Coolant temp not rising above 71°C?

Hi all,
I noticed my coolant temp needle never got to its normal position even after my 25 min drive.Outside temp was -8 °C (17.6 °F).My cabin heat dial was at 2 o'clock position and cabin fan was at no.2 speed during the commute.

I also used torque app to double check the temp and it was showing 71°C.And no ECU error codes either.I was thinking of weak thermostat but i believe this EA288 TDI engine has an electric thermostat??

I can't remember if i noticed engine temp that low during my commute last winter.Did anyone else notice this phenomenon?Or this little common rail is so efficient that its not producing enough heat?

and yes i also plugged in block heater cable(that came from factory) for 2 hrs before leaving to work in the morning.Thanks.

The thermostat is a regular spring/wax element unit and starts to open at approx 87 C (according to the EA288 Self Study guide page 25. Our local weather is not nearly as cold as yours but I get full operating temp (200F or about 93C) within about 10 minutes of city driving.
I would look into this soon as a cold engine will burn more fuel and wear faster. You should be able to tell if the coolant is circulating by checking how warm the engine coolant radiator is and the associated hoses. It shouldn't be circulating through the radiator at 71C. Make sure you are checking the engine coolant radiator and not the charge air cooler radiator.

Then again maybe someone who lives in a similar climate will reply, maybe the engine just cannot produce enough heat at such cold temps, I really don't know about that.

bigb said:

The thermostat is a regular spring/wax element unit and starts to open at approx 87 C (according to the EA288 Self Study guide page 25. Our local weather is not nearly as cold as yours but I get full operating temp (200F or about 93C) within about 10 minutes of city driving.
I would look into this soon as a cold engine will burn more fuel and wear faster. You should be able to tell if the coolant is circulating by checking how warm the engine coolant radiator is and the associated hoses. It shouldn't be circulating through the radiator at 71C. Make sure you are checking the engine coolant radiator and not the charge air cooler radiator.

Then again maybe someone who lives in a similar climate will reply, maybe the engine just cannot produce enough heat at such cold temps, I really don't know about that.

Click to expand...

Thanks Bigb for the information.I was mistaken by the electrically controlled coolant pump.

Then it must be the thermostat as i can't remember coolant temp dipping that low last winter.But i will double check tomorrow morning by feeling the radiator hoses as you mentioned.

What's up with thermostats on the German diesels??

2-3 years ago i had to change thermostat on my X5 35D too while it was still under CPO warranty as dealer refused to replace it due to no ECU error codes and the temp was staying at 75 C.After the replacement, temp was rock solid staying at 88C and my fuel consumption reduced quite a bit and fewer regens.But in just 2-3 years it has started to loose its ability to control temp again.Its slowly creeping and my temp stays at around 82C.

Now looks like i will have to tackle this thermostat.

While it certainly could be a faulty thermostat, keep in mind that the diesel engine is very efficient (compared to a gas engine, a lot less of the energy in the fuel goes to waste heat - hence the better fuel economy), and thus, in cold weather, it takes some time to get up to operating temp.

If you're driving along in cold weather being very light on the accelerator pedal, I can see how (at -8C) it might take over half an hour to get up to operating temp.

I have a 7km uphill (from sea level to 150m) start to my highway drives, so I never see that problem. But just puttering around town, it does take a long time to heat up.

Do you have a grille block? It's not "super" cold here in Ohio that much, but on the "super cold for here" days (recent -20degF wind chill days), I can drive 15min on the highway before getting up to operating temp. That's with half the grille blocked AND the heater fan no higher than 3 lit up segments (SEL).

A Webasto or Frostheater would solve that slow warmup. Even at -20*f itll maintain 195* on the interstate so its just a slow warmup issue.

Thanks guys for the replies.Yes it could be just cold weather.
But i will still check the radiator hoses.Is the top hose on the radiator, input to the radiator from the engine?I am attaching the assembly illustration.I hope its the right one for the CRUA engine.

I don't have that answer but it is a pretty good bet, every engine I've ever seen runs the coolant from the top to the bottom.

Here it is from the EA288 study guide, coolant enters from the top during the operation phase and bypasses during the warm up phase.

warm up and operation

A cold weather data point.

Even after starting it in -20C not plugged in my car is over 80 degrees after a 25 minute drive.

Unless you're idling in traffic or coasting downhill your experience doesn't seem right.

I have the luxury of living in Wyoming. On subzero mornings, (F), when I leave work it takes about ten miles for the water temperature gauge to read about 200F. The oil temp will initially be in the 100-200F range after ten miles and will get to 195-220F after another ten miles.This was somewhat unaccepttable to me, so recently I plugged most of my front end with round foam and that has helped with these heat numbers coming in about 2 miles earlier. When I am able to find an available slot to plug in my frost heater at work the time to 200F water/175F oil is about 5 miles. BTW, 2 miles below 45mph from parking lot, 22 miles @ 80MPH on freeway followed by 3 miles cross town stop and go.