Feb 22, 2012
This should be a sticky as it comes up nearly once a week.
Jay - when you change your thermostat would you be good enough to take a few pictures and do a write up? I can then link it into the DIY Guides sticky, and it will then help the next person who asks the same question, and will be karma for all the help you've received from this forum in the last couple of days.
I have some time tomorrow so if I remember I will take a few pics
I can do if you want but Stu seems eager to do it lol so il let him do it
here ya go this might assist in finding the stat
Do i need to flush and refill with new coolant if i need to change thermostat .. i just put new coolant on service 2 weeks back?
This diagram is for a 1.8T right ..? coz mines a 1.9 TDI
just saw on another forum and it says to remove alternator
get your hand behind it all, take all plastic off and move wires out the way ...
my spelling is poo ..wish i could just do it for you !!
i wished you could too lol try loooking at this
How to change thermostat on a4 1.9 tdi - FixYa
Right, this is from Elsawin AND Etka for a AVB engine. beyond this there is nothing more we can do for you.
The first round is definitely on you!
It's just behind the alternator, you don't have to remove the alternator to change it, did mine awhile back, 20mins to do.
The above guide is very good, can't get much cleaner then that.
Had mine done today too...
Although i didnt do it, i saw it being replaced/changed
It was done in under 30 mins and was straight forward
Remove the 2 bolts holding the plastic pipe onto the block and pull it towards you (carefully)
Fingers in, thermos out, new one in with new O ring
Bolt it back up and top up with fluids (pink stuff, think it G13 or G62 or something with a G)
No need to take the alternator off
Ok I just done my thermostat replacement on my 1.9tdi 130. Takes about 20 mins and thanks to all the above posters with their advice.
It's a very simple job and only involves removing 2 10mm bolts, no need to remove alternator or anything else (well apart from engine cover). You don't even need to drain the coolant, but you will lose a litre or so, so will have to top up at the end and also beware of hot coolant water, infact it's best to leave it for at least 1 hour as you will also have high coolant pressure when hot.
The images uploaded by Quattrojames were very useful in sourcing the thermostat housing. I've uploaded a terrible photo of the housing below, marked in red, and with the yellow dipstick pipe next to it for reference.
Using a 10mm socket with extension bar, I undone the two bolts. Took hold of the plastic pipe and pulled back enough to expose the thermostat and let some coolant drain. Then I removed the thermostat and o-ring. I replaced the new thermostat and o-ring by pushing it into the engine-block side as it sits in place much easier than trying to place it on the plastic pipe side. My thermostat kit came with a paper gasket but I didn't use this as the housing didn't have it as standard and it was also a pain to place it without damaging it with wet and greasy fingers..Hopefully I won't regret this decision..
I started the car and looked for leaks and topped of the water reserviour as necessary.
I haven't taken it out for a ride yet to report of any MPG changes, but if it still stays low (around 40mpg) then I'll be replacing the temp sensor.
Is jay still out there looking?
LoL im just seeing this now ... i got it done this morning .. lol
I lost all my coolant .. i took the stat out and coolant blasted out
Was a simple job to be honest .. thanks for all the helps guys
could not manage to put the temp sensor as i got the wrong one ... Green one with 4 pins, my ones black with 2 pins!
BTW .. still got a problem .. it goes to 90 Degrees now but when i switch my heating on .. it goes down to 70 degrees or less .. Whys that?
mine dose the same if iv not been driving for a good 30 mins or so as you are just pinching the engine heat
so your saying thats normal??
in the winter if you have not been driving long and it just hits 90 and you turn up the heater yes as the car has only just got hot so of course its going to cool the engine even in the summer if you have a over heating problem and you put the heater on full heat it will help to cool it
so your saying by turning the heating on makes the coolant temperature low and keeps the car cool and vice versa??
Not vice versa... Putting the aircon on doesn't warm the car up.....
If you think about it, if the coolant is circulating the car at 90c and then you turn the heating on, as the coolant passes through the heater matrix and the heat is taken from it then the coolant will cool. At this time of year, a diesel (which runs cooler than a petrol anyway) will loose the 'heat' in the coolant this way. I would expect to see the temperature drop when you turn the heater on, but then over time as the system compensates the temperature would increase.
But surely with climate control its set at 18c, 21c or whatever and it slowly warms as the engine temperature rises? Or do you drive along with the climate control off and then turn it on when the cars up to temperature?
wow this is really interesting .. learning something .. so air con on does not warm your car up properly .. ??
I put on my heating when i see the coolant temperature rises as i know il get instant heat .. is that bad?
do you no how you get hot air in the car jay ? the rad water gets hot this runs around the engine and there is a small rad in the car under the dashboard. the fan blows the heat from this witch at the same time cools the water passing through it before it goes back in to the engine to start all over again. so it will in the winter cool the engine down if it is not 100% on 90c so a 15 minute run would show 90c but only just so yes it will cool it off but say a 30 minute run will hit 90c but stay there no matter what. as it has had a good chance to heat up in the summer it will help to cool the engine if you have the heater on full and the heat up to max not alot but will help to cool it because of what i said above hope that makes seems as im not the best at wording things ;-)
Read again what I said about air-con, it was tongue in cheek. Air-con will not affect your engine temperature to any significant degree.
I keep my car at 18c all year round virtually. That way the heating and coolant temperature will equalise and warm up together, so you won't see the drop which is worrying you.
okay but when i choose the option to have feet on face, feet and windscreen .. i barely have heat coming from the face vents ..??
18c is too cold lol ... no ???
i think 24 is perfect
mate your hard work lol
I'd have the windows open at 24c!
You need to check the operation of the mechanism which diverts the air flow. See if you're getting airflow from all of the ducts. There are electric motors which send the air to where you want it. Its not uncommon for these to fail, but don't start panicking too much, it seems that you convince yourself your car has every fault we mention!
Never read a medical encyclopedia will you...!
LMAO ... true say hahah
Mine's always set at 18c, unless in winter when it's really cold I'll put it to 21c.
Hmm, even though thermostat change worked on mine and now sits at 90 degrees (and gets there quickly) my MPG is exactly the same: 41mpg based on DIS. I didn't change the temp sensor, I would have thought this might be the issue if it sends temp data to the ECU, but looking around on here it seems it just sends it to the temp gauge.
The temp sensor does send the temp to the ecu
What sort of driving do you do? The missus uses my car for work and its a 8 mile run some stop start some short 40's and a stretch of 60mph over two tanks I've had 41 and 46 mpg average of 43 its best to work out on a full tank from fill to fill and not guess or off the Dis
If you look at other threads most people are getting 40 to 48 ish
Does the temp sensor send data to both the ecu and gauge? If that's the case and my gauge is reading fine, then possibly the sender is ok?
41mpg was recorded mostly on the motorway and going easy on the throttle to try and get a good mpg reading. I'm also looking into EGR valves/VNT vanes to see if there are issues there (or are these only B5 specific?).
You need vagcom to verify that the sender is reading the temp right really
It could be a number of things affecting low mpg common ones are stat, temp sensor and maf
I wouldn't trust the dis though for a true reading if you can afford to fill it then fill it right up reset the trip drive for around 100 miles fill up again noting the miles and litres used and work out true mpg and work from there
If anyone tells you to unplug the maf sensor don't do it as it will just show up a code if you have to get it scanned
after 3 weeks of driving .. it does not reach 90 degrees anymore .. ?
The stat may have failed ie stuck open.There some cheap ones that can do this
I'll wake this thread up..
My TDI only reaches 90c when accelerating much.. As soon as I drive at constant speed, it returns to about 80c
Then some acceleration will get it back up to 90c but real quick back to 80ish.. Now when its cold (-7c) it stops at 70ish when driving normally.. But it Can still reach 90c(never above) with some +3000revs acc
Any problems with that?
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