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Hi All,

Been a lurker on the forums for quite a few months now, and finally picked up my June’01 Avant last week. Needless to say, I’m pretty happy with it. It’s not my first quattro, but it is my first S version.

I’m not looking to do many mods, but one thing I’d like to do ASAP is something about an automatic afterun pump or whatever the adviseable equivalent is.

Now I’m no hot-shot mechanic (and don’t have the time or place anyway nowdays), however I have always heard it said that one should run the turbos at idle for at least a minute or two before switching off the ignition, especially after a 'lively' drive, so as to not cook the turbo/s (and the principal of burnt oil buildup makes sense to me).

I have a super-charged Mini, but the s4 is my first turbo motor, so I don’t have much experience on them, and I know very little, technically, about the s4 biturbo. My car has just over 40’000 miles, put on it by one owner whom I don’t know, so I’m assuming the worst, and that he never worried about letting the turbos cool properly. But I also assume that it is worthwhile to start looking after the turbos now, as I intend to keep the car a while. Reasonable assumption ?

If so, what is the easiest method ? A few months ago KayGee posted the following :

…The S4 is designed with an afterun pump but the original hardly ever runs as the water temp has to be very high. Simple mod, change the switch for a lower temp switch. Very cheap, very easy, very worth it even on a std car. …

Can anyone (KayGee?) break it down any simpler ? What is the temp switch which needs to be changed, can I change it myself, what parts, if any, do I need ? Where exactly is it under the bonnet ? Should I look at any alternatives or aftermarket offerings ? I would be grateful for any pointers on this, or on where to look for info on this subject, on the forum or elsewhere on the net.

I'd appreciate any help...

Thanks guys

Where's Dippy when you want him eh?

here ya go here's the how to guide.

http://forums.audiworld.com/s4/msgs/1629709.phtml

its something i had book marked cos i was going to have a go at this as well, seemed quite easy.
I decided against it in the end, I didnt want to bother get my finger dirty so instead i just run the engine as slow as possible for the last couple of minutes of any long or fast journeys.
Congrats on the purchase by the way.

Kwottro,

This mod is a pieace of pie! Really easy to do for less that £10. Phone vag-parts and order a Thermo Switch 021 919 369 and new O-seal 903 168 02.

Remove the screws holding the expansion tank as indicated in the audiworld post above, just move this out the way and you should be able to get to it fairly easy.

If you just losen the cap on the expansion tank this will stop you losing any water. I lost none changing mine.

Just pull the clip, dont lose it down the engine, work the plug lose and pull out, remove o-ring seal.

Smear some antifreeze around the new ring and seat it. then push the new sensor in and then secure with clip. Reconect the connector plug.

The new sensor has a lower tempreture value so it kicks in more often! Works great for me so far. And I have to trust this is doing the job!

I've bought the parts but haven't got round to fitting them yet. The following are the prices I was quoted a while back by www.vagparts.com are

021 919 369 – Thermo-switch £8.69+vat
N 903 168 02 – O-ring @ 32+vat

By the time they had replied I had bought the parts elsewhere and had paid much more.

Excellent. Thanks guys !

Must admit I didn't think to search on Audiworld. To be honest I don't go there much any more, as I get tired of the yank-speak, and I find the forum layout hard to read...

Anyway, I'll try to get the bits and do the job ASAP.

Forgot to mention that I'm in Switzerland...shouldn't make much difference, except here they'll probably try charging me even more for the parts than in the UK. If it seems way too much more, I'll just pick one up next time I'm over there - I wonder if the switch is a 'stock' part, or would a dealer need to order it in ?

One thing to point out is that there is a modified clip that Audi released for this sensor. The original one was plastic, the new one is metal - I advise you to get it if you are going to replace your sensor, as the new one can pop out under load (mine did). If you don't touch it, then you won't need it, as the original sensor is going nowhere with all those years of being subject to hot/cold temperature changes.

Did mine a couple of weeks ago pretty straight forward as mods go.As gavsteryoung said Keep sender attached to clip to aid in removal mine was tight as hell!!

Did mine last week. Got my parts through Lancaster Audi (as they deliver to my work place). Cost around £15 in total with VAT. Install was very easy... except getting the old sensor out was a pain. I tried using connector to pull it out but in the end needed to use grips.
Haven't noticed much of a difference, but I've only been driving to work and back really. I am pretty impatient, I usually only last about 30 seconds before turning ignition off. Considering a turbo timer, but that only helps with the cooling down, not when the car is started.
If you're staying stock (as I am currently, but not for long hopefully), then I wouldn't worry so much about it. Just take it easy for the first and last few minutes in the car.

This must the best mod you can do . I did mine when i did the kkko4 convertion ( as i dont want 2 have 2 do that again!!) Mind u i do get some funny look's as the fan keeps cutting in for several mins . G

Definetly best value for money/peace of mind mod around. Easy peasy, just remember to take out the old O ring. I paid about £11 inc VAT from local Audi dealer.

I keep meaning to getting around to doing this mod

A while ago I grabbed that article and saved it as a PDF for future reference (the images of the older articles tend to die on Audiworld). Grab it from here http://www.digitalphage.com/images/s4/L ... sensor.pdf (it's 306kB) if you want to keep a copy

Ok guys, So I'm presuming this will work for the rs4 aswell no?? same part numbers and everything??

Knew there was a temp activated cooling pump but that was about it....

Is this a revised part or just an unknown optional extra???

I'm pretty sure, but dont quote me on it but I think the replacement part is the standard temp thermo switch on the 225bhp TT. As I think they have a simlar afterun system..... could of just made that all up!

Lower temp thermal switch than the standard one. Comes from the VW Eurovan, VR6 12v engine. Basically two pin 93c temperature switch. I'm guessing it must be used in some other VR6 engined cars/vans since I got one in a day.

1.8T also has an afterun circuit as do some other N/A audis (2.8Q's have them), however they tend to use three of four pin thermal switches that perform other functions as well. These are more like our coolant sensors (the black or green one under the MAF accordian hose). Apparently the temp sensor is a common fault and causes bad idling and can cause misfires under load when faulty. Again cheap and easy to replace.