Hi Guys (and girls)

My temp guage has for the past 6 months been sitting around the 70 mark (during normal driving), I changed the sensor with one bought from ebay about 5 months ago, which never really cured the problem, but as I thought cheap ebay item, maybe it doesn't work.....

So on the weekend, got one from Skoda, changed it and still having the same problem.

I have had the 17704 code come up, which points to the sensor or thermostat

Other than taking the thermostat out which i won't do as I'm as mechanically minded as a goat, is there any other way of troubleshooting if it's deffo the problem?

Coolant levels all ok

Oh, and i did manage to get it up to 90 degrees, but I let it warm for ages on the drive, and then took the rev's up to 2000 for 30 secs or so, and it did creep up there....

So, if the thermostat was knackered, would it do that??

Any advice appreciated

Thanks

Steve

Sounds exactly like the thermostat. Mine behaved this way until I changed it, runs at 90 now fine.

Are the fans running most/all the time (both of them, not just the one cos that means the air con is on)?

Are the fans running most/all the time (both of them, not just the one cos that means the air con is on)?

Hi Ken

I just went outside and started her up, nope, the 2 fans by the rad were both off, but both came on when I turned the climatronic (heating, not cooling) on

Of course, at the moment she is cold......

Ok, quick update......

Drove home from work, temp stayed on 70 until I got stuck in traffic, then went up to 90, as soon as I moved off, it dropped back to 70

Left it running on the drive, got back up to 90, so left it to see if the fan cut in, it did after being at 90 for a little while, ran for a minute or so, then cut back out......

Steve

For the fans to cut in, there has to be hot coolant in the radiator (there is a thermo switch in the radiator for the fans). For coolant to get into the radiator the thermostat has to be opening properly, otherwise the coolant just pumps around the block, header tank and heater matrix.

From memory on the 1.8T the thermostat is supposed to start opening at 87 degrees and be fully open by 103

I've had to do similar checks with mine this week as have been getting an intermittent 17704 error for ages and changed the coolant temp sensor at the weekend, hoping that will have done the trick as taking the thermostat out sounds like a real ballache.

Edited 25 January, 201016 yr by chicken_eyebrow

For the fans to cut in, there has to be hot coolant in the radiator (there is a thermo switch in the radiator for the fans). For coolant to get into the radiator the thermostat has to be opening properly, otherwise the coolant just pumps around the block, header tank and heater matrix.

From memory on the 1.8T the thermostat is supposed to start opening at 87 degrees and be fully open by 103

I've had to do similar checks with mine this week as have been getting an intermittent 17704 error for ages and changed the coolant temp sensor at the weekend, hoping that will have done the trick as taking the thermostat out sounds like a real ballache.

But I think it might be stuck open, like I said it very rarely gets up to temp whilst driving, only when left running but not moving.......

Other than take it out (garage job cos I'm not that mechanical) is there any other way to check?

Everything else seems to work as normal, fan kicks in when it's supposed to etc.........

I thought the thermostat was supposed to be failsafe, ie when it fails it opens rather than stays closed? Otherwise you'd be driving along seeing no temp reading yet the motor could be cooking? I seem to remember reading a thread on here about it a couple of months back when mine was playing up.

I can only imagine that, when the stat starts to fail, it opens at lower temps leading to over-cooling especially at motorway speeds. It's only when stationary or at town speeds where enough heat builds up under the bonnet to get it anywhere near 90.

Either way, mine was reading between 70-90deg and all I replaced was the stat. Problem sorted.

The symptom you describe of 70 while moving and 90 when in traffic is definately the thermostat stuck OPEN (so you dont have to worry about cooking your engine should it ever fail as in the above posts). I have recently changed my Engine temp sensor and thermostat and had the same symptoms, it was the thermostat that fixed it. Not the easiest of jobs but with the right bits and pieces it is possible without removing/loosening the alternator and definately do not remove the Throttle Body (unless you plan on doing a TB clean while your at it) If you want to know more about the how let me know.

The symptom you describe of 70 while moving and 90 when in traffic is definately the thermostat stuck OPEN (so you dont have to worry about cooking your engine should it ever fail as in the above posts). I have recently changed my Engine temp sensor and thermostat and had the same symptoms, it was the thermostat that fixed it. Not the easiest of jobs but with the right bits and pieces it is possible without removing/loosening the alternator and definately do not remove the Throttle Body (unless you plan on doing a TB clean while your at it) If you want to know more about the how let me know.

Karl can you PM me some details as the code has come back on mine and the symptoms are as above it generally sits at around 69-79 degrees while driving but goes up to 90 when sitting in traffic after giving it a good blast (the coolant temp gauge sits on 90 but I'm getting these figures from my Liquid Gauge), so looks like I'm going to have to change the thermostat. As it doesn't seem to be damaging the car I will probably try and do it in the spring when I can get out on the driveway

Are the fans running most/all the time (both of them, not just the one cos that means the air con is on)?

I have also found that when it's cold inside the car the air con was on as well, spooky.

for anyone that wants to try the thermostat for them selves this is the best guide I found http://forums.audiworld.com/showthread.php?p=16925102 However is easier to use a mini ratchet with an allen bit for the bottom bolt as it is really awkward to get a bulky 1/2" drive socket bendy bit and the 10mm socket into that tiny gap. Might be easier if your socket set is 1/4" drive

I thought the thermostat was supposed to be failsafe, ie when it fails it opens rather than stays closed?

Not true at all. Almost all modern car thermostats are the waxtat type. The thermostat is a valve which is pushed open against a spring by wax contained in it's bulb which expands when it reaches a certain temperature. It's very possible for it to fail in the closed position, and two common reasons why it can fail to open are:

1. The thermostat has been fitted the wrong way round, which means the wax bulb is facing the cool side.

2. The engine has previously overheated for some reason, and thermostat has got so hot it's wax has become very thin and become lost. In this condition the thermostat will not work, and the engine will overheat. Often when this happens traces of wax can be seen floating in the expansion bottle.....

Thanks for all the advice guys, booked in for tomorrow, will let you know if it sorts it.

Will also let you know what they charge......

Cheers

Steve

Hi Guys

Just got the car back, only driven it 2 miles, but temp settled at 90 and didnt budge (must have still been warm from test drive)

The garage I use the mechanic has a leon with the same engine, so loves working on my car......

Anyways, thought I'd let you know the charge.......

On the invoice it has replace Thermostat and Antifreeze, £30 labour, £15.87 parts

Total with vat of £53.90

Cheers

Steve

Ive been having the exact same problem as you Steve ,put new temp sensor in, keep clearing the 17704 code and it comes back, and im getting 26- 30 mpg .

Thats seems a very fair price your guy charged you , so where abouts are you in the country as i would not mind using your mechanic .

That's a good price indeed Steve, glad to hear you got it sorted.

I don't want to be smug but.... I said it was the stat! :rofl:

LOL, I told you so.........smug away........

My garage is in a little welsh village called wattsville, they service our works cars and vans, and always look after us, but then we do spend a fair bit with them over the year

Moores Motors is the name

Dont mind recommending them to anyone, they always do a good job, and are very reasonable price wise

Cheers

Steve

that price is too good. I would check what antifreeze he has used as G12 would cost that alone.

Ok, quick update......

Drove home from work, temp stayed on 70 until I got stuck in traffic, then went up to 90, as soon as I moved off, it dropped back to 70

Left it running on the drive, got back up to 90, so left it to see if the fan cut in, it did after being at 90 for a little while, ran for a minute or so, then cut back out......

Steve

how long should it take for the temp to hit 90? it takes me just under 15 mins to get to work and mine barely touches 90, most of the time it's running at 70.

Is it time to replace? i've replaced most fecking things on the car, wouldn't want the thermostat to feel left out

Edited 28 January, 201016 yr by skillo

3-4 mins tops once you are moving. If it stays at 70 when driving and only gets close to 90 when stationary then yes it is time to change the thermostat HTH

I've got the stat for mine in fact I've had it weeks lol

What tools would I need to change it ???

Was there a guide iirc.

3-4 mins tops once you are moving. If it stays at 70 when driving and only gets close to 90 when stationary then yes it is time to change the thermostat HTH

Thought so, just ordered myself one.

Does that explain why my heaters take for ever to warm up, or are they just poo anyway?

I had exactly the same thing, was taking ages for it to get up to 90c, then it'd back down again.

Local garage changed it for £15-20 on my service.

When I did it I only needed to put about 300ml of G12 coolant in to top it back to where it was. There's a guide on one of the audi forums or have a search.

I just removed engine cover, the cable tray at the front of the intake manifold and unplugged the block connector to the alternator. That was enough for me to get some grips on the hose clip and remove it (loses a small amount of coolant) and then get access to the stat housing. With the stat housing removed the stat normally stays in place, so you need to have the new one ready with the o-ring in place, then do a quick-ish switch with the old one. Don't worry too much about the coolant gushing out, it looks like there's more than there actually is. Make sure you have a litre bottle of G12 on hand to top up afterwards and be careful to fit the stat the right way round.