Temp Sensor - no heat?

audifan

A2OC Donor
Coincidently I started my tdi today and it was left at idle. It took 50 minutes to get to 90 and that was heater off and correctly working thermostat and temp sensor. The first 40 minutes the gauge did not move and only in the last 10 minutes rose from 60-90.
 

Mr Angry

Member
Thanks for reassuring my doubt on what seems to be a successful 2nd attempt on this thermostat. I used 2 LTRs of OAT antifreeze from Halfrauds. I should've bought the 5 ltr @ £21 but only paid £7 odds for the 2 ltr due to a £5 discount code so all in it was under £20 to get both sensors done :)
 

audifan

A2OC Donor
Just pop back in a few days if still OK. Anything else you need help with or even a question just ask.
 

Mr Angry

Member
update...

everything seems to be running fine with no leaks etc... just out of curiosity though, how do you determine a faulty thermostat when comparing to new? the original Audi part spring is much stiffer than the replacement thermostats spring...is this normal or just the difference in quality?

thanks for your help guys :)
 

spike

Member
There are 2 main faults which can cause an engine to run cold.
First is the opening temperature. It's normally around 88 C and can be checked in a pan of water with a thermometer. As the water is heated the sealing disc should just lift off its seat at the stated temp
The other is the sealing disc does not fully close when cold. Sometimes it's debris trapped under the disc, Sometimes one of the 'bridge' legs legs cracks so the disc does not sit flat against the seat or it may be a faulty wax capsule - all easy to check on the traditional style TDi thermostat

Cheers Spike
 

audifan

A2OC Donor
By carefully heating it in water and using a thermometer to check the initial temperature that it starts to open and the temperature that it is fully open. Other than that you are looking for physical damage, debris stuck in the valve or anything else out of place.
Thermostat on the diesel starts to open at 87 and is fully open at 102 and has about 8mm movement

Checking thermostat
Heat removed thermostat in water bath.

Starts to open​
Fully open​
Opening travel​
approx. 87 °C​
approx. 102 °C​
at least 8 mm​
 

audifan

A2OC Donor
This also explains why the temp gauge appears to stick about 87 before jumping to 90. Conversely only a small amount of extra cooling or less heat produced will see the engine temp drop to 87 and close the thermostat. The rest of the system cools quickly and that is why you see the gauge dropping back quickly.
 

dj_efk

A2OC Donor
The mention of Circoli thermostats vs. genuine is interesting to me personally as Audrey has a genuine part fitted, whereas Akoya has a Circoli:

There is definitely a difference in warm-up behaviour between the two cars - Audrey warms up - purely going from the gauge - in a linear fashion, the needle does not pause on its way to 90, once there it does not drop away again unless you go down a very long hill off-throttle in very cold weather. Akoya on the other hand warms up to about 80-85 degrees on the gauge and the needle does pause there - if I’m using the car gently it will not move further for quite a while and heat will readily bleed off to a certain extent if the car hasn’t warmed up fully and you go down a smaller / medium sized hill off-throttle - due to the hills round here that’s not normally a problem however as I’m soon on throttle going up again, meaning the car does warm up almost as quick as Audrey overall.

My conclusion is: it’s worth paying extra for a genuine part - the TDI thermostats on our cars appear to be hard to manufacture to a high quality; as I’ve even had a duff genuine one that had failed out of the box (what a waste of money in garage labour that was!). My assumption is that even though Circoli thermostats tend to work as intended and be reliable, as an aftermarket part it is still not calibrated quite as finely as the genuine one is.

That said, it’s not really worth disturbing the system to replace a Circoli (or any other aftermarket) one if that’s what’s already fitted and it’s working - for me anyway.
 

Mr Angry

Member
Excellent replies....very interesting. I won't buy another aftermarket part again if this fails within a short period of time. I'm still not seeing the needle budge from its position with 20 mins of local driving and heat on HI but low setting. I am getting heat which is the most important part for me just now but something's niggling at me thinking that this part could be faulty or am I just being paranoid?

Just the thought of doing this job again is making my head hurt lol
 

audifan

A2OC Donor
No not paranoid, you would be surprised just how many parts are either DOA of fail very shortly afterwards. Hard to do but i have seen the thermostat fitted in the wrong way around before.
 

audifan

A2OC Donor
Re the heater settings. On the A2 the heater runs full bore hot from the coolant system. The temperature is regulated by changing the amount of outside air that passes over the matrix to cool the heater.
 
D

Deleted member 16918

Guest
Has anyone on this forum tried an electric water pump? It seems a popular thing to do on some 1.9tdi forums and it seems to me that it would mitigate the long warmup times and also get rid of the thermostat issues.
 

Bubonico

New Member
Hi,
Does anybody knows when the 1.4 AUA heats up to 90 Degrees?

I just bought an A2 from an Audi dealer and i did 40km and the needle stayed at 65 degress.

Today i had to go home from work to pick up a documents i forgot. On my way home the needle stayed at 65 degrees. I arrived home picked up the documents (10 minuts maximum) and then, when i started the car again the needle showed 90 and stayed like that all the way back to work.

The thermostat could be in open position, but i am not sure.

Is it normal to drive on the highway for 40 min. And the engine never get to 90 Degrees?

Thanks!!!
 

treblezero

A2OC Donor
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
Is there a page I can reference for the AMF, EGR, EU3, BHC etc.? I'm not familiar with these terms so this kind of post makes sense to me. Ta
 

Proghound

Admin Team
AMF, BHC are the two VAG engine codes for the 1.4TDI. The BHC was a minor update of the AMF using the same engine block and head.
EU3, EU4 are two successive historical emission standards for all new cars in Europe. We're now on EU6.
EGR = Exhaust Gas Recirculation, a system which makes the engine burn its exhaust gases again to improve emissions. It's more efficient/effective when the EGR valve is water-cooled, hence attaining EU4 on the BHC engine which employs this feature.
 

dj_efk

A2OC Donor
Hi,
Does anybody knows when the 1.4 AUA heats up to 90 Degrees?

I just bought an A2 from an Audi dealer and i did 40km and the needle stayed at 65 degress.

Today i had to go home from work to pick up a documents i forgot. On my way home the needle stayed at 65 degrees. I arrived home picked up the documents (10 minuts maximum) and then, when i started the car again the needle showed 90 and stayed like that all the way back to work.

The thermostat could be in open position, but i am not sure.

Is it normal to drive on the highway for 40 min. And the engine never get to 90 Degrees?

Thanks!!!
Short answer is no it’s not normal - either your gauge sensor (which is a twin circuit unit for both the gauge and the ECU) or your thermostat are faulty.
 

A2Z

A2OC Donor
Does anyone know the actual manufacturer of the 'genuine Audi' thermostats and temperature sensors/senders as Audi don't make their own parts and all are made and supplied by other manufacturers?

Would be nice to know rather than paying a premium for the same part
 

Mr Angry

Member
Update...

Not sure if this 3rd party temp sensor was the best option to try out :/ wether or not it's working properly, i'm not sure. I do get heat into the car but still takes some time. Does it matter if i have more anti-freeze in than the normal 50/50 mix? to be honest i ain't sure how much more stuff i put in when it started leaking first time around and just topped up when everything was sealed and not leaking.

Also, this has been the worst fuel consumption i've had since i filled it up 2 weeks ago with a return of 365miles which is way below my usual 400+ mpg :(

I'm gonna have to stick with it just now anyways as the bad weather is almost here and i've no time now!

Cheers
 
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