2017 1.4 TSI thermostat/water pump faulty?

[jakimpt]

Hello everyone

I'm an owner of a 2017 Leon 1.4 TSI 150cv and so far (48k) I'm satisfied overall with the car.

Though right now I'm facing an issue not with the car itself but with the thermostat housing.
One year ago I did myself the basic servicing, the oil and filters replacement.
I also did the coolant replacement from the G13 to the G12evo following a thread here about this work. Everything went fine, the filling with new coolant and the system bleeding (using hand press on tubes and a couple of driving after I had to top up the coolant level).

About 6 months after I did the oil/coolant level check again and had to top up the coolant as it was between min/max marks.

About 1 month ago I checked again the coolant level and noticed it was at min mark which made me inspect all coolant system tubing and thermostat housing as far as I could see. Found the thermostat housing was leaking below the water pump area.

I ordered this part on autodoc from Febi Bilstein brand and did the replacement about a week ago, also the oil/filter servicing at the same time, checked the maintenance manual for the guidelines regarding the replacement of thermostat/pump housing and I think I did everything correctly - the sequence torque while applying 30nm torque for belt tensioning, re-tubing, filling the system and bleeding just like I did last year.

Right now I'm facing a problem regarding the coolant temperature, on the subsequent trips I've noticed the temperature reaching 100c, 110c, even 116c, and then dropping gradually to 100c and hovering between 100c and 110c. I've also noticed in some trips that the temperature kept around 90c +- 3c, not even reaching 100c. All these values were read using OBD2 device.

I'm assuming this might be an intermittent issue with the thermostat.

What's your opinion? Can someone give me an insight about this problem?

Thanks in advance!

 

[jakimpt]

I should also add:

1. the cabin heater makes (really) hot air on max position.
2. I did a test today, the first drive of the day while reading live data with OBD device, after around 10min driving I noticed the coolant temperature rose to 114c and the radiator outlet temperature stayed around 22c with almost non-existent oscillation, which makes me think there might be a problem with the stat itself. What you think of this?

I'm leaving here the OBD live data report from the first driving today.

 

[jakimpt]

Nothing?

 

[nd-photo.nl]

-Is the thermostat opening and closing correctly? You can feel the feed hose to the radiator, that should be hot. And off course the return hose should be warm as well
-Is there a trickle of coolant from the small return pipe on the coolant reservoir? If not, there might be an issue with the waterpump
-Are the fans coming on when there is high coolant temp?
-If the thermostat and waterpump are ok and the fans are coming on, it might be a coolant temp sensor issue

 

[RUM4MO]

Just a comment related to this, as "radiator outlet temperature" has been mentioned, on the EA211 1.2TSI 110PS engine, there is no facility to measure the radiator outlet temperature, but the engine ECU has been configure to allow it to be monitored! This means that it is always reading an end of range figure, in the case of my wife's 2015 VW Polo 1.2TSI 110PS, that constant figure for actual radiator outlet temperature was -40C in mid summer! The specified radiator outlet temperature was 96C - in reality just sloppy code writing for that car/model/engine's ECU.

So, when you ever get back to re-checking your radiator outlet temperature - what was the value given for "radiator outlet temperature specified" - if it is something like 96C, then your "radiator outlet temperature actual" should be a lot higher than the 22C you quoted.

 

[jakimpt]

-Is the thermostat opening and closing correctly? You can feel the feed hose to the radiator, that should be hot. And off course the return hose should be warm as well
-Is there a trickle of coolant from the small return pipe on the coolant reservoir? If not, there might be an issue with the waterpump
-Are the fans coming on when there is high coolant temp?
-If the thermostat and waterpump are ok and the fans are coming on, it might be a coolant temp sensor issue

Thanks for your reply.

1. At least I think it is opening because I can feel the radiator inlet tube really hot (top left aft looking forward), but it might be opening too late/small flow of what it should because looking at the graphs the coolant temp usually reaches 115ºC on each ride and oscillates between 100/110ºC - OBD live reading.
2. If the return pipe is the small one at the top inboard side of the reservoir, yes I can see a bit of coolant hanging there.
3. Yep, they start to rotate when the coolant temp starts to rise, they even reached 90% speed when reading from OBD.
4. But before replacing the housing for the new one, I have not experienced a rise of temperature above 90 ºC on the dashboard, which makes me discard a sensor problem. I have confirmed a maximum OBD reading of 111 ºC is equivalent to 90 ºC on dashboard, at 98 ºC on dashboard is 112 ºC on the OBD, and it goes.

I have attached four OBD recordings.
The 1st was the first ride of the day, cold start.
The 2nd, the car was stopped for 1 hour before start the ride and it kind of behaved really differently from other rides, as you can see the temperature only reached 94 ºC (idle) and oscillated around 90 ºC while driving (50-120kmh speeds).
The 3rd, was stopped for 15min before starting again.
The 4th, was stopped for 3 hours.

 

[jakimpt]

Just a comment related to this, as "radiator outlet temperature" has been mentioned, on the EA211 1.2TSI 110PS engine, there is no facility to measure the radiator outlet temperature, but the engine ECU has been configure to allow it to be monitored! This means that it is always reading an end of range figure, in the case of my wife's 2015 VW Polo 1.2TSI 110PS, that constant figure for actual radiator outlet temperature was -40C in mid summer! The specified radiator outlet temperature was 96C - in reality just sloppy code writing for that car/model/engine's ECU.

So, when you ever get back to re-checking your radiator outlet temperature - what was the value given for "radiator outlet temperature specified" - if it is something like 96C, then your "radiator outlet temperature actual" should be a lot higher than the 22C you quoted.

Thanks for the reply.

I have uploaded four new images with OBD recordings related to four straight rides I did on Friday with the car. You can see the radiator outlet temp was oscillating on each ride. Though I can confirm there is a sensor right after the radiator outlet port at bottom left side (aft lookin forward) - the SEAT maintenance manual also shows it. So I guess the readings must be real.
Thanks

 

[nd-photo.nl]

The coolant system seems to be doing its work (to some degree); whenever the cooling starts, the temps at the radiator outlet starts to rise and the coolant temps drop.

[edit]
Or are you running a "hotter" thermostat

 

[jakimpt]

The coolant system seems to be doing its work (to some degree); whenever the cooling starts, the temps at the radiator outlet starts to rise and the coolant temps drop.

[edit]
Or are you running a "hotter" thermostat

Yes I agree but at the same time I think the radiator outlet temp is rising slowly even when the coolant is hot. Is it even normal the engine to get to ~116ºC? Can't get that into my mind.

Also thought of that, it may be hotter idk?
I've checked the manual and found this info - the small circuit stat should open at 105ºC and the large circuit at 87ºC. The new part I installed from Febi the small circuit stat opens at 97ºC (which is marked on the body) but I don't know what's the value for the large circuit stat because it's inside the housing

 

[jakimpt]

I've been confirmed by Febi Bilstein support the information regarding the opening temperatures of the stat.

"The thermostat integrated into this housing features a two-stage opening characteristic:

• First opening at approximately 87°C
• Second opening at approximately 97°C"

On the other side, the maintenance manual from the car says 87° first opening and 105° second opening.
Will this discrepancy make the coolant system work differently?

 

[nd-photo.nl]

Maybe the radiator is clogged/plugged up?

 

[jakimpt]

Maybe the radiator is clogged/plugged up?

How is that possible if the old coolant was perfectly pink clear when drained before replacing the housing, even before the replacement the behaviour was not the same as it is right now.

 

[nd-photo.nl]

You tell me, I'm just thinking out loud

 

[jakimpt]

You tell me, I'm just thinking out loud

I get it.
Well, I think I'm discarding a radiator issue.
Could be an issue with the temperature sensor but my bets are going to a defective stat/pump housing or anything to do with it (differently opening temperatures compared to original part). It's my 6th sense telling me that.

Another two logs here from two trips I did an hour ago. Something doesn't feel right to me..

 

[nd-photo.nl]

Follow your gut feeling

 

[SuperV8]

Did your new thermostat housing also come with new thermostats?
What exactly did you replace?
My 'feeling' would be either an airlock (as you didn't vacuum fill the coolant) or thermostat.

 

[jakimpt]

Did your new thermostat housing also come with new thermostats?

What exactly did you replace?

My 'feeling' would be either an airlock (as you didn't vacuum fill the coolant) or thermostat.

Thanks for your reply.

I'm assuming it came with both thermostats yes, because it's a "all in one package". At least I can see the #2 stat, which has engraved the "97°C" marking, as for the opening temperature. The inner stat #1 I guess it is also in place.

I replaced this all in one part which includes both stats and water pump, plus the toothed belt for the pump. Photo attached.

Indeed the system was not vacuum filled! Though shouldn't any air lock be automatically gone by now? After some quite rides already made.

Interesting to know is that a year and half ago I also did the coolant exchange along with oil/filter servicing, and put some fresh G12evo diluted 2:3 and applied the same manual bleeding method (read here on another thread) as I did now after replacing this housing and never had this kind of issues with temperature (on the dashboard coolant temp was always at 90°C, as I always had this view selected on dashboard).

Unfortunately my bets are going to a defective stat

Radiator clogged or faulty temp sensor, from one day to another? Don't fit on my mind if you know what I mean.

Thanks

 

[SuperV8]

Thanks for your reply.

I'm assuming it came with both thermostats yes, because it's a "all in one package". At least I can see the #2 stat, which has engraved the "97°C" marking, as for the opening temperature. The inner stat #1 I guess it is also in place.

I replaced this all in one part which includes both stats and water pump, plus the toothed belt for the pump. Photo attached.

Indeed the system was not vacuum filled! Though shouldn't any air lock be automatically gone by now? After some quite rides already made.

Interesting to know is that a year and half ago I also did the coolant exchange along with oil/filter servicing, and put some fresh G12evo diluted 2:3 and applied the same manual bleeding method (read here on another thread) as I did now after replacing this housing and never had this kind of issues with temperature (on the dashboard coolant temp was always at 90°C, as I always had this view selected on dashboard).

Unfortunately my bets are going to a defective stat

Radiator clogged or faulty temp sensor, from one day to another? Don't fit on my mind if you know what I mean.

Thanks

Just dropping the coolant, and filling up again does not have the same possibility of trapping as much air as actually pulling of the thermostat housing/pump, and fitting an empty housing. These are very complicated cooling systems with multiple circuits, one way valves and pumps.

Of course a faulty new thermostat is 'possible' - but for me I would say you have more chance/risk of trapped air causing your problems than a faulty new stat.

Trapped air could cause your symptoms as well as a stat, as it can prevent the pump from properly pumping due to cavitation, restricting coolant flow!

A vacuum filling kit isn't expensive - if you don't have a compressor for the venturi, you could probably rig up some hand operated vacuum pump.

You can test your stat opening/closing with some hot water to determine if it is the new stat which is faulty.

 

[XPtuning]

The coolant pump is belt driven, are you sure the pump is turning?
You're sure the thermostats are installed in the correct way? The temperature sensing cylinder(wax container)piece mounted at the hot side...did the thermostat and cover fit easily or did it require some extra force?

 

[jakimpt]

The coolant pump is belt driven, are you sure the pump is turning?
You're sure the thermostats are installed in the correct way? The temperature sensing cylinder(wax container)piece mounted at the hot side...did the thermostat and cover fit easily or did it require some extra force?

Thanks for the reply.

Not sure because I've installed the small cover before installing everything else. Will try to check that before doing any other thing!

I haven't changed the stats, it's a all in one package with both stats and pump.