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Hi, I'm new to this forum and have just bought a 2010 Jetta TDI. I have searched for threads on Jetta's that never warm up and/or run cold. I haven't found anything so hopefully I'm the only one having this problem.

I live in upstate NY and have found that on mornings 20 degrees (Fahrenheit) or less I can let my Jetta run for a half hour and it will never warm up to operating temp (190). Unfortunately even when I drive it 30 miles to work (75% highway - 25% city) it will never get to 190. It will get to 170 or so but will never get to 190. I have also noticed that when it gets to 170 or so and I stop at a traffic light it will loose 5-10 degrees very quickly. That makes for a chilly ride when it's zero.
My work around lately has been to put cardboard over the lower half of my grille if it's below 20. (Blast from the past... Kinda like any Ford truck from circa 1978). That seems to work fine as the engine will warm up quickly and hold temperature for the entire ride. Comfortable ride but very old school approach.

I'm wondering if anyone else has had this issue. My gut is telling me that my thermostat isn't closing all the way.

Any feedback is greatly appreciated.

Brad
 

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I think your gut is telling you the correct answer.

In such a new car there isn't anything else I can think of. Hopefully it is a faulty thermostat and nothing (impeller) which have come loose and become lodged in the thermostat keeping it from fully closing.

Good luck.
 

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Hillybillybrad,

My golf is mechanically the same as your Jetta. My Golf will not warm up in 20 degree weather at idle unless its idled about 25-30 min. and even then it will only get a little more than halfway to 190. I drive on the highway to work in the mornings and at 20 outdoor temp it takes about 15 minutes of driving at highway speed for the car to reach 190. If I just drive around town it will not warm up to 190. Even if it reaches 190 and I park it and let it idle, at 20 degrees or less outdoors it will start to back down to about 170 or a little less at idle. It is normal for a diesel to warm up slower and not produce as much heat at idle. However, I'm not sure when you say you have a 30 minute commute if you're driving around town at slow speeds or in traffic, or if you're on the highway. If you're on the highway and can't maintain 190 after 15 min of driving, I'd say there's an issue.
 

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Welcome to the forum Brad. welcometomyturbodies

Diesels do take longer to get to normal operating temperature this is because they are more thermal efficient which means more heat does more work and not absorbed into the cooling system.

There is something not quite right if you say you stop in traffic you loose 5-10 degrees to loose temperature like that would mean you have something cooling it, is the cooling fan running? An engine won't loose heat just by standing.

If you think the thermostat isn't seating then the radiator will very slowly warm up and you will feel this. Then again you are only saying what you see on the gauge if that or something that controls the gauge is faulty than thats something else.

Either way its under warranty take it back to the dealer and let them investigate. ;)
 

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Brad,

Read your post again and just noticed the 75% highway part...I would say on a 30 mile commute that 75% highway, even in 20 degree weather you should be hitting 190 with no problem. Take it in.
 

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About a month ago I put a Frost Heater on my 06 and it works Awesome! I dont have to drive to work freezing anymore. This is a option for you if the cardboard doesnt work out. I think all diesels should come with a block or coolant heater it makes life a little easier.
 

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Try some 1/2 inch pipe insulation on your grill just dont cover your intercooler lower pass side work's great for me. Also frost heater makes heat right away.
 

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About a month ago I put a Frost Heater on my 06 and it works Awesome! I dont have to drive to work freezing anymore. This is a option for you if the cardboard doesnt work out. I think all diesels should come with a block or coolant heater it makes life a little easier.
Try some 1/2 inch pipe insulation on your grill just dont cover your intercooler lower pass side work's great for me. Also frost heater makes heat right away.

These things will work/help, but obviously I would recommend making sure there isn't a problem with the car first, because it sure sounds like there is :eek
 

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Though it doesn't look the best, the 1/2 inch pipe insulation works great for my 2006 as well. Usually goes on in November and stays till late April.
 

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First, the dash gauge is filtered and shows 190°F for an actual coolant temperature of about 165° to 230°.

It may help the car to warm up if when the gauge moves to the first line, reduce heater controls to 72°F & fan speed of 1 or 2. Until the gauge gets up to the 190° mark.

Should the thermostat need replacing, you're looking at 4+ hours. As part of the intake has to come out, alternator has to be moved to the front of the car, and a plastic coolant tube needs to be unbolted from the block.

Covering the grill does help a lot. Especially when outside temperature drops to -10°F or colder.

A plug-in block heater is also, nice to have.
 
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