Hi, so after generally resealing the engine (while doing DMF change and turbo/intake cleaning I did basically all gaskets/seals other than head gasket) and achieving up to 1,5l/100km less consumption the engine now didn't get up to temp, that is, it gets there veeery slowly, and is always a bit off the 90°C, never really in the middle.

 

Figured, hey, it's over 30°C outside, its definitely the thermostat (although it was changed a few years back), changed that, it was "OK" for a few days, now again... Today I've driven a tour in 30°C for 25km's and after more than 10km's it got up to temp, but then again it started dropping. Again from cold after 8 km still not up to middle mark, just a bit off.

 

Before the engine "overhaul" it did get to temp a bit quicker and the gauge needle was in the middle, but generally I expect it that when it's so hot outside it would heat up in no-time, but never really heats up, what it's gonna be like in the winter??

 

The only thing I can distinguish now than before when it heated up more quickly that I use the AC more (and that the engine works much much better and has a new thermostat)...

 

Could it be the temp sensor or something else?

 

Mind you, I'm coming from a Fabia vRS with PD engine, in this hot weather it gets up to temp in no time, but also has a non linear gauge, as when coolant is ~65°C it shows the dial in the middle as warmed up, maybe the old Octy isn't linear but exact?

 

Please help...

 

P.S. it's one of the last old 1.9 TDI AGR engines 90hp...

 

These do suffer with coolant temp sensor failure. If going to replace it, only fit genuine parts as the cheap ones fail quickly. 

@Juka - Agreed; this sounds a lot like CTS failure, and that you should only buy a genuine VAG replacement.

If I may piggyback onto this thread my '03 1.9tdi (taxi motor- ALH) started with some odd low reading for coolant temperature during the freeze last November. Sometimes it reads a steady centre dial (90C?) and others it floats about quarter way up.

 

I've checked water pump return (good), coolant levels and heater performance and all are ok, so I'm assuming I also have a sender problem ...

 

Whereabouts is the sender? Can I test it with hot water? Do I need to bleed or flush the cooling system if I remove/replace it?

 

Best source for a replacement? 

 

Thanks in advance for any and all help.

 

Regards, Mike

@StickyMicky - I'd agree that this sounds like a CTS sender issue. If you own a VCDS you can use that to log CTS output against time.

 

Which part of "genuine VAG replacement" is unclear to you?

13 minutes ago, KenONeill said:

Which part of "genuine VAG replacement" is unclear to you?

 

No need to growl, Ken. I was wanting to know the best source (ie recommended dealer, website) for such parts.

 

Don't own VCDS unfortunately:(

Edited 22 June, 20187 yr by StickyMicky
update

2 minutes ago, StickyMicky said:

 

No need to growl, Ken. I was wanting to know the best source (ie recommended dealer, website) for such parts.

Web prices vary, and you can use a search engine and make your own decision. Also note that I did agree your probable diagnosis first, and that people ignoring the "buy genuine CTS" advice is a common problem on VAG enthusiast sites.

28 minutes ago, KenONeill said:

Web prices vary, and you can use a search engine and make your own decision. Also note that I did agree your probable diagnosis first, and that people ignoring the "buy genuine CTS" advice is a common problem on VAG enthusiast sites.

 

Cheers, Ken.

 

I'm currently looking at stuff via my mobile, so not the easiest with ageing eyes, but I found a post about CTS replacement for a VRS where the OP suggested what appeared to be a part from a VAG supplier. I'll re-find the post when I get back to base and put up the details.

I've personally witnessed a faulty CTS on an 2003 1.9 TDI ALH, but the symptoms were erratic working of temp gauge needle; is my problem a second mode of failure, where it works, but incorrectly measures the temperature?

 

Come to think of it, I also have the issue that the engine cranks for a really long time until firing up, this mostly happens when it's warm outside and the engine is "cold". If it's cold outside, or the engine is warm, it cranks and fires up almost instantly. AFAIK this could also be a failed CTS?

 

@StickyMicky you asked how hard is it to change the CTS, I've also changed it on the said ALH, it's a few minutes job if you know what you are doing, I'm sure youtube is full of DIYs.

 

My CTS only gave an indicated 89deg if i was pointing downhill stopped in traffic for atleast 5mins. Other than that it was. 70deg all day long regardless of ambient weather. 

It never hurt the engine, still got 55mpg at motorway pelt in an ALH.

 

Update on the topic, I've visited my mechanic and he measured both the actual temp of coolant, and ECU readings. Both actual and ECU are the same, 90-95°C, but the needle still shows 80~85°C. Seems it could be a gauge cluster problem?

11 minutes ago, Juka said:

Update on the topic, I've visited my mechanic and he measured both the actual temp of coolant, and ECU readings. Both actual and ECU are the same, 90-95°C, but the needle still shows 80~85°C. Seems it could be a gauge cluster problem?

 

There are two separate/independent NTC thermistors in your (4-pin) CTS. One gives info to the ECU, the other to the gauge cluster. Just because the ECU one is giving good readings doesn't mean the other is.

Well, glad to hear that, then it's definitely the CTS.

 

Now I'm wondering, I sometimes get the dreaded long cranking, almost doesn't matter if the engine is cold, hot, or "medium", it's just random, this is supposedly cured by changing out the CTS? Maybe it doesn't read linearly throughout the temp range, or just intermittently doesn't read as it should and it cranks for long... Will change it out soon.

I suspect that is a different problem; let us know if it goes away with a new CTS though, please.

And buy a genuine CTS or you'll be posting in 3 months time that the aftermarket one isn't working or that the temperature problem never went away after changing the CTS. VAG engines don't like non oem sensors.

Just a quick recap, I've changed the CTS two months back (didn't have time to fiddle with it so I just left the car at the first garage and let them change it, thus non-OEM :( ).

 

The temp now reads correct and gets to the middle, even warming up in these colder days its no problem.

 

I still have the intermittent "long" cranks, although much rarer than before. What I did notice though, mornings are now quite cold and then the car fires up instantly, and I literally mean instantly, there is just a single crank and it runs. If I could only get this during warmer days... Anyone know anything about this?

On 30/09/2018 at 11:43, Juka said:

Just a quick recap, I've changed the CTS two months back (didn't have time to fiddle with it so I just left the car at the first garage and let them change it, thus non-OEM 😞 ).

 

The temp now reads correct and gets to the middle, even warming up in these colder days its no problem.

 

I still have the intermittent "long" cranks, although much rarer than before. What I did notice though, mornings are now quite cold and then the car fires up instantly, and I literally mean instantly, there is just a single crank and it runs. If I could only get this during warmer days... Anyone know anything about this?

 

To answer myself, I got the car remapped and it was sorted within the map, the crank is now instant on cold and hot. It's got to do with less fuel injected on warm start due to emissions reasons, and the ECU linearly correlates crank revs with less fuel injected. With age the starter cranks even slower thus even less fuel is injected and that's why sometimes it cranked really long.

 

Must admit that this starting is even more satisfying than upping the engine from 90 to 120hp (mind you, the dyno showed 95 healthy hp prior to remap, after 19 years and 330kkm!)

 

P.S. the "third party" CTS that was installed last summer still shows good temp readings.