Coolant Temperature Fluctuations 1Z

Hello everyone!

Unfortunately, I'm experiencing the following problem...
It takes an incredibly long time (12km of city driving) before the engine even reaches the 80-degree mark. Then, I drive on the highway, and the temperature gauge just reaches the 90-degree mark and stays there. However, if I'm going uphill, the temperature immediately rises above 90 degrees, reaching something like 95 degrees.
When I then drive on a straight section of road again, it immediately swings back down.
If the outside temperature is above 17 degrees Celsius, it can even display over 90 degrees Celsius, even when driving in the city.

When I bought the car, the thermostat was faulty, so I replaced it.
Then everything returned to normal, but the temperature never reached 90 degrees Celsius, except when stuck in traffic.
I replaced the temperature sensor, and suddenly the temperature range shifted, but it didn't remain constant.

Is it normal for the car to take so long to reach its operating temperature?
The glow plugs for the auxiliary heater are working correctly (tested). But how do they actually work?
The thermostat is made by Wahler.
'Bought a temperature sensor and a parts fuzzier, color: YELLOW. The previous one was GREEN.'

'Any help is welcome!!'

Which vehicle?

For example, the Audi 80 doesn't have the well-known "plateau" function. The needle fluctuates constantly. It also takes me about 15 minutes for the car to warm up in sub-zero temperatures.

Where do you see a problem?

This is a Volkswagen Golf 3 TDI manufactured in August 1994.

The warming is not time-dependent.
If I let the car idle outside with an outside temperature of 5 degrees Celsius, it still won't warm up after 20 minutes; it's only at 50 degrees.

The problem is these fluctuations. Even when I'm driving faster than 130 km/h, the needle still moves past 90 degrees, just like when going uphill.

So, I'm worried when it gets warmer outside again, because the temperature inside almost constantly rises above 90 degrees.

The warm-up time is definitely time-dependent!
But of course, that's not all. It also depends on factors like load, speed, outside temperature, etc.
First, make sure you've installed the correct temperature sensor and that your control unit is displaying the correct value.
USE SEARCH. Ulf has described this type of testing procedure with 330 ohms very well.

Once you've checked all of this, you'll know whether the problem is with the thermostat or not. The temperature fluctuations you're experiencing suggest that it might be the thermostat.

Do you have any coating (reflective/metallic layer) inside the expansion tank?

G. Georg

You should have been able to find these links.

/viewtopic.php?p=51206&highlight=#51206

Okay, I'm ready. Please provide the German text you want me to translate.

Compare the temperature of the KI (instrument cluster) with the temperature reading from the EDC (engine control unit) using VAG-COM.
2. Check the thermostat. While the engine is warming up, stop several times and touch the lower radiator hose. As soon as the hose becomes warm, the thermostat is opening. It should not open until approximately 87°C (189°F).
3. If you feel like it, you can also remove the thermostat, place it in a pot of water, and slowly heat it up. Use a thermometer to determine the opening temperature.
If I remember correctly:
Starts to open at 87°C.
Erreicht max. Melting point: 107°C.
max. Hub 8mm.

You probably won't reach 107, but it should be enough for a review.

FlatEric wrote:

It takes an incredibly long time (12km in city traffic) before the engine even reaches the 80-degree mark. Then I drive on the highway, and the needle just reaches the 90-degree mark and stays there. Only when going uphill does the temperature increase, and the needle immediately goes above 90 degrees, to something like 95 degrees. If I then drive on a straight section of road again, it immediately swings back down.

This is likely because the thermostat is located at the cold water inlet, while the sensor (typically) is located at the hot water outlet of the engine.

Effect: Even with a completely constant intake temperature into the engine (at the thermostat), the heat generated at that moment (load-dependent!) is added to the reading displayed.

-> It's perfectly normal for it to get warmer when going uphill compared to being on flat ground (at roughly the same pace).

hello!
Thank you for your tips.
I cleaned the container a few weeks ago and replaced the refrigerant.
To replace the thermostat, I need to remove the servo pump. I'll buy an original thermostat from ***** and an original temperature sensor.
Unfortunately, I don't have a VAGCOM, so I'll try using that first.
Unfortunately, I installed generic, unbranded parts, and I'm not comfortable with that.
I once waited for the radiator fan to turn on, but it only kicks in well above 90 degrees. But that doesn't really matter on the highway, as the temperature also rises on inclines and at higher speeds.

I also replaced the thermostat in my car a week ago. Before that, it was only reaching about 77°C after driving for half an hour.
I bought one from the accessories section - it was from Waher, and wouldn't you know it, the one that was already installed was also from them. They might be the original equipment manufacturer.

Oh yeah: I don't recall the fan ever starting up. But I've never seen temperatures above 95°C. (The fan is working).
I should probably let it run on the stand during the summer.

It's strange... I know there are different thermostats, one from before 07-94 and one from after 07-94. Maybe the wrong one is installed. So, I'll have to use VAGCOM to check what the actual temperature is doing. There are no error messages yet (last checked).

The temperature gauge on my father's A61.9 TDI has never moved above 90 degrees.
uphill or downhill... nothing. My driving school car (4 years old) was also a TDI, but the needle never moved on that one either.

In my opinion, at an outside temperature of 3 degrees Celsius, the engine temperature shouldn't exceed 90 degrees Celsius even when driving above 140 km/h.
or?

FlatEric wrote:

It's funny...

I know that there are different types of thermostats.

FlatEric wrote:

Are you talking about the thermostat or the temperature sensor?

The temperature gauge on my father's A61.9 TDI has never moved above 90 degrees.}
Plateau function!!
=> Search function!!

Thermostat.

Oh, so the 1z didn't have that plateau function yet...
it explains a lot...

Quote:

Oh, so the 1z didn't have that plateau function yet...

I'm not sure if that statement is generally true. The plateau function is integrated into the AI system, and it's vehicle-dependent.


Oh yeah: I happened to have my old thermostat in my hand yesterday. It's an original part and it's made by Wahler. So, Wahler is (at least for me) an original equipment manufacturer.