).

I am curious where your coolant temp gauge sits in your Ecodiesel and if you can, measure the resistance of your sender. It's easy if you have a DVM, After getting the car up to steady temp, pull the connector on the sender (the one on top of the flange) and measure the sender resistance.

Turns out the thermostat was stuck closed! I put it in boiling water and it did not open at all. A new thermostat (195 F) was installed and the needle now sits 1/2 way between the middle and 3/4 mark. I also found a 2 prong connector near the battery (black connector with 2 red wires) and one of the wires was corroded to the point of not making a connection and was the cause of the fans not coming on automatically. I spliced that connection and the fans now come on automatically when the needle gets near the 3/4 mark and stops when it drops down to near the middle mark.

[92EcoDiesel Jetta]

I've been putting some miles on the Jetta since doing the timing belt and a new T-stat (195F). Now the needle sits  midway between the 1/2 and 3/4 mark no matter how hard I drive it. Pic below is flooring it on the steepest hill on the Merritt pkwy in CT and the needle does not move any higher! Resistance of the coolant temp gauge sender is 94 ohms which is around 190 F, verified by a wireless contact thermometer (at the hose).
 

[Quantum TD]

That's where they tend to ride. The early Rabbit 1.6NA tend to sit right in the middle. The ECOs tend to sit just right of 1/2.