1.8T , Engine can't maintain normal operating temperature.... ?

[2stroke]

I have a problem, my 1.8T can't maintain normal operating temperature during normal winter temperatures.

I have changed the following parts 3 !!! times, but no difference.
* Thermostat
* Sensor G62
* Sensor G2

What could be wrong when the engine is unable to maintain normal operating temperature ?
( ....bad Thermostat you think, but since I have changed it 3 times I have ruled that out )
I have also logged the oil temperature with VCDS and I also think it is too low ( which also indicates that the cooling water in the oil cooler has too low temperature )
There are no error codes.
No leaks.


HELP !!

[B5carl]

From VWvortex

"If your heater doesn't blow hot air after a few minutes of driving then it's the tstat. If it does then it's the coolant temp sensor."

His solution was the coolant temperature sensor

[2stroke]

Overheating or won't reach operating temp?

Won't hold/reach normal operating temperature.
The engine runs too cold and can not maintain the correct normal temperature.

[B5carl]

Won't hold/reach normal operating temperature.
The engine runs too cold and can not maintain the correct normal temperature.

To verify that it's not reaching temp you should use a Lazer thermometer and point it at the block and radiator and match measurements with your interfacing tool

It has to be either the thermostat, or either one of the temp sensors. Also make sure you didn't install the thermostat backwards if thats even possible. Also go with OEM if you haven't already

[B5carl]

Do the same for the oil pan to verify that your oil temp sensor is also working properly

[old guy]

You need to post this in the A4 B8 forum. Your 1.8T is a 1.8 TSI EA888 Gen2 118 kw. This is very similar to the 2.0TFSI engine used in the A4 B8. The cooling system controls are very different than the 1.8T 5 valve engine found in the B6.

[2stroke]

You need to post this in the A4 B8 forum.
Your 1.8T is a 1.8 TSI EA888 Gen2 118 kw.
This is very similar to the 2.0TFSI engine used in the A4 B8.
The cooling system controls are very different than the 1.8T 5 valve engine found in the B6.

NO, I have a 1.8T ( 20 valve ) in my Audi A4.

[2stroke]

Make sure you didn't install the thermostat backwards if thats even possible.
Also go with OEM if you haven't already

It's not possible to mount the thermostat incorrectly as it is mounted together with a "Heater Element" inside.
You change this whole part as a unit.
( Look here also: https://www.audizine.com/forum/showt...at-Replacement )

Z2 .jpg

Z4 .jpg

Z3 .jpg

[B5carl]

Oo right this is the B6 section. I was referring to my B5 AWM 1.8t. I think you have the AMB which has the ECU controlled thermostat.

You should first verify actually temp with a Lazer thermometer.

[2stroke]

Ooo... right this is the B6 section.
I was referring to my B5 AWM 1.8T.
I think you have the AMB which has the ECU controlled thermostat.
You should first verify actually temp with a Lazer thermometer.

I have the "BEX" / "BFB" engine.
Yes the Thermostat is partly controlled by the ECU, since it has a Heater Element connected to it.
( This Heater Element can not be replaced separately as it is physically connected to the thermostat. )

I have a infrared laser thermometer, I will test and do some comparing readings with it.

[old guy]

NO, I have a 1.8T ( 20 valve ) in my Audi A4.

Sorry. I thought you had a EA888 1.8t Clicky click

The 20valve 1.8T has a mapped cooling system. That thing on the thermostat isn't a sensor. It is a heating element. The ECM uses it to adjust the block temperatures. Here is a thread that you may find useful. Pay particular attention to posts 14 and 22. It gives a pretty good explanation as to how it works and what measuring blocks you can use to troubleshoot the issue. Clicky click

[2stroke]

1. Sorry. I thought you had a EA888 1.8T
Clicky click

2. The 1.8T 20 Valve has a mapped cooling system.
That thing on the thermostat isn't a sensor.
It is a heating element.
The ECM uses it to adjust the block temperatures.
Here is a thread that you may find useful. Pay particular attention to posts 14 and 22.
It gives a pretty good explanation as to how it works and what measuring blocks you can use to troubleshoot the issue.
Clicky click

1. That is the car that my wife drive...

2. Interesting information.
I have my own VCDS ( But I'm a real rookie how to use it ! )
I will try to manage to log and save while I drive.

Quote:
Monitor blocks 130, 131 and 132.
* Block 130 will give you the engine outlet temperature and the radiator outlet temperature.
* Block 131 will give you engine output and engine output specified. The specified will be around 100° C. depending upon RPM.
* Block 132 will give you the radiator outlet temperature as well as the delta between the engine and radiator outlets and the thermostat heater duty cycle.

What you should see is that the block will heat up to around 100° C. while the radiator outlet will remain steady.
The delta will be significant. Once the engine outlet goes over 100° C. you will see the thermostat duty cycle start to increase and the lower radiator outlet temperature will increase.
The delta will decrease until you see the engine outlet drop below 100°c.
The duty cycle will decrease and the thermostat will close.

If the engine outlet temperature never reaches 100° C. and the duty cycle stays really low ( 3 %~5 % ) you need a new thermostat.
If the engine outlet is below 100° C. and the delta between the engine outlet and radiator outlet is low that would be another indication of a faulty t-stat.

- - - - - - - - - - - - - - - - - - - - - - - - -

This is gonna take a bit of 'splaining so I will do my best to see if I can make a little sense out of what you are looking at with your logs.

First order of business is to give a basic understanding of how a mapped thermostat operates.
The thermostat has a mechanical element that opens at a set temperature.
The actuator in the thermostat has an incorporated heating element that the ECM can use to "trick" the thermostat into thinking the coolant is hotter than it really is.
The ECM uses this feature to provide additional cooling when it feels it would be advantageous to the prevailing conditions.

The coolant temperature is measured at two points.
The rear CTS ( G62 ) measures the coolant temperature as it exits the block.
The lower radiator hose CTS ( G2 ) measures the temperature coming out of the radiator after it has been cooled.
As long as the thermostat is closed the temperature at the lower CTS will be low.
Considerably lower than the temperature leaving the block at the rear CTS.
When the thermostat opens you will see a rise in temperature at the lower CTS as the thermostat begins to allow the coolant to begin circulating through the radiator and into the block.
When the thermostat is closed the coolant completely bypasses the radiator and flows back through the thermostat housing via the lower coolant hard pipe and the last coolant drop line from the upper hard pipe return line into the thermostat housing.
When the coolant gets hot enough the thermostat opens up and the radiator circulation begins.
All this is controlled by the mechanical portion of the thermostat.
Looking at your logs I can see that your mechanical portion is controlling the exit temperature to around 93°c. Anything above that and the ECM starts to increase the duty cycle.

Now the fun part begins.
As long as there is no load on the engine the ECM is content to leave the thermostat alone and let it do its thing.
When this is occurring you will see a duty cycle of 3~4 %. Yours is set at 3.9%.
Whenever you increase the load on the engine the ECM recognizes that an increased load will result in increased block temperatures so to compensate the ECM increases the duty cycle to the thermostat.
This "tricks" the thermostat into thinking the coolant is hotter than it really is and consequently the thermostat begins to open.
This is quickly evidenced by the increase in temperature at the lower CTS as the coolant now begins to flow through the radiator into the block.
Now you will see the lower CTS temperature increase and the upper CTS temperature decrease.
As long as the increased engine load is present the ECM will keep the thermostat open.
Once the load decreases the ECM will leave the thermostat alone and let it do its thing.

With all that in mind you have to look at your engine load, your block exit temperature and your radiator exit temperature to see if your thermostat is operating correctly.
Yours appears to be reacting pretty much as expected with possibly a few incidences of partially sticking in the open position.
I'll give you an example:

In your first log take a look at the data between lines 2640 and 2760.
What you will see is that the heater duty cycle is essentially off.
That means the thermostat should be controlling the exit temperature to around 93° C.
But what you actually see is the block temperature dropping and the lower CTS increasing.
The only way this can occur is if the thermostat is open and at the recorded temperature it should not be open without a little help from the ECM duty cycle.
This doesn't come back into check until around line 2760 where the block temperature gets back to where it should be considering the engine load.

Granted, it isn't a dramatic case of a sticking thermostat but it just happens to be what you recorded in this particular logging session.
With all the parts you are getting ready to replace I believe you will take care of your problem.

[old guy]

Post up the logs and I will be happy to review them. The 1.8T mapped cooling system is a bit different then what you typically see. It was designed to allow the block to operate at fairly high temperatures for higher fuel efficiency at steady state driving but have the ability to reduce the temperatures when the engine load increases.

[2stroke]

The 1.8T 20 valve has a mapped cooling system.
That thing on the thermostat isn't a sensor.
It is a heating element.
The ECM uses it to adjust the block temperatures.

I have seen that these thermostats can be bought marked with 3 different temperatures:
* 100° C.
* 103° C.
* 105° C.

Does it matter which one I have in my engine ?
What will be the difference in practical terms ?

[2stroke]

Post up the logs and I will be happy to review them.
The 1.8T mapped cooling system is a bit different then what you typically see.

Thanks !

[old guy]

I have seen that these thermostats can be bought marked with 3 different temperatures:
* 100° C.
* 103° C.
* 105° C.

Does it matter which one I have in my engine ?
What will be the difference in practical terms ?

I was unaware that the 1.8T mapped thermostat had different options. I would go with the 100° C option. No need to run any hotter.

[old guy]

Something I should have mentioned. Before you log your cooling system in VCDS you need to scan for and clear any active cooling system DTC's.

For example: "P1296 Error in Mapped Cooling System". The ECM gives this code when the logged coolant temperatures are out of the expected range. The ECM knows something is wrong, but it can't pinpoint the exact issue. Consequently the ECM will take steps to prevent the engine from overheating. Stuff like turning on the cooling fans and running a high duty cycle on the thermostat heater. The high duty cycle forces the thermostat to open early, thus preventing the engine from getting to full operating temperature.

The ECM will maintain the protection protocols until the code is cleared. If the conditions persist after clearing the code it will again set another DTC.

[2stroke]

Something I should have mentioned.
Before you log your cooling system in VCDS you need to scan for and clear any active cooling system DTC's.

For example: "P1296 Error in Mapped Cooling System".
The ECM gives this code when the logged coolant temperatures are out of the expected range.
The ECM knows something is wrong, but it can't pinpoint the exact issue.
Consequently the ECM will take steps to prevent the engine from overheating.
Stuff like turning on the cooling fans and running a high duty cycle on the thermostat heater.
The high duty cycle forces the thermostat to open early, thus preventing the engine from getting to full operating temperature.

The ECM will maintain the protection protocols until the code is cleared.
If the conditions persist after clearing the code it will again set another DTC.

Is it enough to run a regular/general error code reading with VCDS to see error codes that include coolant temperature related errors ?
...Or do I have to do something else with VCDS to gain deeper insight into coolant temperature related errors ?


( ...As it is now, there are no error codes at all when I run a regular/general error code reading with VCDS. )

[old guy]

Yes, if you run the regular full VCDS scan it should pick up any open DTC's.