Getting Code P0128

Curious Chris

Top Post Dawg
Joined
Jun 11, 2001
Location
Pineview GA
TDI
Jetta Wagon 2003 RIP Rockford IL
Factory Service Manual says check coolant regulator which when I look at the Diagram it has to be the thermostat.

The thermostat is in the lower radiator hose that run back into the engine to the right of the oil filter housing and is pretty much under the injection pump. Obviously you are going to loose a lot of coolant so you might as well drain it. You take off the hose, then 2 bolts hold a connecting piece that supports the thermostat. Remove that turn thermostat 1/4 turn left and it will come out. Assembly is in the reverse direction, torque on the 2 bolts is 15Nm.
 

xMikeyGx

Member
Joined
Jun 11, 2008
Location
Raleigh, NC
TDI
03 Jetta TDI
Right so.... bring it to "the german" aka the dude down here I found who knows his way around a TDI. Unless its an easy job. I just had the ECT switch replaced, you think it might have something to do with that?
 
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Curious Chris

Top Post Dawg
Joined
Jun 11, 2001
Location
Pineview GA
TDI
Jetta Wagon 2003 RIP Rockford IL
Hmmm does the "the german" have VagCom aka VCDS? The ECT, G62, reports the coolant temperature to the ECM and to the dash gage. Now if the G62 is malfunctionnng VCDS would tell you that; I know my G62 was flaky for a long time and I finally replaced it. I am guessing the ECM must think the G62 is ok, and if the coolant temperature is low, well then it is the thermostat.

What does you dash temperature gage say? If it is low than I would still go with the thermostat. If not I would lean towards G62.

It is pretty easy other than figuring out what to do with all the coolant that will come pouring out. If you had the Bentley Manual for you car you would see how easy it is; or go out to your car, remove the engine cover, and look down below the injection pump.
 

xMikeyGx

Member
Joined
Jun 11, 2008
Location
Raleigh, NC
TDI
03 Jetta TDI
It seems fairly easy. I picked up a thermo at Advanced and the guy at the counter took at look and he basically said exactly what you said but after he pointed out where everything was it looked pretty easy. I'll be taking a shot at this tomorrow.
 

whitedog

Veteran Member
Joined
Jul 12, 2004
Location
Bend, Oregon
TDI
2004 Jetta that I fill by myself
A) someone here just went through a fiasco where they had a coolant temp problem and they put in an aftermarket CTS and it didn't work. They put in one from the dealer and all was well.

2) Gurus have reported that there IS a difference in thermostats from the dealer and aftermarket.

III) If you replace the thermostat anyway, be sure to know which way to turn the neck so that you don't break off the holding tabs.
 
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