Coolant Temp sensor Issue ? -

Essexman

Essexman

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Its the age old coolant issue ive seen on so many old posts over the years- but had no success, so thought id ask here as to what to do/ check next (exept for scrap the car! lol)

Symptoms-
temp gauge on dash reads around just 60 / 70, possibly 80 in traffic, but this is after 20mins of driving! when it should way be at 90' by now,
After driving for say 45 mins, if i stop at a shop, get back in- it has a hot start issue (cranks over fine but does not want to fire) . well, just about after alot of persuation,


I checked for codes- shows temp sensor intermitent or not working

I have replaced temp sensor with a gsf car parts item, made no difference when installed, fault code remains, wiring looks ok
I shortly after replaced thermostat with a euro car parts item (only 3 months ago), this seemed to do the trick, the gauge on dash worked as is should and reached 90' no probs (so im guessing the temp sensor was ok & just the thermostat that needed replacing) i have been driving happy for 2 months ish, untill now the 'hot start' thing has become much more of an issue, i looked at the dash gauge & just like before- it only just creeps up to 70' after a long while. Surely this cant be the thermostat knackard allready! ?

I have the bolt down agu coil packs, the spark plugs look fine, i have seen on other forums & posts people say crank position sensor! ? but surely that wouldnt be it,

I am going to buy a new square temp sensor (and the other d shape one that sit near eachother in the agu), a new thermostat with o ring seal, new antifreeze & change that fresh 50/50 mix,

Only other thing i have seen is possibly its to do with the lambda sensor on exhaust (if i have one on the 98 agu)

Any other suggestions to make the dash gauge sit at 90' and the car start (fire) from hot/ warm ?

Would the maf be anything to do with it? even though the fault code read 'temp sensor' ?
 
Give the maff and the air inlet temperature sensor a good blast with brake or carb cleaner, did you clear the code after changing the sensors?
 
I only got a week out of a thermostat from euro car parts.
Get a gates or a genuine one.
 
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I had exact same symptoms, new Oem temp sensor had no effect so then I bought a new stat from audi as it was constantly open which sounds similar to what your problem is
 
ayfreetee said:
Give the maff and the air inlet temperature sensor a good blast with brake or carb cleaner, did you clear the code after changing the sensors?
Click to expand...

If it was these parts not working right surely you would know because it wouldnt run right and would show up on the error codes as a maf or inlet prob ?, no harm in me checking/ cleaning though i guess
 
Gonzokew said:
I had exact same symptoms, new Oem temp sensor had no effect so then I bought a new stat from audi as it was constantly open which sounds similar to what your problem is
Click to expand...

Has your same symptoms been fine ever since you fitted Audi stat ?
 
It was a Circoli one that lasted a week for me.
Buy cheep buy twice listen to Karl and get a good branded genuine one not a fake made in china.
 
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desertstorm said:
Never heard of Circoli and the Ebay item Hans Pries sounds German but they are made in China.
Buy cheap buy twice.
Look for Wahler, Febi, Meyle . Had a quick look on Fleabay I would go for this.
http://www.ebay.co.uk/itm/MEYLE-Qua...hash=item5d3b5d704c:m:mUUAIgwfploWsFkZvzUAK_g
Click to expand...

I have ordered the one you suggested,

I wonder if the fault code pointing toward a temp sensor will clear after the newly fitted thermostat
(never cleared when i put a new temp sensor in)
 
mine does the same after cts and thermostat change, subbed. guessing like others said we need genuine stat and sensor.
 
I used to have trouble starting the car sometimes when warm, if I'd nipped into a shop or petrol station, it'd always be a gamble as to whether the ig the car would start again or not. I was getting a code for the crank position sensor though.
Replaced that and it never happened again. I changed the stat about 5 months ago as it had always sat at around 70 since I bought it, it was just never that high up on my list of priorities
Then 2 months ago, the temp sensor went and the needle was all over the place, swapped that and it sits bang on 90 now when up to temp.

Thinking now I need to replace the coolant level sensor, as first thing in a morning when cold and I put the ignition on one turn without even starting the engine the coolant low light flashes on sometimes.
There's plenty of coolant in the reservoir so must be a sensor problem.
 
audi upgrades
I used motorquip stats on my old A3 and GTI without any issues, only about six quid.
 
So i recieved the Thermostat in the post yesterday, took the car to a friends yard to change the old/ new thermostat over (quite simple on a 98 agu compared to other years/ codes) :smile:,
(when i took the car it was cold at start of journey- started fine- i actualy stoped at a shop on the way like an idiot but wierdly on return to the car it started ok, just felt a bit weaker to fire) - carried on to mates yard,

Car cooled down for 2ish hours while we done other stuff elsewhere, then we got to fitting new stat,

the new one as suggested up there in the thread ^ is much more substantial than the euro cp item!, plugged it in with the new o ring seal, tightened up, put new anti freeze in, let it burp/ warm up with heater on etc,
I was now hoping the dash gauge would creep straight up to 90' but it never went past 72ish ' :-(

Turned car off, had a think / research with a cuppa tea

went back to car to drive home- then thats when it happened- the hot start prob! the worst its ever been, turning over fine but no fire up (tried a lil bit of this, a little bit of that, a little bit of throttle, a lot of throttle! lol, then 'just about' fired up, yesus, poor car, just ****** work! lol,
Stank of fuel,

got the vag com laptop out - no fault codes at all, (which is good that the temp sensor code has gone) but the hot start problem persists, as does the gauge on dash not hitting 90

which does it suggest something else not related to the electrics/ sensors, more of a mechanical thing? but how the temp gauge on dash & hot start prob are related i dont know.

Other forums suggest -

Fuel pump might be failing and there is a low pressure
Crank position sensor
Dirty fuel injectors
coolant temperature sensor
Clogged or dirty fuel filter
A bad fuel pressure regulator.

But i also saw this post - -

''I just wanted to let everyone know that my hot start problem has now been sorted. It turned out to be a weak starter motor which apparently is quite common on these engines according to the VAG master tech mechanic I used''

But surely its not my starter if it sounds like its turning over fine
 
Just to add- i unplugged the maf to see if that made any difference, no difference at all, so plugged it back in as norm
 
Just to Update- I had a hunch that the new coolant temp sensor i put in might of failed already (like the 1st stat !) because it was an ebay jobby etc (still says has 2yr warranty etc), anyway put another new one in & hey presto, job done, dash gauge shoots up to 90 after about a mile & stays there, which in turn hopefully sorts the hot weak start issue too, will see how it goes and report back, feels good knowing i put a new stat in too anyway, I've orderd a genuine temp sensor incase this one fails again !, hell i might order 3. :)
 
Is this the coolant temp sensor ur talking about ? As i replaced it also and had no changes still doesnt go to 90 until drivin for miles and even then can bounce back to 70
f5df1e0e7901cb4a3f6d444d4f79c3cc.jpg
 
Yes, except for mine is the square 4pin variant, have you changed the thermostat yet ? if not, definitely worth it as its a cheap part that could eliminate the prob, might be worth buying a new temp sensor too, test the old one you take out !, that will tell you if thats the prob or not, while your in the area might be worth checking the temp sensor 'plug' (on the wiring) with a multimeter, mine has survived so far, hope this helps
 
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