Temp Sensor - no heat?

Mr Angry

Member
Hi Guys,

I now this has been covered a million times, however, can someone tell me how easy it is to replace the temp sensor, which i'm assuming is at the back of the engine block (read from another post but not sure where the exact location is) can i use the part i've pasted with link? and should i replace the other sensor located at the bottom of the radiator? are the sensors both the same or are they totally different?

The problem i'm having just now is that the gauge does not move when running idle, so no heat at all. As my wife doesn't drive the monster bus Alhambra and is driving my car now, i can't give a proper description but she has said it works sometimes :/ i need this fixed before the cold weather arrives :)


Cheers
 

audifan

A2OC Donor
That part is indeed the coolant temp sensor. The one in the lower hose is different and probably not an issue. If it was me I would replace both the thermostat and the coolant temp sensor with genuine ones from an Audi dealership.
not too difficult to change the temp sensor just tie some string around the retaining clip to stop you dropping it and make sure the old O ring is removed before fitting the new O ring and sensor.
 

Proghound

Admin Team
If it's a TDI, the engine itself produces next to no heat at idle. Hence the Webasto on the earlier cars and the electric cabin heater element on later ones to provide warmth. However by design, the Webasto won't do anything if it's above 7.5°C on the external temp readout, and that can still leave quite a gap between desired and delivered levels of warmth on autumnal mornings - even more so if it's colder and not working :p. If the EGR is unplugged (AMF) or mapped out (any TDI) this won't be helping the engine to warm up either, but that's not the main issue.

If the problem is a lack of heat, the gauge reading supplied by the coolant temp sensor may also be wrong, but replacing that isn't going to generate any heat. I'd be looking at the thermostat - a failed 'stat stuck open will never allow the engine to warm up properly, even with Webasto input. The same applies (possibly to a lesser extent) if it's a petrol engine. As Graham says, for preference you'd want to replace both the 'stat and the temp sensor, using genuine Audi ones.
 

RAB

Technical Specialist 1.2 TDI
If the EGR is unplugged (AMF) or mapped out (any TDI) this won't be helping the engine to warm up either, but that's not the main issue.
This doesn't apply to an AMF because the EGR is not coolant cooled, unlike a BHC. That's the main reason why a BHC is EU4 and an AMF is EU3 and why the BHC replaced the AMF.

RAB
 

LK79

Member
I might have the same issue, car never seems to warm up, anyone know the audi part numbers for the thermostat and Coolant temp sensor ?
 

audifan

A2OC Donor

044 121 113 VAG Thermostat, coolant​


059 919 501 A VAG Sensor, coolant temperature​



 

Robin_Cox

Member
Just a note that I felt is worth adding. For those without much time, the critical passages are here **

I should stress that I am a real believer in Febi parts and use them for most things. I had a coolant sensor 'open to earth, intermittent' fault on my AMF for a while - not the dashboard feed which was fine, but evidently the ECU feed was sometimes giving the ECU an erratic signal so possibly affecting fuel economy slightly. Bought one of the Amazon link ones in several months ago with overnight delivery at the usual decent price. Thermostat was changed at last year's MOT and made a difference on indicated warm up so clearly was also lazy previously.

Decided to swap the sensor in a few days ago. Whipped off the fibreboard cover over the engine and disconnected / swung the boost pipe up and out of the way. Found that at some point in the past the wee plate that is 10mm-bolted onto the engine with sensor loom attached that you need to remove to access the sensor was not there, so I had a clear view of the sensor and the sensor clip holding it in place - one step in the process eliminated. The light was also near-perfect to do this job - direct sunlight from over my right shoulder.

Removed the sensor clip with my 90-degree pliers. For practise I then clicked it back in to get the angle, then unclicked it again a couple of times to make sure - easily possible with fingers for once (compared to my BHC). Then wiggled the sensor gently until I could back it out of the o-ring. With the expansion tank lid and bleed valve closed, the pipe from the radiator bleed valve to the sensor housing drained some coolant out via the sensor port but that was it. Removed the old o-ring. Undid the sensor connector (it was rotated at an angle when in situ that was not permissive to undo the clip), and removed the old sensor - Audi part number stamp on it with some copper oxide stains at the interface with the o-ring suggesting it may well have been original or near-original. Wetted the new o-ring with dribble of coolant, put it on the sensor and slid the sensor into place. After a couple of goes I got it to seat fully, then I went to use the new clip that was supplied by Febi.

** This is the point where I encountered an unexpected issue. Using the same approach as with the old clip 2 minutes previously, I rotated it into place and then tried to push it home - and found that the leg at the back of the clip (out of sight) wasn't locating into the slot and instead was twisting when the leg 'on this side' was entering the slot fine. Lifted it out, straightened it up and tried again. After around 3 goes at this (bearing in mind I've done it before, my access was good, the lighting was good and I'd just practised it) I realised that there was something different about the clip in the way it felt in my fingers. Comparing the new clip with the original side by side, the original is exactly the same shape - but from the side, the new clip was a fraction of a mm slimmer - and consequently also bendier.
I then re-used the original clip which went in first time and clicked home securely. Topped up and bled the coolant (large amount of bubbles out of the bleed valve atop the radiator as the new coolant went in). Put everything back together, ignition on, cleared the sensor fault - and it eliminated for the first time - ran the engine for a few minutes with the cap off to drive any more bubbles out, final top up to the line and then put the bonnet on. Test drive was drip-free, so I am satisfied that it is job done. Will keep an eye on fuel although with winter tyres swapped the same day and colder weather coming I doubt I'll see anything dramatic.

** So the message is - keep hold of the original clip when you remove it. If the new clip (from whichever source) is slightly undersized, it would probably be a good idea to re-use the original or another of equivalent 'thick' spec. Weirdly I don't remember this being a problem when I did my first sensor replacement, so whether there has been some batch to batch variation at Febi is unclear.

part number for the clip is - 032121142 (20mm coolant sensor clip) - whether Crewe Audi do these at a sensible price would be worth asking.
 
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Mr Angry

Member
I managed to replace the sensor in the dark tonight with a torch however, i couldn't get the o ring out :( I did try and feel about for the o ring but couldn't feel it what so ever and with it peeing down outside i was starting to lose my patience. i hope this will be ok going forward with the old one :/

I have done tougher jobs that are easier than this sensor replacement on the A2, personally i thought this was a pig of a job. I guess having the correct tools make things easier but the lack of space and light made this frustrating.

@robin, i know exactly what you mean with the plastic clip missing the groove on the inside track! it was bending kind of outwards while the other side was in place. I did manage to get it in but what a fiddly job that is without right angled pliers!

I will recheck tomorrow once i get some G13 coolant from Halfrauds tomorrow as i lost a lot of coolant in the process. I assumed that OAT G13 concentrate would be ok to use on the A2... i guess not! it is showing that i must use Xstream G40 coolant Si-Oat instead of OAT when i entered my Reg Number, can someone confirm this?

If this doesn't resolve my issue then it's onto the Thermostat next.

Cheers
 
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audifan

A2OC Donor
Stick with G12, G12+, G12++ or G13. As long as the sensor is a good fit in the old o ring and there is now not 2 o rings in there should be OK. Did the old o ring come out with the old sensor.
 

Mr Angry

Member
No o ring came out with old sensor so i assume it's still in there or if it fell out without me knowing, if it has then i'm totally gubbed because i lost the new o ring as it fell into the engine bay and looks to be lost :( if it leaks when i refill tomorrow then i will need to source a new o ring for this.

Audifan when you say stick with G12 and upwards does this mean the OAT is ok to use instead of the Si-OAT???

thanks
 

audifan

A2OC Donor
G12-G13 is OAT. Can you wiggle the temp sensor now it is fitted? If not then good chance the O ring is present. you will certainly find out as you refill the system.

G12-G13 is still what is specified by Audi and indeed G13 is still in new cars today.
 

Mr Angry

Member
Will let you guys know tomorrow when i start the refill lol

I'm currently reading Pinkythelabrats thread from earlier this year ROFL!!!!

Grrrrr
 

Mr Angry

Member
So I took my car for a drive after filling it up with coolant. Temp eventually reached 90 Deg but as soon as I turned heating on, hi setting full blast, it started to slowly creep down to 60 deg. Does this mean I need to change thermostat now?

The heating is working and was probably like this before but it's only just warm when the heating is on. The only way it feels warmer is if I have heating off then let the temp reach 90 Deg then turn back on, which feels a lot warmer before it starts to cool off and drop down to 60 Deg.

Cheers
 

audifan

A2OC Donor
Yes certainly worth replacing the thermostat for a genuine one. In these sort of outside temperatures and slow traffic the engine does cool down more so the thermostat will be opening and closing to try to keep the engine temperature up. you could be driving at 70 on the motorway and come into slow traffic say for roadworks and the temperature will drop off.
 

Mr Angry

Member
Replaced thermostat and had to use the old o ring on that too. Put everything back together and it's leaking, it must be the oring not seated in properly, what a pain in the back side this is. I can't get to the underside of the black plastic part where the 2 bolts go in. Do I need to strip off more stuff to get into this?

Arghh!!!
 

Mr Angry

Member
Update...

I redone the whole process again and i think i might've struck it lucky for 2nd time, fingers crossed :) i did drive it for about 5 to 10 mins but the needle didn't move from 60 deg :/ is it because i topped up with fresh water and coolant? I bought the circoli thermostat from euro parts having read another post where depronman said this was a good replacement.

Not a job i would like to repeat in all honesty... now back to the monster bus alhambra :D

Thanks for all your help guys :)
 

audifan

A2OC Donor
hopefully you are leak free now. Keep an eye on the coolant level over the next 6-8 trips just to make sure no further issues.
 

Robin_Cox

Member
I've used two of the Circoli thermostats on my cars in the last 5 years independently of Paul (depronman)'s advice although subsequently found that we'd done the same. Both have been absolutely fine, although I am aware that not everyone has been as positive about them.

Time to warm up is very dependent on use levels, outdoor temperature and so on. In anything except summer conditions my Tdis take about 12 minutes at gentle commuting speeds and throttle-use levels to stir off the 60/min mark; in properly cold conditions I can arrive at work (14 minutes) before the needle stirs (although the internal temperature feed will have reached 58 or so by then). Conversely, when I am heading south and almost immediately onto the A90 at 60+ mph, the car will be up to 90 within 5 or 6 minutes or less depending on ambient temperatures.

When I first had the same car with the obviously knackered thermostat, the needle would remain stubbornly fixed to the 60 mark even at motorway speeds until you hit traffic whereupon the lack of airflow meant that the temperature would rapidly go up to 90. As soon as moving again the temperature would ebb away just as rapidly (this was how I diagnosed the need for a new thermostat). The coolant sensor was also intermittent - but on the dashboard feed - so once at 90, you could hit a road joint and have the dial drop back to 60 in a flash, to reappear at 90 a few minutes later without warning. Coupled with the thermostat, I had no idea what temperature the engine was for the first 6 months I had the car!
 
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