My A3 1.8T Coolant Sensor

ricje

ricje

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Hello you lot. Just purchased a 99 1.8T had it a month no problems great fun to drive, proper step up from my mk3 gti.

One prob, seen some of you lot mention it: Temp never gets to 90 degrees in less sitting in traffic (or turn it off for a bit and turn it on).

VAG COM gives a G62 Temp Sensor Intermitent reading, only error returned by vag com (apart from 2nd key problem but not important)

Thought I d give changing the temp sensor a go to start before I move to the stat to see if I could sort this. Got the green temp sender, took over engine cover(s) pulled it out and......

Its blue and it has a four pin SQUARE plug on it.

Have a bought a A3 with dodgy bodge parts on it :blink: ? Am I pulling out the right sensor :blink: ??

Any help would be VERY appreciated :sorry:
 
hiya,
just take the sensor back to the dealer and they will swop it for the blue one, not sure what the difference is but i think dealers just assume you need the green one as most have them fitted instead. My '99 1.8t also has a blue one? don't think it's just pre-face lift that have blue ones?
 
cheers mate, thought i might have bought some dodgy make-shift A3 as I see all the A4 owners talking about the square (instead of the round) fitting sensors. Put my mind to rest appreciate it :lmfao:


thea3.jpg
 
NO NO NO!! Don't return it. That's the updated version. Phone them and ask if you're not sure. I have the green one, which replaced the blue one. As long as the sensor is the same shape and number of pins, it good!! It's just the replacement part for one that was a poor design.

Also the same for window clips and possibly much more! But that sensor is the right one!

Andy.
 
nop it's a different part, the green one is oval shaped and replaces a blue/black one, some cars including A3's and A4's have a square socket and require a different sensor, i'm not 100% sure if they have actually revised the part or not.

078 919 501 B is the square one i removed from my car but i'm not sure of the part number of it replacement.

059 919 501 A is the green oval one
 
....its also a common failure on the 1.8T. Good news is you may actaully find it a bit quicker once done, the faulty sensors sometimes pull the boost back a bit as it thinks the engine is still cold, so wont gove full boost. Noticebale if its remapped for sure!
 
hi guys i to hve this problem, i need to change my temp semsor, can u tell me where it is loated so i can remove it, cheers
 
Anyone know where this is located?

A pic would be most appreciated.

I've had the problem since I bought my car 6 months ago but didnt fix it as the fans still kicked in so didnt see it as a problem but after reading that it can affect the power, I would like to get mines fixed asap too.

Cheers fi the wee man wi a big chair.
 
thought Id update on this one.

Got new sensor (blue/square). Didnt work :mad: . Got another one. Gets up to 90 degrees now but only while Im in traffic. As soon as I give it some beans it goes right back down to around 70 degrees.

As far as I am aware the 1.8T is supposed to be good at keeping the car level at 90 when up to temp.

So whats next to fix this? Is it an electrical fault do I need to get a sparky on it? Or is it more serious.... :notme:
 
VAG-COM Version: Release 311.2-N
Control Module Part Number: 06A 906 018 AQ
Component and/or Version: 1.8L R4/5VT MOTR HS D03
Software Coding: 04000
Work Shop Code: WSC 06313
1 Fault Found:
16502 - Engine Coolant Temp. Sensor (G62): Signal too High
P0118 - 35-10 - - - Intermittent

Was this the code you got?
i have this code and it kinda made me think about the comment on cutting the boost back. cos when my car was dynoed it had a dip at torque peak which could be this sensor playing up! hope it is cos its well weird! n annoying.
 
If you're temp rarely gets to 90, then your thermostat is broken. Mine was broken, which I proved after I had removed it, by boiling it in water.

It's quite difficult to get in and change it, but the reward is better running temperature, getting to that temp much quicker and better MPG as a result!!
 
I changed mines the other day as I said I would.

My car used the square plug which I got from Audi at a cost of 26 pounds.

It now works perfectly. A lil more boost and from the way I was driving it last night (Hard and Fast) I will be getting maybe 3 more miles to a gallon. Was only out for 2 hours last night and used 10 pounds of fuel Eeeeek. I had to. It felt like a new car.


Remember that if when you push the car and the temp drops its probably cause its pulling in more air and cooling quicker. You might running the engine quicker but once you slow down, you might find that the temp goes back up to 90 degrees as there is less air circulating to cool the engine down.

I could be wrong but in theory it sounds right.
 
I can't say I've ever experienced that. Even on a 130 hoon!

Always BANG on 90.
 
Mine does this too :(

It's done it for a while but it seems 'worse' recently.

Previously, i'd put it down to it being Winter and it taking longer to reach temperature but now i'm noticing it fluctuate. In fact it never seems to reach 90. It'll sit just below 90 or fall to just above 70.

I just scanned it with VAG-COM and i have no fault codes.

I already have the 'green' coolant temp sensor so i guess i'm gonna need to change the thermostat.

Anyone got a guide to changing the thermostat? Also a part number would be usefull as my 'copy' of ETKA has packed up. It's a 1998 A3 1.8T Sport (AGU).

Cheers.
 
Sounds exactly the same as mine Tallpaul. Hope changing the stat will make it work again properly. Any luck with instructions on how to do this?
 
It's not a long job to replace it thankfully. You have to drain the coolant, and takethe earth lead off the altenator.

MAKE SURE you tie this up out of the way of anything, you or the engine. I didn't do this and blew a fuse on top of the battery, which I later found out was 110Amps!! Suffice to say you DO NOT want that to go through you!

You will need a 3/8 universal joint to get tthe right angle for the bolts that hold the housing in place. When you pop the thermostat out is will be pressurised on the other side, cos it will still have some coolant on the other side. Leave the cap off the expansion tank to make popping it out easier.

I tested my original stat in some water before replacing it, just to be sure, but you may want to just get it in there, so up to you.

Make sure you get the sealing O ring sitting right as you don't want to do this more than once.

Part numbers, diagrams I here you say?!?

Thermostat.jpg

The stat is no. 6 audi/GSF should supply the O ring with it.

Hope this helps.
Andy
 
ah crap, is it really a coolant out job?

That's a PITA, the coolant in there is only a year old :(

I was kinda hoping the thermostat could be whipped in and out and all i'd need to do was top up what was lost.

Thermostat was easier to change on my mk3 Escort (first car, don't ask)!

GSF do the part for about £9.
 
Yeah you really should drain it, but you can reuse the coolant, so you don't have to replace that. Alternatively, you could try plugging the pipe to the radiator, but you will still have all the coolant the other side of the stat (about 50%) rather than just a trickle, and it WILL come gushing out. With the altenator in such close proximity to what would be the direction of flow this might not be a good idea.

It's really not a long job to drain it. You may find that you end up worse off money wise for not draining.
 
Im going to have to go for it this temp things annoying me and Im sure my MPG is suffering. Just hope I dont electricute myself!!!!:rockwoot:

If the stat was bust would would normally come up in VAG-com ??
 
ricje said:
Im going to have to go for it this temp things annoying me and Im sure my MPG is suffering. Just hope I dont electricute myself!!!!:rockwoot:

If the stat was bust would would normally come up in VAG-com ??
Click to expand...

There's are degree's of bust. Presumably it's still giving a healthy signal, albeit intermittantly wrong. The ECU probably only throws a fault if it stops receiving a signal or the thermostat kicks out a silly voltage.
 
my temp reading has been playing up as well. im guessing mine is the temp sensor, i say guess, as it randomly drops to 60deg while driving. i know the cars at temp as it will sit there fr ages but if i take another glance at it, its at 60 again. i saw it fall today, looked like a second hand on a clock the way it was moving. when it was in for a service i mentioned this but they only vagcom'ed it and cos it didnt give any faults they did nothing about it.
jus the prob these days, they rely too much on these sensors and computers to tell them whats wrong!
prob have to give this ago my self
 
Just to get something straight...

Where does the Temp Gauge on the dash take it's reading from?
 
as far as Im aware, from the ECU which gets it from the coolant sensor.

Found a specialist that will do the stat for £28 quid in hexham so Im going for that (lazy route :icon_thumright: )
 
So....

If the coolant temp sensor is measuring the actual coolant temp, and that is what is being displayed on the dash.... how can it be the thermostat that's broken?

If my coolant is slow getting to temp and falls when i'm driving, what has this got to do with the thermostat? In fact, what is the thermostat doing? Is it just a switch that turns the fans on and off?

I doubt in this weather i'm ever needing the fans to cut in as i never sit in traffic and its ****** cold outside.

Therefore my coolant temp is really fluctuating and not simply the gauge is displaying a false result? This sounds more like it either is due to the outside air temps or that i have blockage in the coolant system or something?

I think i'm gonna idle the car 'til the fans cut in and monitor the temps on the gauge and on VAG-COM. If the fans cut in at just above *90°C and that is the temp on both the gauge and VAG-COM then where is there an actual fault??
 
the thermostat simply blocks the flow of water going to the radiator until the engine is warmed up. If its blocked open this is why its taking so long to get up to temp. Also explains the reason why it drops quickly as the thermostat is not closing therefore constantly flowing coolant into radiator. I think :icon_thumright:
 
ricje said:
the thermostat simply blocks the flow of water going to the radiator until the engine is warmed up. If its blocked open this is why its taking so long to get up to temp. Also explains the reason why it drops quickly as the thermostat is not closing therefore constantly flowing coolant into radiator. I think :icon_thumright:
Click to expand...

Gotcha :)

That makes sense.
 
Yes, that's exactly it. The stat blocks coolant from flowing round the radiator until it is at a temp to open the stat to start cooling.

You can check if both stats are working by boiling them from cold in a saucepan of water. Do the good one first, which should open just before 90, and then do the one after you take it out of the car and you will 99% find that it opens way sooner than the new one.
 
Well my new thermostat and sealing o-ring are sat in front of me... Total of £14.40p delivered next day from GSF.

Whats the best way to drain the coolant?

I can get to the thermostat from above but presmably the radiator bottom hose is gonna have to come off so i'll need to be on axle stands to get a bucket under there? What's the volume of coolant?
 
Changed the thermostat this morning...

What a PITA. If you're trying this i defo recommend you get a bottle of G12+ as well, fortunately i had one anyway.

Good news is, problem solved. Temp gauge sits bang on 90degC :thumbsup:
 
Tallpaul said:
Changed the thermostat this morning...

What a PITA. If you're trying this i defo recommend you get a bottle of G12+ as well, fortunately i had one anyway.

Good news is, problem solved. Temp gauge sits bang on 90degC :thumbsup:
Click to expand...

Result dude! It is a ****** of a job! I did mine from the top. Did you use a UJ to get to the bolts? Taking them out was no prob, it was getting them back in that was an a**e hole!

How much coolant escaped?
 
LaSarthe&Back said:
Result dude! It is a ****** of a job! I did mine from the top. Did you use a UJ to get to the bolts? Taking them out was no prob, it was getting them back in that was an a**e hole!

How much coolant escaped?
Click to expand...

Yeah, getting the bolts off proved to be the easier of the jobs ;)

I removed the earth strap and loom from the alternator, i also removed the bracket for the lower engine cover for a bit more room.

In draining the coolant i only lost a couple of hundred millilitres from behind the old thermostat when i removed it.

The big losses came when i fitted the new one, refillled the system and ran the car up to temperature. Lots ****** out where i hadn't fully tightened the bottom bolt :jester:

After stripping it down again, ensuring the thermostat and seal was properly seated, properly tightening the bolts (!) and refilling it, everything was good. I probably wasted about 1 litre of coolent.

My universal flexi and 10ml socket wouldn't fit in the gap behind the alternator so i had to use a smaller flexi that only flexed in one direction.

All good now though :)

Just got to change the oil and get through my MOT tomorrow and all will be well (hopefully).
 
hey guys i have an audi a3 quattro sport 180bhp and my temp sensor is black? having problems with idle when pulling up at traffic lights? any ideas what colour sensor it should be and why the idle will be playing up? cheers.
 
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