Coolant temp sensor

[rickparmar]

Scanned my S3 and this came up,

Its easy to replace and will get part this week, but what i want to know what does it mean exactly,

i know it effects

It can cause the ecu to cut back on boost,
It can cause soft limp mode and poor running.
It can make you feel you have a boost leak and
It can provide false reading that could cause lean or rich running.
It could cause strange dash temperature readings.

but what exaclty does it do, and how does it work

Thanks

 

[Stewart]

Take it on face value, its a 'coolant temp sensor'.

It's a sensor that measures coolant temperature

But seriously, the whole engine management is optimised (well, generically optimised as factory settings can be) for 'normal' running conditions and temperatures. Normal meaning working temperature. If the ECU is being told that the temperature is anything other than normal then it is programmed to assume that either the engine is on cold warmup or overheating/running hot (due to hard driving) so ******* various settings to protect against engine damage.

 

[jbkudos]

You say its an easy job?? Ive had a look in the haynes manual and it looks pretty tricky!! Mine has obviuosly gone aswell any chace of taking a few photos when you do yours?

 

[rickparmar]

Have a look here

same as a S3, not sure about A3 tho

http://www.wak-tt.com/tempsensor/tempsensor.htm

 

[AndyMac]

took about 15 minutes to change mine on the A4, just unplug the wiring, remove the circlip that locks it in place and lift it out. Make sure you take the top off the expansion tank first to release any pressure in the system, otherwise you get a facefull of antifreeze (like I did)

 

[madvw]

...and how does it work

The coolant sensor is a thermistor. Basically a variable resistor which is affected by temperature. The ecu takes this resistance reading as the car's coolant temperature.

 

[rickparmar]

What a difference this made, completly feels like a new car

Wish i checked my car with a vagcom when i first got it

 

[jbkudos]

Was it easy rick?

 

[rickparmar]

Was it easy rick?

very easy, but loads and loads of coolant came out

 

[jbkudos]

whereabouts in the engine bay is when you look at it with bonnet up?

 

[rickparmar]

whereabouts in the engine bay is when you look at it with bonnet up?

have you sorted it yet mate ?

 

[jbkudos]

no gonna try and get my brother to have a look at hes a bit morew technically minded than me

 

[jbkudos]

where did you get the part from?

 

[rickparmar]

Got the part from audi, £22 plus vat

you have to take the plastic engine conver off

then on the right hand side you will see a wire going into the temp sensor, need to pull a clip out then change the sensor

but make sure you open the coolant bottle up,

 

[D-Tech Performance]

easiest way to describe it is its the green thing in a hose

 

[rickparmar]

easiest way to describe it is its the green thing in a hose

lol but the old one is black

 

[D-Tech Performance]

lol this is true sometimes green sometimes black majority we come accross have been green lol

 

[nik patel]

Rick do you have to keep the coolant cap off throughout changing the sensor? or just take it off before you start and then put it back on before starting?

 

[rickparmar]

I took it off, but still lost alot of coolant, but then i put cap back on and the coolant stoped squirting out if that makes sense

so what i was, open it, and close it striaght away then remove temp sensor (hopefully it should stop the coolant suirting out)

 

[AndyMac]

Yes you have to take the cap off to release any pressure, then put it back on so that air can't get back into the system. This prevents the whole of the expansion tank emptying itself via the coolant sensor.

 

[nik patel]

cheers, looking at many posts on here it says changing the coolant temp sensor will solve my occasional starting probs? or do i have to change another sensor?

 

[rickparmar]

nik have you got a vag com ?

 

[AndyMac]

It's a common failure and can cause all sorts of wierd issues, depending on the fault. Mine caused my car to stall when the engine was cold, I couldn't believe the difference just by changing this £20 part. It can also cause just rough idle, high fuel consumption etc really depends if it's telling ECU the engine is hot when it's cold or telling it it's cold when its not.

 

[rickparmar]

It's a common failure and can cause all sorts of wierd issues, depending on the fault. Mine caused my car to stall when the engine was cold, I couldn't believe the difference just by changing this £20 part. It can also cause just rough idle, high fuel consumption etc really depends if it's telling ECU the engine is hot when it's cold or telling it it's cold when its not.

your 100% spot on there mate, my car feels like its been mapped just by changing this part

 

[jojo]

your 100% spot on there mate, my car feels like its been mapped just by changing this part

You've obviously never driven a mapped S3 Rik.

 

[rickparmar]

You've obviously never driven a mapped S3 Rik.

lol your coments always make me laugh

well it will be mapped soon, then we shall meet next year at GTI International - Deal

 

[jojo]

lol your coments always make me laugh

well it will be mapped soon, then we shall meet next year at GTI International - Deal

I will be up for it mate, if I still have the S3.

Time for some

 

[rickparmar]

I will be up for it mate, if I still have the S3.

Time for some

Come on you know you want to keep it, You still got a load of mods to do to the car

What would you like next ?

 

[jojo]

Come on you know you want to keep it, You still got a load of mods to do to the car

That's the thing Rik, I've not got round to fitting everything because 1. I havn't had the time, and 2. Maybe I'm actually bored of the car, despite the fact it ticks a lot of the boxes.

What would you like next ?

Something more track focussed?, something with 300BHP minimum!


I think I have done something like 2500 miles in the last 10 months in my S3, which makes it an official weekend car, so might aswell buy something a bit more raw I can have some fun in.

 

[rickparmar]

you should get a BMW M3, and leave the S3 as your main weekend car,

Whats the millege now on the car ?

 

[nik patel]

Rick i dont have VAG.COM. How longs does it take to change roughy? and how much is the part?

 

[rickparmar]

Rick i dont have VAG.COM. How longs does it take to change roughy? and how much is the part?

took me bout 5 mins, lol

no tools needed and part is £22 plus vat

 

[nik patel]

Dont you have to take the engine cover off and the other little one in front of it to gain access?

 

[rickparmar]

engine cover is held on by 2 screws

 

[rickparmar]

have a look at this link,

where about do you live?

http://www.wak-tt.com/tempsensor/tempsensor.htm

 

[nik patel]

what link?

i live in Harrow

 

[nik patel]

cheers guys for your help, since changing it, the problem has gone!

 

[potter]

Can failed coolant sensor cause engine manegment light to come on.