'01 Jetta: proper thermostat operating temp?

[Quattro Pete]

Anyone know the normal coolant (thermostat) operating temp range on an '01 Jetta 2.0? I think it's a 90C thermostat, but I'm sure some fluctuation is permitted.

I did some measuring with a VAG-COM the other day - basically on the hwy, going about 65-70 mph, the temp doesn't go above 75 deg. C (about 170F), although in all fairness, it was a pretty cold day (10F outside).

Basically, I suspect this thermostat is on the way out - the car is getting poor mileage (19 mpg in mixed driving) and there is noticeable moisture/cream condensation under the oil cap. The car is driven on rather short trips during the week, but gets driven more on weekends, yet the moisture does not evaporate.

Now, I don't want to replace it myself. The car is under extended warranty, so I want the dealer to do it. But they won't just take my word for it. For them to do it, they'd have to diagnose the car, and if according to them the car is still within spec, I'll have to eat the diagnosis cost ($120). The khrappy thing is that the coolant needle is still close to 12 o'clock position. Hence my question, will they consider 75C to be still "within spec"?

 

[StevieC]

It was 10F here last week and my car got to 192oF and stayed there... I would imagine yours should be operating in the same temperature range. 170 is too cool IMO.

 

[The Critic]

Stant lists the OEM thermostat temperature to be 190 Degrees.

The OE thermostat is listed as 87C or 188.6F.

http://www.mjmautohaus.com/catalog/produ...roducts_id=1557

Since the car is an '01, it's probably near the 8/80k recommendation for a timing belt service. If you get a proper timing belt kit for this car, it will include a thermostat. So, you might want to hold off on this repair until then.

 

[ARB1977]

Originally Posted By: Quattro Pete
Anyone know the normal coolant (thermostat) operating temp range on an '01 Jetta 2.0? I think it's a 90C thermostat, but I'm sure some fluctuation is permitted.

I did some measuring with a VAG-COM the other day - basically on the hwy, going about 65-70 mph, the temp doesn't go above 75 deg. C (about 170F), although in all fairness, it was a pretty cold day (10F outside).

Basically, I suspect this thermostat is on the way out - the car is getting poor mileage (19 mpg in mixed driving) and there is noticeable moisture/cream condensation under the oil cap. The car is driven on rather short trips during the week, but gets driven more on weekends, yet the moisture does not evaporate.

Now, I don't want to replace it myself. The car is under extended warranty, so I want the dealer to do it. But they won't just take my word for it. For them to do it, they'd have to diagnose the car, and if according to them the car is still within spec, I'll have to eat the diagnosis cost ($120). The khrappy thing is that the coolant needle is still close to 12 o'clock position. Hence my question, will they consider 75C to be still "within spec"?

Im kinda in the same boat as you Pete with my wifes 97 Jetta.
On cold days with the heat on, city driving the temp will reach 160. It will pretty much stay there for awhile. Freeway driving its closer to 210...kinda weird.

 

[rcy]

My wife's Beetle had the 2.slow motor as well. There is no temp gauge in a Beetle, but I installed some nice Stewart Warner gauges. The car was running fine, blew decent heat from the heater etc., but after installing the gauges I noticed it ran around 170 on the highway, but climbed up to 190 in the city.

The parts guy insisted I didn't need a thermostat - they hardly ever fail blah blah blah. I insisted he take my money and installed a new thermostat and it ran 190 everywhere. Mileage increased too.

 

[wavinwayne]

My '00 1.8T GTI sits at 190°F year-round. I can't say with any certainty what operating temp. should be on the 2.0.

Also, FWIW my 1.8T gets at least 24mpg in mixed city/hwy driving, and 28-29mpg hwy. I would assume the 2.0 should be getting at least that.

 

[ARB1977]

Originally Posted By: rcy
My wife's Beetle had the 2.slow motor as well. There is no temp gauge in a Beetle, but I installed some nice Stewart Warner gauges. The car was running fine, blew decent heat from the heater etc., but after installing the gauges I noticed it ran around 170 on the highway, but climbed up to 190 in the city.

The parts guy insisted I didn't need a thermostat - they hardly ever fail blah blah blah. I insisted he take my money and installed a new thermostat and it ran 190 everywhere. Mileage increased too.

Interesting.

 

[rcy]

Yeah, I assume the wind blowing over the rad/engine at highway speeds caused it to run cooler (this was during the winter by the way).

When I took the old thermostat out, it was slightly open even when cold. I guess this was letting enough coolant flow to the rad to run the engine cooler on the highway as air blew past the rad. I dunno, but I do know with the new thermostat installed, the car ran at 190 on the highway instead of 170 with the old thermostat.