Changing Thermostat

MG ClearTDI · Oct 3, 2008

I am fixing to change the thermostat on my 04 Jetta. My question is can anyone tell me how much G 12 will be lost? Is there any way to capture it and reuse it?

Drivbiwire · Oct 3, 2008

Why are you messing with your thermostat?

DB

jasonTDI · Oct 3, 2008

Why?

There is no reason to change it 90% of the time. If the gage is erratic it's often the coolant temp sensor, not the thermostat.

jasonTDI · Oct 3, 2008

dam-it Pete!

Drivbiwire · Oct 3, 2008

Lol

Db

Drivbiwire · Oct 3, 2008

Stop it!

DB

Drivbiwire · Oct 3, 2008

Damn thats fast!

DB

jasonTDI · Oct 3, 2008

ooppss sorry in another section.....what we said. don't mess with it.

MG ClearTDI · Oct 3, 2008

The reason for changing it is that the CEL came on, went to auto zone to have it scanned it pulled up bad theromstat. Took it to the dealership the diag. malfunctioning thermostat. Prior the this I replaced the cts with dealer part light stayed off for about a week then came back on.

Drivbiwire · Oct 3, 2008

What is the temperature of the car doing (indicated).

DB

MG ClearTDI · Oct 3, 2008

Before I changed the cts it was reading from nothing to 180 or anywhere in between. Since the cts has been replaced ( sensor purchased at dealership) it is at 190.

jasonTDI · Oct 3, 2008

Then it should be fine unless you clear the code and it keep coming back.

MG ClearTDI · Oct 3, 2008

The code was cleared 3 times at auto zone and it was still diagnosed at the dealership as a malfunctioning thermostat.

Drivbiwire · Oct 3, 2008

MG ClearTDI said:
The code was cleared 3 times at auto zone and it was still diagnosed at the dealership as a malfunctioning thermostat.

What was the code exactly, a dealers "diagnosis" is borderline meaningless!

DB

Drivbiwire · Oct 3, 2008

There is a recall on the CTS, the dealer may have been trying to get you to pay for a new thermostat which is not covered under the recall to pad their pockets with YOUR CASH.

Dealers hate warranty work since they get paid a fixed rate by VW. You however will pay whatever the want to charge you which is often double what VW would have paid for the same work.

DB

MG ClearTDI · Oct 3, 2008

I purchased the cts and replaced it myself. It usually takes about 5 miles for the temp. gauge to get to 190 degrees. If the thermostat is malfunctioning and stuck in the open position would, should it take 5 miles to reach normal operating temp.?

hid3 · Oct 3, 2008

I guess that replacing thermostat is a good idea when doing a TB job (also like replacing the water pump.). BTW, how much did the thermostat cost for you? (I guess that wasn't expensive)

MG ClearTDI · Oct 3, 2008

I haven't purchased one yet but I believe tdiparts.com has it for around $16.00

VDUB TECH · Oct 3, 2008

Drivbiwire said:
There is a recall on the CTS, the dealer may have been trying to get you to pay for a new thermostat which is not covered under the recall to pad their pockets with YOUR CASH.

Dealers hate warranty work since they get paid a fixed rate by VW. You however will pay whatever the want to charge you which is often double what VW would have paid for the same work.

DB

dealer techs love replacing thermostats under warranty because it pays great!One of the few jobs that pay good.The fault is probably cooling system malfunction which is usually a lazy thermostat.You wont loose too much coolant depending on how fast you do it.Make sure the new thermostat is in the right position.It should be installed with the front of the stat in a horizontal position.

RamMan4x4 · Oct 3, 2008

MG ClearTDI said:
I purchased the cts and replaced it myself. It usually takes about 5 miles for the temp. gauge to get to 190 degrees. If the thermostat is malfunctioning and stuck in the open position would, should it take 5 miles to reach normal operating temp.?

If a thermostat is stuck in the open position, you may never reach 190deg on the coolant temp. As asked for before, what exactly is the code that keeps coming up?

Drivbiwire · Oct 3, 2008

MG ClearTDI said:
I purchased the cts and replaced it myself. It usually takes about 5 miles for the temp. gauge to get to 190 degrees. If the thermostat is malfunctioning and stuck in the open position would, should it take 5 miles to reach normal operating temp.?

Like I have been asking what code are you GETTING!

Your thermostat is working PERFECTLY!

A failed thermostat results in the engine NOT warming up, you don't overheat with a bad thermostat in a TDI.

You are driving an engine that does not burn a lot of fuel, hence it takes some time to warm up. If you tell us it never reaches operating temps (12 o'clock on the gage) then we can discuss a bad thermostat.

By the way, are you getting a P0128 code?.

DB

MG ClearTDI · Oct 3, 2008

Code P0128

MG ClearTDI · Oct 3, 2008

The fuel mileage has dropped from mid 30's to 27-29 miles per gallon, in town. Operating temperature 190 is reached in about 5 miles.

Drivbiwire · Oct 3, 2008

Code: P0128
Error Message: Coolant Thermostat/Valve Temperature below control range
Malfunction Criteria and Threshold values: Measured Temperature lower than model temperature - <10C
Secondary Parameters and endable Conditions:
-ECT @ Engine start <40C
-ECT - > -10C
-Coolant temperature sensor not defective
-Intake temperature sensor not defective
Monitoring time length: 15 minutes
Frequency of Checks/MIL illumination: once/DCY 2 DCY

Here is the problem, you are indicating proper and normal temperatures. You replaced the coolant temperature sensor "G62" which is a dual sensor unit providing temperature readings to two different systems.

It does appear that the coolant thermostat is opening too soon and failing to permit proper warm up within the ECU's expected criteria.

I will say that this code is EXTREMELY rare!

My suggestion is to check the new thermostat, use an OEM part, I have had VERY bad luck with new thermostats, no kidding about 50% of them are faulty in my experience!

Before you install it I would check both the old one and the new one using the following checking values:

Thermostat checking
*Heat thermostat in water
-Opening begins at 85C
-Fully open at 105C
-Opening lift minimum 7mm

DB

irbk · Oct 6, 2008

I just had mine at DuPage AutoWerks, they said it was a bad thermostat, not a bad sensor. They replaced it, and 2 days later the CEL came back on. I was just purchasing the car when the CEL came back on and DuPage AutoWerks was on the way home and they checked the error and said that the thermostat that they put in must have been bad. Since I live 2 hours away from DuPage AutoWerks, there wasn't any way they could fix the car for me so they refunded me the cost. So, should I try to replace the thermostat myself (note, I'm not very mechanically inclined, I could change my own oil if I wanted too back in my gasser, but I found it was easier to pay Valvolene the $20 to do it then do it myself) or should I try to find someplace local to change it?

Drivbiwire · Oct 6, 2008

You have to use G-12 coolant (70% G-12 and 30% distilled or RO filtered water), Valvoline won't have it (whoever that is).

DB

Changing Thermostat

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