Problem with temperature on 1.9 TDI ASZ

Hello I have not had a problem like this before on a car. Right now it is cold around 0C but this has happened even at 10-15C outside temp. If i put the heat on my temp drops from 90 to 80 or 70 degrees.

Some people say this is normal but it doesn't seem like that to me. I was told that if it is a thermostat it will lose temp while driving not while standing in place. I do not lose temp while driving but when i stop, or go downhill with engine braking. And it happens in less than 1 minute. I don't have a check engine light on and no fault codes either.

Should i just replace the thermostat?

It's cheap and easy to do. I know that my ALH is a cold blooded turd, with temperatures that cold you may benifits by covering up 1/3 the radiator to retain heat.

Agreed, get the highest temp thermostat you can and definitely cover a third, to have, of the radiator.

Sent from my Armor_2 using Tapatalk

eddieleephd said:

Agreed, get the highest temp thermostat you can and definitely cover a third, to have, of the radiator.

Sent from my Armor_2 using Tapatalk

Click to expand...

What do you mean by the highest temp thermostat? I saw some online that are 80-102 C and stock which say 87-102C.

So I should replace the thermostat? I know its a fast job i will just take it to my mechanic.

I'd replace thermostat and temperature sensor. Consider blocking grille after that.


Sent from my Moto G (5S) Plus using Tapatalk

Figit090 said:

I'd replace thermostat and temperature sensor. Consider blocking grille after that.


Sent from my Moto G (5S) Plus using Tapatalk

Click to expand...

If by temp sensor you mean the one that is near the bottom of the engine (i don't remember the exact name of it) on the side i replaced that last winter. It gave a fault code. What do you block the radiator with? I have never done that.

I've seen Jettas with pipe insulation on the front grill. You could do something similar, or just put some cardboard or something between the grill and radiator.

Alright then guys thanks for the help I will write if it fixed my problem.

The thermostats I see are 80*C and 87*C. I recommend 87* as the difference is usually that the lower temperature thermostat usually has a couple holes and causes it to take longer to reach operation temperature.

Sent from my Armor_2 using Tapatalk

DarthJe5us said:

If by temp sensor you mean the one that is near the bottom of the engine (i don't remember the exact name of it) on the side i replaced that last winter. It gave a fault code. What do you block the radiator with? I have never done that.

Click to expand...

Yeah it's the little metallic probe sealed by an o-ring and held in with a flimsy plastic clip. If you changed it don't worry. I suggested it because it's good to replace them while you're working in there if it's old

Upper grille can be blocked with pipe insulation (between headlights) or cardboard in front of radiator as others mentioned. I haven't done it personally so I can't advise on how much for a given situation.

Sent from my Moto G (5S) Plus using Tapatalk

Start with a quarter to a third and watch the temp gauge to see if you need more or less.


Sent from my Armor_2 using Tapatalk

I will see if the temps stabilize after the thermostat replacement if not i will start blocking it.

Honestly, in those temps you should start with blocking as it will not be overheating and will warm up much faster.

Sent from my Armor_2 using Tapatalk

Just to offer a different opinion. I wouldn't look into blocking off the radiator unless you get a lot of -10C and lower.
On my car as the thermostat got old, it got sluggish, road running temp would never reach proper temp. The fact that it cools when stopped makes me interweb guess poor circulation.

BobnOH said:

Just to offer a different opinion. I wouldn't look into blocking off the radiator unless you get a lot of -10C and lower.
On my car as the thermostat got old, it got sluggish, road running temp would never reach proper temp. The fact that it cools when stopped makes me interweb guess poor circulation.

Click to expand...

? Why poor circulation? That would make it run hot, not cool.
Drops like that are attributed to the thermostat failing open and too cool a thermostat with holes allowing coolant to flow when closed, and heater core circulation when cold on the draw through rather than recirculation.
Blocking the radiator 25% in 10* to 50* should allow a properly working thermostat to control well, once the temps are getting to 65* it will need to be unblocked.

Sent from my Armor_2 using Tapatalk

DarthJe5us said:

If by temp sensor you mean the one that is near the bottom of the engine (i don't remember the exact name of it) on the side i replaced that last winter. It gave a fault code. What do you block the radiator with? I have never done that.

Click to expand...

I use a corrugated plastic for sale sign from Dollarama. You can pull the middle bottom plastic grill off, then roll up the sign, then tuck it in there and unroll it up the rad, takes all of 5 minutes or less. I also use pipe foam on the upper grill. Both may be overkill for where you live but where I am it gets pretty cold. I'm just cautious in the spring or when it warms up I may pull one off.

I had T-stat issues with not heating up and replaced with an OEM one from the dealer and works great. And the coolant temp sensor is the other thing people are mentioning replacing but sounds like you may have already done that. If you have any doubt might as well replace it while you do the T-stat as the part isn't too pricey. Good luck!

On a side note, not sure your exact symptoms, but if your car is at operating temperature and it's let's say -15c out and you parked and let it idle for 10 min if your heater is on it probably won't hold temp it will drop a bit. If you shut the heater fan off or put it on recirc it will hold temp better. But sounds like you may have other times its losing temp

I just tried that last night. It was -3C, turned off the heating and the car lost maybe 5*C in 5 minutes. But when i turned on heating at 25C it dropped to 75C in 1 minute.

Waxed cardboard from the produce in grocery stores works great and it's free.
You can insulate the heater lines also.


Sent from my Armor_2 using Tapatalk

DarthJe5us said:

I just tried that last night. It was -3C, turned off the heating and the car lost maybe 5*C in 5 minutes. But when i turned on heating at 25C it dropped to 75C in 1 minute.

Click to expand...

Hmmm. So at +25C the temp dropped that much or am I misinterpreting?