Water Temperature Fluctuations

[Regsmyth]

Bought an 03 1.9 TDI in February. So far so good, and passed MOT no probs in May.

I have the dreaded "sticky vanes" and limp mode issue to deal with at some point, but that doesn't seem too urgent at the moment.

 

I noticed shortly after buying it that the temp remained at around the 75-80 mark instead of 90, but today on a long motorway journey with lots of jams and congestion the gauge began to get a bit irregular, sometimes dropping to the bottom of the gauge, sometimes rising to 85 and sometimes going up and down quite quickly , but mostly still staying around 70.

 

I assume this is probably the thermostat not closing/opening properly, but I'm not sure if there is anything else that could cause this issue. Any thoughts would be welcome thanks. I changed the thermostat on my old Felicia successfully - is it a trickier job on the Octavia?

[pauldazzle]

Failing coolant temp sensor or stuck stat. Both are very common issues on VAG 1.9 tdi's. Advise you use genuine VAG parts for replacements. Buy cheap, buy twice.

[SuperbTWM]

My moneys on the thermostat. I've changed one on just about every VAG car I've owned. Because the temp gauge is 'frigged' to read 90 within a certain range a tired thermostat goes un-noticed unless you have something like VCDS to log temperatures.

[pauldazzle]

Agreed stuck stat by the description. I always check to see if a revised green CTS is fitted & change it out if isnt too, saves having to bleed& refill the system twice.

[Regsmyth]

Hmm, thanks for your thoughts. I'd decided earlier that it had to be the sensor failing, as the water temp surely couldn't fluctuate so quickly or drop to 50 (or below) in just a few seconds - how would a failing stat explain that?

 

What's a revised green CTS please?

 

So my plan was to replace the sensor first, (hopefully an easy job), and then see if that changes anything. Would that be the best idea? Thanks again.

[georged30]

Yes replace the sensor the thermostat would cause the indicator to fluctuate but slowly.

[bspman]

Since the others have already responded.. for your other issue:

 

 

I have the dreaded "sticky vanes" and limp mode issue to deal with at some point, but that doesn't seem too urgent at the moment.

 

FYI I mostly sorted mine out as follows:

 

1. run 2 full tanks of shell premium diesel (nitro+vpower or whatever it's called)

2. when your 2nd tank is nearly empty - chuck in 2 bottles of forte diesel turbo cleaner

3. Fill up with premium diesel

4. Drive in a "spirtited" fashion - hard accelleration, taking the revs up nice and high (with the odd redline) and generally keep them over 2k

 

I did number 4 both locally and (I'm pretty sure this is what fixed it) near red lining whilst going uphill on the m40 for a few seconds. Prior to this point I had to restart the car twice to get the boost back.

 

Have run it on the good stuff since and typically keep revs over 2k when I drive now (where possible).

 

Driving gently does cause the issue to re-occur, but again driving it hard sorts that out.

[SuperbTWM]

how would a failing stat explain that?

 

 

The OP used the word 'quickly' which is obviously down to interpretation.

[Regsmyth]

Thanks again.

The gauge would drop from 80 to 50 in just a couple of seconds, then back up, then more slowly etc etc. It was a long motorway journey with lots of congestion and stopping/crawling.

Same journey yesterday no traffic problems, temp stayed constant at around 80-85.

 

Freedom - re the sticky vanes - I noticed a lot of oil on the pipe to/from the intercooler, so I suspect the whole system will need quite a lot of attention. No doubt that'll be another thread...