Hey everyone, so my 13 Jetta doesn't have a temp gauge. So I decided to watch it with obd11. The engine only gets to 80° Celsius if I let it sit and idle it'll get to 205 or so at least that's what it was at when I shut it off. I know diesels in general take awhile to warm up and have a harder time doing so. So my drive to work is about 18 miles. 10 miles of two lane back roads and the rest is a interstate run. Car hovers between 76-81. No codes or pending codes and it was 35° F yesterday day morning and 62 °F in the peak of the day. Is this just a normal diesel behavior to run a little cool or is the thermostat getting weak? At what point do you change the thermostat? It's an absolute bear to do from the sounds of it so I want to make sure it's worth my time.
VW Jetta TDI coolant temp
- Thread starter wheelman
- Start date
Normal for a diesel
Now would be a good time to change it. The OEM thermostats in my Charger and Durango both went bad and they are not as old as your car.
OEM thermostat is 190°F right? Wouldn't 212°F be pretty warm while driving?
VW's have an overbuilt cooling system I feel. My old Jetta and more recently departed MK7 GTI would actually start to cool down driving down the mountain with little load in the winter. Never threw an under temp code. I feel if your car isn't warming up properly it would set a code pretty easy.
Yes a diesel moves a lot of air through the engine at idle, that has a cooling effect.
it looks like you are interchanging celsius and Fahrenheit ... 80*C is 176F and I would expect a diesel to get to that idling. 205*C is 400*F so I think you really mean 205F running which I would expect...where are you taking the reading? from the PCM? or a raytek on a water outlet?
205°F is what it got to while sitting idling. While driving it it runs around 170-176°F
Using obd11 monitoring coolant temp sensor
if it got to 205 (below boiling) with the cooling fan on delay engage - thats totally normal, the front end and radiator size goes not give it a lot of 'sitting there cooling off' ability. I think you are ok.
fwiw - we used to zip up the front of our big trucks in the winter or else the coolant could slush up IN the radiator while running down the road across montana in the winter.
My concern is it's not warming up enough. The. Thermostat is an 87°C
back when I was a mech, 70% of the cars sold here used small diesel engines. The temps you are seeing are normal. One check you can do is check if the radiator hoses get warm before +- 80°C is reached.
Upper radiator hose I assume? So it's normal for a small diesel to run around 75°c or so than to run at the 90° even the the t stay is an 87°c? Just want to make sure I understand fully.
Yes, especially when there's little excess heat beeding shedding. It's not normal in high summer.
Ok so in cooler weather below says 60°f that's normal? Obviously if it's 90°f outside it should be warmer? I guess I'll go feel the hose as it warms up and see what it does. This car makes me feel ignorant with how little I know about it and Diesels In general.
it depends how hard you run it, but if the fuek consumption is low enough and the temp cool enough the engine will never get warm. For my old car and my dads current car that's when we use less then 2 quarts of fuel per hour and temps near freezing.
It really shouldn't matter if it is diesel or gasoline, the engine is designed to operate at a certain temperature which should be controlled by the thermostat. Its fuel source is irrelevant at this point as is whether it has an "overbuilt" cooling system or not. My old BMW probably had an overbuilt cooling system (extra capacity) but the engine could maintain the thermostat set point even if that meant it had to drive completely closed. Even on the coldest of days here in Wisconsin it ran at the normal operating temperature.
60°F ambient is nowhere near too cold for a cooling system to function at the proper temperature.
I get what you're saying but I've owned cars in the past that when it was below freezing they wouldn't warm up and would actually cool themselves down while sitting. My 17 focus does this as an example and it's gasoline and there's nothing wrong with it. Driving home earlier today the Jetta ran about 80-82°c .
From what I understand the car won't flag a code for a p0128 as long as it gets above 70°c. Or the modeled temperature is 80°c or more. Measured temp was 80°c. Not exactly sure I understand the modeled temp but that is what Mitchell 1 pro demand says.
