About 5 weeks ago my wife told me while driving the orange engine management light illuminated & stayed on.The car ran ok though,idled slightly higher than usual on start up, but settled down to normal quickly.

 

I checked for fault codes & got one; 17704, which after googling I concluded I needed a new coolant temperature sensor.

I ordered a genuine one, cheapest I could find was here;

http://www.ebay.co.uk/itm/221307313459?ssPageName=STRK:MEWNX:IT

 

I fitted it in about 15 minutes, easy job.I drove for 15 miles after, all seemed fine, but as mentioned above, it had driven fine with the engine light on before I changed the CTS.

The light did not go out after those 15 miles,I was hoping it would have done but it didn't..... so I cleared the code myself, and this did make the light go out.

 

Now I'll get to the point of this thread;which is basically to give peace of mind to anyone using the search facility (for "17704") regarding the temperature gauge's readings.

 

I have read that the following is gospel; "the temperature gauge must be directly on 90 degrees (obviously after driving for a while to warm up) & not deviate from it's position, or there is a fault".(usually it's suggested to replace the thermostat).

 

The above (or similar) is what I am disputing.

 

Before I changed the CTS my gauge did stay on 90 & not move, but since replacing it, it  does sometimes reach 90 as a maximum...... but it also often stays lower.

It also does sometimes go as high as 90 (slap bang vertical, in the middle), then go lower.

In other words the above quoted "gospel" no longer applies, not to my car anyway.

 

The old CTS was black, the new one is green.

 

In my opinion, it is quite likely now giving a more accurate temperature reading on the dash gauge,than the old one, despite it's behaviour appearing to conflict with the "it must stay on 90 at all times or there's something wrong" school of thought.

 

For example, I have seen it reach 90 in slow moving traffic, then, when descending a hill shortly after, it falls to about 80, which if you think about it, makes sense, as the radiator would then be cooled.

 

Anyway,4 weeks on, & the car runs A1, the EML has not come on again, & I checked for fault codes yesterday, & there were none.

 

Hopefully this might be of interest to anyone worrying about their temperature gauge deviating from 90 (it has not exceeded 90 btw) after replacing their CTS.

 

On a side note, you can buy the CTS for about £3 more with the retaining clip included, I reused the old one, it was easy to remove the old one without it breaking.£3 saved, every little helps.

Edited 16 May, 201511 yr by Jonathan_1.8T

Sound like you have an air lock or the stat has stuck open. Once up to 90c it should stay there.

Plus one for sticky stat, I had exactly the same, would drop when off gas for long periods and go back to 90 when on gas. The ecu gets tricked into over cooling.

Sound like you have an air lock or the stat has stuck open. Once up to 90c it should stay there.

Cheers for the replies.

I don't mean to be funny in any way,I honestly don't, but says who?

I mean everyone seems to believe this because at some point someone said it, but if your car was at 90 in traffic, would you not (assuming the gauges job is to report accurately the temperature) expect it to drop if you went down a fast hill?

 

I don't suspect any air lock, I lost about 2 teaspoons of coolant when replacing the CTS, & the car runs perfectly since changing it.

What I am saying is, I can't see a reason to change the thermostat purely because the temperature gauge now works (imo) correctly.

 

If there was a problem either the car would run rough, be uneconomical  (recent 75 mph motorway trip averaged 39 mpg), or a fault would be present (no EML, no codes detected).

 

I just think people get conned sometimes into changing bits that don't need changing.

In fact I've read about other codes that I more-or-less ignored (because the car still ran fine & a solution was not certain/definite), which other have thrown literally £100's at, & still not cleared the code.

 

I respect folk do what they feel is correct of course, just saying I think you can worry over nothing sometimes & waste money.

I also appreciate at some point something may lead me to believe the stat needs changing, but it needs to be more than the temp gauge working as I think it should & others think it shouldn't (why do they think this?)

Edited 16 May, 201511 yr by Jonathan_1.8T

Every vag car I've owned and known when running right has never shifted from 90 when up to temp. I'm sure there are people here who can give a detailed explanation as to why, but suffice it to say if the gauge is dipping, it's not running right. Your mpg is slightly low as it goes, motorway run should return above 40. For a slightly sticky stat an mpg drop of that region is fully expected. People think these things based on fact and experience and solve the problems through knowledge sharing in forums like this. It's perhaps even more strange that when people are told things aren't right based on this experience they choose to ignore it. Don't mean that to sound harsh, but yes your gauge is working, but your thermostat isn't, well not at its optimum anyway and it's the kind of thing that won't cure itself.

Every vag car I've owned and known when running right has never shifted from 90 when up to temp. I'm sure there are people here who can give a detailed explanation as to why, but suffice it to say if the gauge is dipping, it's not running right. Your mpg is slightly low as it goes, motorway run should return above 40. For a slightly sticky stat an mpg drop of that region is fully expected. People think these things based on fact and experience and solve the problems through knowledge sharing in forums like this. It's perhaps even more strange that when people are told things aren't right based on this experience they choose to ignore it. Don't mean that to sound harsh, but yes your gauge is working, but your thermostat isn't, well not at its optimum anyway and it's the kind of thing that won't cure itself.

Thanks for the reply,

Points taken, I suppose the fact no other car I've owned does this fixed position thing & it *appears to be running A1* makes me reluctant to replace it......as you say if it's stuck or not right in any way it won't fix itself....I'm coming round to the idea I ought to change for peace of mind that it won't cause more apparent issues in winter if nothing else.

 

 

cheers.

Exactly, mpg is a sign it's not running right, may seem ok, smooth, starts fine, no misfires etc but like you say for peace of mind. Plus why burn more fuel than you have to its expensive enough.

P.s buy a genuine stat or you'll probably find yourself having a similar conversation in a few months time. I'm also pretty sure you will noticed an improvement in pull because the fuel - air mix will be bang on, plus you'll gain mpg.

Jon

My dirty diesel has a slightly stickijng stat and my mpg is down 4-5. Temp gauge should stay at 90 while ecu logs fluctuate a bit. Gauge drop means the coolent is being detected as much too "cold" thus over fuelling..

Cheers for the replies.

I don't mean to be funny in any way,I honestly don't, but says who?

I mean everyone seems to believe this because at some point someone said it, but if your car was at 90 in traffic, would you not (assuming the gauges job is to report accurately the temperature) expect it to drop if you went down a fast hill?

 

I don't suspect any air lock, I lost about 2 teaspoons of coolant when replacing the CTS, & the car runs perfectly since changing it.

What I am saying is, I can't see a reason to change the thermostat purely because the temperature gauge now works (imo) correctly.

 

If there was a problem either the car would run rough, be uneconomical  (recent 75 mph motorway trip averaged 39 mpg), or a fault would be present (no EML, no codes detected).

 

I just think people get conned sometimes into changing bits that don't need changing.

In fact I've read about other codes that I more-or-less ignored (because the car still ran fine & a solution was not certain/definite), which other have thrown literally £100's at, & still not cleared the code.

 

I respect folk do what they feel is correct of course, just saying I think you can worry over nothing sometimes & waste money.

I also appreciate at some point something may lead me to believe the stat needs changing, but it needs to be more than the temp gauge working as I think it should & others think it shouldn't (why do they think this?)

There is more than likely a problem somewhere on your system, as the dash panel insert already takes an average of inputs to it.

 

So, at an indicated 90 degrees on the gauge, the actual temp in the cooling system can be anywhere from 84 degrees to 94 degrees real time. It does this to actually stop rises and falls in gauge reading while driving and so define a stable "normal" gauge reading.

 

I to think you have a "sticky" stat. as the gauge should stay at 90 once fully warmed.

thanks Gents I've booked it in at The Phirm (Hartley Wintney, Hants).VAG specialist , didn't fancy the job myself, stat & coolant would have cost me about £50, they'll do it all inc, ( with a complete coolant change) for £151.That includes a new thermostat housing (apparently they're only £5 odd).All genuine Skoda parts.For the extra £101 cost over the parts,I'm happy to delegate it.

Are they charging 2 hours labour for that then? At least it will be done.

Are they charging 2 hours labour for that then? At least it will be done.

 

I don't know, possibly an hour & a half...I got a quote from Skoda, they quoted £163 just for labour (they said an hour & a half), no parts, not sure if that was with or without VAT.I ended that call pretty quickly.

I read up about the job & it looks like it could wind me up to the point where the £101 labour for someone else to do it is worth it.

Edited 19 May, 201511 yr by Jonathan_1.8T

It is tricky to get to if you've not simplified any pipework. 163 for labour haha that's funny. Yeah sometimes just pay out for less hassle.

all done, the only extra cost was £4-something for a new dipstick tube which broke during the work (as often happens apparently).Temp gauge now sits dead centre once the car's warmed up (10-15 mins), & it does seem to pull more smoothly.

 

Thanks for all input in this thread, much appreciated.

No problem glad it's sorted and you can feel the benefit. Yes those dipstick tubes are a pain, they get hot and brittle and quite often bits fall into the sump. Went to replace mine as a matter of course when simplifying some vac lines and it left the inner bit of the socket in the sump pipe when I took it out! Bloody things. Will be cleaning sump and replacing pick up pipe next oil change me thinks.