Temperature gauge question

I'm going to try bleeding the system, it's the one thing I haven't actually tried. I've found the bleed valve next to the upper radiator feed pipe, I'll run the car up for a few minutes and give it a go. I haven't got a Webasto sadly, stangely it's one thing I really miss from the old car.
 
Silverpig said:
I'm going to try bleeding the system, it's the one thing I haven't actually tried. I've found the bleed valve next to the upper radiator feed pipe, I'll run the car up for a few minutes and give it a go. I haven't got a Webasto sadly, stangely it's one thing I really miss from the old car.
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How do you do this (keeping it simple)? The Audi Workshop Manual link that @Techno posted is for refilling the system which presumably is a whole lot more complicated. A forum search didn’t help me very much and made it sound rather daunting, when perhaps it isn’t.
 
Malcyb said:
How do you do this (keeping it simple)? The Audi Workshop Manual link that @Techno posted is for refilling the system which presumably is a whole lot more complicated. A forum search didn’t help me very much and made it sound rather daunting, when perhaps it isn’t.
Click to expand...

This post from an earlier thread seems to provide pretty clear information, and is posted by another owner of a TDI 90:

Coolant replacement

I have to change my coolant radiator as the plastic tank at the end has cracked and leaks under pressure. Taking the front bumper off was a pita. How difficult is it to purge air from the coolant system when I go to refill it. Is there any tips for this procedure. Thanks, Brian
www.a2oc.net
 
steve_c said:
This post from an earlier thread seems to provide pretty clear information, and is posted by another owner of a TDI 90:

Coolant replacement

I have to change my coolant radiator as the plastic tank at the end has cracked and leaks under pressure. Taking the front bumper off was a pita. How difficult is it to purge air from the coolant system when I go to refill it. Is there any tips for this procedure. Thanks, Brian
www.a2oc.net
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Thanks, missed that somehow. However this has a range of methods from just running with the filler cap off to the whole drain and refill procedure at the other extreme. The former seems to have worked for some, so guess this is the one to try and see if it works?
 
Top up the expansion tank to the full cold level. Leave the cap off replace the bonnet and start the engine. Run the engine for a (considerable) period of time to get it fully warmed up. Ideally you want the fan to have kicked into high speed a couple of times. Turn off the engine, check coolant has not blown everywhere and dry up as needed. Recheck the coolant level and top up to max again with the correct diluted coolant and securely replace the cap and bonnet. Now take the car to do your essential shopping keeping one eye on the temp gauge. Should be bang on 90. When you get back let engine cool and recheck the level. All should now be good, no air in the system. I always monitor the level for a week or so just to make sure.
 
audifan said:
Top up the expansion tank to the full cold level. Leave the cap off replace the bonnet and start the engine. Run the engine for a (considerable) period of time to get it fully warmed up. Ideally you want the fan to have kicked into high speed a couple of times. Turn off the engine, check coolant has not blown everywhere and dry up as needed. Recheck the coolant level and top up to max again with the correct diluted coolant and securely replace the cap and bonnet. Now take the car to do your essential shopping keeping one eye on the temp gauge. Should be bang on 90. When you get back let engine cool and recheck the level. All should now be good, no air in the system. I always monitor the level for a week or so just to make sure.
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thanks, can’t get more concise than that. Just need to have a look to see if replacing the sensor is going to be easy enough for my limited skills... got to find it first!
 
Between the diagram of the parts and Toms picture you should be able to locate it quite quickly. Take a picture of your engine showing the tandem pump and the black plastic water pipe below it. From that you should be able to see the wiring plug fitted to the green sensor.
 
Malcyb said:
Slightly confused - are you saying I need to drain the cooling system after replacing the sensor, or just saying it needs bleeding to get air out like my central heating?
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Just saying that bleeding (like your central heating analogy) may help you out of your problem.
 
Malcyb said:
Does anyone think this is worth trying before swapping the sensor? Seems an easy thing to try
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I don’t think it will do anything
Engine will self bleed over time I.e. weeks or months and it will clear itself of trapped air whilst this is going on you will are the coolant level dropping
Assuming you are not seeing the coolant level dropping week on week then it safe to assume that there is no air int the system and therefore bleeding the system will have no effect on you temp gauge issue
Paul


Sent from my iPhone using Tapatalk
 
depronman said:
I don’t think it will do anything
Engine will self bleed over time I.e. weeks or months and it will clear itself of trapped air whilst this is going on you will are the coolant level dropping
Assuming you are not seeing the coolant level dropping week on week then it safe to assume that there is no air int the system and therefore bleeding the system will have no effect on you temp gauge issue
Paul


Sent from my iPhone using Tapatalk
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Well I’ve still not had the car that long but I haven’t seen the level change, so perhaps I won’t waste my time then.
 
Returned to work this morning after my 2 week ‘holiday’, the car didn’t quite get fully up to temperature as I hoped. My commute is a 12 mile mix of national speed limit country roads and a stretch of the A3 dual carriageway. Upon arrival in the car park I gave the bleed valve a turn and immediately some fluid appeared, as did the expansion valve when I carefully popped it open.
Dammit, the frustration continues!!!!
 
Does your car have all the shields fitted? Under tray, engine cover and foam underneath it? You could get a thermometer and stick that in the expansion tank after a run to manually check the water temperature, just do not have the engine running at the time and be careful removing the cap. How fast were you driving also makes a difference. Thermal efficiency of the engine was the reason the Webasto was originally fitted. I think all the air is out of the system now. Try driving it a bit harder to get more heat into the engine. A VCDS scan will show the temperature from both parts of the temp sensor and you will be able to tell is anything is wrong there. New thermostat may be incorrect rating or poorly made, replace for a good quality correctly rated one.
 
The drive in was done at my usual brisk pace, it has the under tray in place and the thermostat was a Circoli. I’m going to re-fit the old one to see if it makes any difference.
 
Make sure you get the correct thermostat for your engine. I have seen thermostats open at 80, 82, 83, 87, 88 and 109. If it opens too early the engine and gauge will be very lucky to get to 90. Conversely if it opens too late then possibility of head damage and boiling. Some thermostats have the opening temp stamped onto the body.
 
Without testing each one you buy, how does one tell?! The drive home this evening at a pleasant 22 degrees, predictably it warmed up nicely and stayed at an indicated 90 degrees all the way.
 
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