CEL and coolant issues

So i got the stupid P0128 code yesterday. It went away so i thought it was nothing. Came back on today so i drove around for a bit and checked the rad hoses. Top is hot and bottom is cold. Great sounds like a T-stat right. Well heres where i need help. The gauge on the dash is reading smack on at 190 and doesnt seem to be overheating. So i have no idea. You would think if the Tstat was broke that it would overheat or underheat. Could it be a waterpump? I have no idea how to tell.

How many miles? Has the timing belt been replaced yet?

Diesels do no make as much waste heat as do gasoline engines. It is possible that it is normal. The engine is staying at the design temperature with little exchange to the radiator.

I'm working on an '01 TDI Jetta right now and one of the many problems I'm trying to fix is the temperature. The gauge in the dash reads 90degC (fully warmed up) but using VAG-COM the engine is only 80degC. I used an infra-red thermometer to verify that the engine is running cool at 80degC so I will be changing the thermostat since I'm already doing a TB change with water pump. The original water pump was intact at 330,000km and the thermostat did open up too early. My own '01 also takes a long time to warm up fully, so I'll likely be putting a thermostat in it soon.

Fire32:

Do yo have access to VAGCOM? If so, plug it in whne the car is stone cold and check group 7 in the engine module. It will show fuel, air and coolant temperature. Go for a drive, logging these block until the car is up to full temperature. Then take a look at them and see if there is a sudden drop in temperature. Mine is showing a drop of up to 30C in 1-2 seconds and back up in about 34 seconds. I have a bad Coolant temperature sensor.

Auto Tech:

It is normal for the gauge to read 90C when the VAGCOM is reporting the temperature as 73C. This is what happens with my 2004 and others with older cars have reported the same. The computer basically makes the gauge become an idiot light. it will show 90C while VAGCOM is showing anywhere from 73-95+. The ECU knows the actual temperature and uses that number for it's fueling calculations, but since many people see a normally moving temperature gauge as a problem, they dumbed down the gauge so it looks like the temperature is nice and steady.

TornadoRed said:

How many miles? Has the timing belt been replaced yet?

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Its a 2003. 64,000 Miles. No the TB has not been replaced. I have the green colored CTS. Yes i have VAGCOM access. Perhaps i should go for a spirited drive to see if the Tstat still will not open?

Ok to check my coolant flow and hopefully rule out the waterpump i shot this video. TDI gurus tell me what you think. Also notice the horrid squeaking.

anyone?