FR not getting up to temperature

Highlander

Active Member
Mar 16, 2016
18
8
So I've had this problem for a few months, where my Leon FR 184 DSG (44K miles, FSSH) doesn't get up to normal running temperature of 90 degC. I put it to a dealer yesterday, and they said no fault codes logged, and it got up to 90 degC when they ran it in the workshop.

So when I collected it, it was still hot from the workshop, and as I drove off though the evening stop-start traffic , it continued to read a normal 90 degC. As soon as I started moving freely, the temperature rapidly dropped to between 60 and 65 degC - even as I punted it up a steep Motorway hill, where you'd expect it to warm up. So that suggests (to me) it's an "airflow" thing - it gets hot when running stationary, but as soon as moving, the temperature drops off.

I tested that this morning - I took it for a run of a distance where it should have warmed up to 90 degC. But it remained at 60 - 65. When I parked up, I sat stationary, with the engine running at 2500rpm - 3000rpm for 5 or 10 minutes, and the temperature climbed up to 90. I then drove off, and within a mile, the temperature had fallen to 60. So there's definitely something going on where the temperature can't get up to normal when the car is moving. Have I lost a piece of plastic cowling that means there's too much airflow to the engine, maybe? I don't know.

I suppose the only other thing to try would be to go for a drive, holding the car in low gear and high revs - see if it's related to load?

Has anyone else experienced this? I don't want to end up having to get a new Cat or DPF, due to running it for miles not at proper working temperature.
 

Highlander

Active Member
Mar 16, 2016
18
8
I don't know - how would I tell if it's stuck open or not? And would that show as the "gets hot only when it's idling at standstill - but not on the move" symptom? If the thermostat is open, does the temperature never rise above 60 degC?

Thanks

H
 

BoomerBoom

Active Member
Jun 1, 2018
422
142
A stuck thermostat means the engine will take an age to reach operating temperature, if at all, especially while moving in cooler weather. When stationary it's less of a problem as the heat gets trapped inside the car.

Diesels in particular take a long time to heat up in cold weather, which is why they often have auxiliary heaters fitted.
 

Highlander

Active Member
Mar 16, 2016
18
8
A stuck thermostat means the engine will take an age to reach operating temperature, if at all, especially while moving in cooler weather. When stationary it's less of a problem as the heat gets trapped inside the car.

Diesels in particular take a long time to heat up in cold weather, which is why they often have auxiliary heaters fitted.
Thanks Boomer - that actually makes perfect sense. The water pump and cambelt were replaced a few months before I noticed the problem - maybe the wrong thermostat fitted? (I can't pin exact timing down, as - due to covid - my g/f was using the car exclusively for 3 months after... and ..... get this ..... she didn't even know the car had a temperature gague! We can laugh - I can't crochet worth a f***!!!)
 
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martin j.

Active Member
Feb 11, 2007
1,213
391
Fife
If the thermostat is stuck open the radhoses will get warm from the start up as the open thermostat is not holding the water back ? Start the car and while it’srunning Check the hose from the stat to the rad and see if it heats up gently or suddenly heats when the stat opens, I’ve noticed that when the temp is displayed on the dash it will rise steadily towards 90 but fall back a bit as the stat open opens allowing cold water to mix then rise to normal again.
 

Big Col

Active Member
Nov 5, 2013
578
69
North Ayrshire
ditch the dealer and find a decent local VW group specialist. This shows how badly many dealers work, plug in computer, no fault code = haven't got a clue

traditionally it does sound like a stuck thermostat - however it's many years since I did anything like this. I'm sure I read somewhere these engines have multiple cooling circuits so it may not be as straight forward as when I changed a thermostat on a Vauxhall Nova :):cool:
 

BigJase88

Jase
Apr 20, 2008
2,646
499
Dumfries & Galloway
Yeah as above stuck open thermostat.

new thermostat required.

some dealerships are beyond crap

if the car doesn’t produce a code they are clueless, they are robots not mechanics, however dealers call them technicians cause that makes them sound smart and they can charge £70 an hour labour for a technician robot.
 
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Brian Gordon-Stables

Active Member
Jan 16, 2020
252
81
Leicestershire, UK
If you had a cambelt/pump change, your thermostat would not have been changed as it's in a different location.

The thermostat is under the charge cooler and is an *rse to get to.

Due to overheating issues, I had mine done recently and also changed the thermostat housing (they are plastic and prone to cracking/leaking). Also had water pump and cambelt done at same time. It turned out the pump was faulty (known issue with electronic pumps in CUPA and CUNA engine codes - they now offer an alternative pump without the electronic part).

Although you've got a new water pump, it may not be working properly.

Also consider the coolant temp sender unit in the engine block .They are also known to fail. I've also had mine replaced.

I got one of these and checked all pipes etc to see which ones were hot or not to help understand the problem.


The car has 3 coolant circuits and whilst warming up the radiator isn't even in use. It's designed to make the car warm up quicker and meet emmission targets. Due to my pump issue mine was stone cold, even when overeheating.

The fact that your car is fluctuating suggests thermostat. Might be the best place to start. Just be aware that it's not a 5 minute job.
 

Highlander

Active Member
Mar 16, 2016
18
8
Glad its fixed - but £411 for a new thermostat :oops:
Tell me about it. The mechanic basically repeated what Brian's said ... with additional "colourful" language.
Sigh ..... when I used to do my own maintenance 40 years ago on V4 Saabs, a thermostat was something you bought from Halfords for a fiver, and was part of the radiator expansion tank cap ..... took 30 seconds to swap out, and that included a fag-break!!!!!
 

Yern

Active Member
Apr 25, 2019
336
175
Tell me about it. The mechanic basically repeated what Brian's said ... with additional "colourful" language.
Sigh ..... when I used to do my own maintenance 40 years ago on V4 Saabs, a thermostat was something you bought from Halfords for a fiver, and was part of the radiator expansion tank cap ..... took 30 seconds to swap out, and that included a fag-break!!!!!
Remember these... 1602719224562.png
 

SuperV8

Active Member
May 30, 2019
44
18
Tell me about it. The mechanic basically repeated what Brian's said ... with additional "colourful" language.
Sigh ..... when I used to do my own maintenance 40 years ago on V4 Saabs, a thermostat was something you bought from Halfords for a fiver, and was part of the radiator expansion tank cap ..... took 30 seconds to swap out, and that included a fag-break!!!!!
I think i'm just not accustomed to pay (tight-ass) anyone for doing car/home maintenance/improvements. My £ estimation is 20 years out of date! and i'm often left thinking 'how-much!' and that i'm in the wrong job as I could be doing that :oops: ; quotes friends have had for new bathrooms for example is another one - thousands! for just a new suite and some tiling!
I'm lucky I have a 'small' drive and tools to do my own car maintenance/repairs - in fact I wouldn't even know who to turn to as my only experience of garages is negative often having to fix friends and family's cars who have paid 'hundreds' for work to have to re-do that work!
Several cam belts timed incorrectly
Diesel pump issue - the 'specialist installed new fuel filter without removing existing seal so was installed with 2 orings! and sucked air and also saying it needed new pump and injectors! when it was just a simple £20 sensor.
Diesel injector seals -
etc..
Following this thread I'm looking at changing my thermostat just as a precaution - while i'm doing cam belt/water pump/coolant flush - and it looks like it still uses a simple wax type stat -
1602759949438.png

1602760062495.png
 
Last edited:

Brian Gordon-Stables

Active Member
Jan 16, 2020
252
81
Leicestershire, UK
I think i'm just not accustomed to pay (tight-ass) anyone for doing car/home maintenance/improvements. My £ estimation is 20 years out of date! and i'm often left thinking 'how-much!' and that i'm in the wrong job as I could be doing that :oops: ; quotes friends have had for new bathrooms for example is another one - thousands! for just a new suite and some tiling!
I'm lucky I have a 'small' drive and tools to do my own car maintenance/repairs - in fact I wouldn't even know who to turn to as my only experience of garages is negative often having to fix friends and family's cars who have paid 'hundreds' for work to have to re-do that work!
Several cam belts timed incorrectly
Diesel pump issue - the 'specialist installed new fuel filter without removing existing seal so was installed with 2 orings! and sucked air and also saying it needed new pump and injectors! when it was just a simple £20 sensor.
Diesel injector seals -
etc..
Following this thread I'm looking at changing my thermostat just as a precaution - while i'm doing cam belt/water pump/coolant flush - and it looks like it still uses a simple wax type stat -
View attachment 19170
View attachment 19171
A couple of things to bear in mind.

There are at least 2 different types of thermostat housing and therefore type of thermostat for that engine. When my mechanic checked with TPS, they said remove the old one and check. They couldn't tell from their spec sheets.

1602777538763.png



The thermostat (and housing) are nowhere near the water pump and cam belt and aren't really part of that procedure. If you are just changing the thermostat, you might be okay if you can access it. If you change the thermostat housing, that's where the fun begins due to very limited access and the need for a stiff drink or 3.

The basic principles of the thermostat are quite simple. Changing it, maybe not quite so simple.
 

Cuprabenwytm

Active Member
Jun 17, 2020
23
5
My old audi a1 2.0 tdi did this, does it use coolant? Check the footwell as mine ended up having a exploded matrix, fixed the matrix filled it up and it was good till a sold it


Sent from my MRD-LX1 using Tapatalk
 

SuperV8

Active Member
May 30, 2019
44
18
A couple of things to bear in mind.

There are at least 2 different types of thermostat housing and therefore type of thermostat for that engine. When my mechanic checked with TPS, they said remove the old one and check. They couldn't tell from their spec sheets.

View attachment 19174


The thermostat (and housing) are nowhere near the water pump and cam belt and aren't really part of that procedure. If you are just changing the thermostat, you might be okay if you can access it. If you change the thermostat housing, that's where the fun begins due to very limited access and the need for a stiff drink or 3.

The basic principles of the thermostat are quite simple. Changing it, maybe not quite so simple.
Thanks, yes good points - I did notice following posting this there are two versions of thermostat and my part catalogue with VIN lookup usually lists exactly the correct part but it still offered two versions JOOP 04L121113C or GEIGER 04L121113D - looking at my engine the housing I can see is the one linked to the more unusual plastic thermostat design you posted a pic of which is the JOOP version 1.
Mine is the twist to remove version 1 vs the unbolt to remove version 2.
Remove air filter housing,
Drop out coolant (which will already be done)
Remove rad cowl,
Remove couple of bolts from air pipe,
Release catch and turn coupling to remove stat - which seems simple enough! (famous last words!)
1602841649569.png

I agree removing the entire housing would be much more involved - but kinda pointless if you are just replacing the stat.
I thought while I had the coolant dropped out I would change the stat as a precaution/preventative maintenance, my Audi 1.9 stat failed around 100k and with the OP stat failing at 44k for a £20 part I will have a go. Also with you're previous comments about finding silicates in the thermostat it will help me to flush it out more thoroughly.
 
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