Thermostat questions

[Numero9]

Got all the symptoms of a stuck open thermostat so plan to change it this coming weekend however watching a few videos I've confused myself any need some help clarifying a few things

1) is it right that in later GTi (mines 08) there is more in line stat and only the main one to replace?
2) seems to be 2 options remove intake or remove alternative, is there a preferred method from those who have done it themselves?
3) watching one video there was a comment about also changing the o-ring on another pipe but I can't remember which video said it or where the o-ring was, does anybody have a diagram for where and possibly a part number?

I know it'll be a pit.of a.job but I have a full day set aside to oil change, coolant flush and this and quite looking forward to it...

[mjmallia]

It all depends on the gearbox you have to my knowledge.

Manuals have one near the alternator.  This is for the Turbo and prone to failing like mine did, as it stuck open and never go to temperature...........fine now.

The second/additional one is for people who have DSG, and that sits above the box and works for the box

[Numero9]

Sorry should have said its a manual 08. From what I read the DSG and 3 and the manual has 2 but also ready the inline was deleted so a later GTi should only have 1

[pudding]

Have a look in the engine bay to determine it for yourself.  As stated, the thermostat count varies with model year and gearbox type.  My manual 07 has 1 thermostat.

Removing the alternator is the best method.  It's dead easy once that is out of the way.

[LC5F]

The whole "3 thermostat" thing was just on early cars - as Pudding said - check how many inline ones you have -if any. not cheap, over £40 each a few years ago. As an example my 2006 DSG has a single inline.

If you are changing the main thermostat, consider doing the coolant temperature sensor at the same time, as it is mounted within the thermostat housing - sods-law guarantees it to fail within 6 months if you don't change it!

Alternator off is the best way forward, but tight if you have large hands, making the whole job awkward - I have not seen inlet manifold off as a suggested route - it would be a $ite ton more work and has the potential to create more problems.

[Numero9]

New thermostat and sensor ordered. Are there any other o-rings or bits that I should replace along the way?

[OllieVRS]

New thermostat and sensor ordered. Are there any other o-rings or bits that I should replace along the way?

I had a coolant leak from the o-ring on the main thermostat (marked 5 on this diagram), the part number for it N90365302, might be worth replacing while you're in there

[FatWelshBoy]

The specialist I use changes thermostats by removing the inlet manifold as he says it is the easiest and quickest way, he has done 100's so take what he considers easy with a pinch of salt.

[Numero9]

I'm going to go down the alternator removal route with this. Seen a few videos on that way and have had prior experience on my other car on removing the alternator and getting it back it.

@OllieVRS - where did you get that parts diagram from?

[OllieVRS]

I'm going to go down the alternator removal route with this. Seen a few videos on that way and have had prior experience on my other car on removing the alternator and getting it back it.

@OllieVRS - where did you get that parts diagram from?

I think off of Google images, I pulled this image off one of my older threads when I was investigating my coolant leak. Also to clarify since there are multiple rings marked 5, it's the one with the red arrow.

I've found a similar diagram which is even better detailed: https://workshop-manuals.com/skoda/octavia-mk2/drive_unit/2.0/110;_147_kw_fsi_engine/engine_cooling/parts_of_cooling_system_summaries_of_components_engine_identification_character_bwa/parts_of_cooling_system_engine_side/

The O-Ring I'm talking about is marked 9 on this one, directly below the 26.

[Numero9]

Collect all the parts tomorrow & fit over the weekend plus an oil change.

Any other tips or guidance would be much appreciated & thank you all so far!

[mjmallia]

Alternator out and a couple of hose clamps to stop/slow the flow of coolant out the system.

[Numero9]

going to drain the coolant, not sure when it was last done and for the sake of few £ rather drain and change it. Definitely going with alternator out method

[Octoparrot]

I'd also remove the fans if possible. it's tight in there.

[breeze]

I did this myself a little while back. Alternator route, leaving the fans in place.

Horrible job to do on your back and I actually managed to make a mess of the o-ring which meant that it was compressed in the wrong position. That had the impact of backing out the bolts. I ended up giving it to a specialist who said that the water pump was also leaking. £750 for refitting the thermostat, doing a cambelt and water pump.