Who has replaced a coolant temperature sensor..?

[MijIsTired]

… on a 1.2l tsi petrol, 2011?

 

Now I’ve finally found it (thanks to the legends that are @Breezy_Peteand @sepulchrave) and seen how buried under hoses it is, wondering what the minimum number of things it’s possible to detach to make it sensibly accessible. 
 

Started with the chunky air cleaner hose but while I could shift the clips easily enough, the hoses weren’t budging so had to give up for the night. 
 

Wondered if it would be better remove the duct that comes off the top of the radiator, but the rigid plastic snibs that click it in to place are equally reluctant to give up. 
 

So hoping for pearls of wisdom about which one to concentrate on, before I get the better tools out and lose more time to things that may not buy me that much extra space. 
 

Thanks in advance. When I get properly in there I’ll do a few photos in case it helps those trying to do the same. 

[J.R.]

If it is held in by the plastic C clip like I think it is then you can replace it working by feel alone, you dont need to see what you are doing, granted until you have done it once it will not be so apparent what to do.

 

Removing the wiring plug is usually the hardest, once that is done the sensor should be relatively easy.

[sepulchrave]

You should remove whatever you need to gain adequate access, probably both the items you mention.

 

I think you might benefit from using a mirror and a torch because it will still be hidden under the thermostat housing unless you remove the housing itself.

 

You'll need to drain the coolant into a clean washing up bowl so you can pour it back in again.

 

As @J.R.says there is a plastic C clip holding the sensor in place but you don't have to remove the plug itself until the sensor is swinging freely from the lead which will make it much easier to see how to remove the plug and will also stop you dropping it somewhere inaccessible.

[Breezy_Pete]

Held in by a single torx screw I believe, but you may well need to remove the metal bracket that screws through the housing next to it (as seen in the close-up photo of the position in the ebay listing linked previously in other thread).

 

 

 

How sure are you that it's faulty?  My advice would be to disconnect and inspect the connector before anything else, looking for any sign of corrosion on the contacts or damage to the wiring near the cable entry.  Do you know the knack of removing these connectors?

 

[MijIsTired]

On 17/10/2023 at 15:17, J.R. said:

If it is held in by the plastic C clip like I think it is then you can replace it working by feel alone, you dont need to see what you are doing, granted until you have done it once it will not be so apparent what to do.

 

Removing the wiring plug is usually the hardest, once that is done the sensor should be relatively easy.

Thanks, at the moment I can’t get at it sufficiently to do anything other than just about touch it.  

Edited 18 October, 2023 by MijIsTired

[MijIsTired]

On 17/10/2023 at 16:42, sepulchrave said:

You should remove whatever you need to gain adequate access, probably both the items you mention.

 

I think you might benefit from using a mirror and a torch because it will still be hidden under the thermostat housing unless you remove the housing itself.

 

You'll need to drain the coolant into a clean washing up bowl so you can pour it back in again.

 

As @J.R.says there is a plastic C clip holding the sensor in place but you don't have to remove the plug itself until the sensor is swinging freely from the lead which will make it much easier to see how to remove the plug and will also stop you dropping it somewhere inaccessible.

Thank you, I’ve seen some helpful posts about how to deal with it once you can get at it, but always useful to mine prior knowledge about best approaches.

 

Mirror & torch - check. 
 

You underestimate my ability to drop anything, anywhere. Dexterity is not my strong point.

[MijIsTired]

On 17/10/2023 at 17:50, Breezy_Pete said:

Held in by a single torx screw I believe, but you may well need to remove the metal bracket that screws through the housing next to it (as seen in the close-up photo of the position in the ebay listing linked previously in other thread).

 

 

 

How sure are you that it's faulty?  My advice would be to disconnect and inspect the connector before anything else, looking for any sign of corrosion on the contacts or damage to the wiring near the cable entry.  Do you know the knack of removing these connectors?

 

Always delighted to hear about knacks for doing things. Consensus is to disconnect first, but other tips very gratefully received. 
 

OBDll had wild temperature readings from a stone cold engine, and others experiencing the same seem to find replacement = solved. 
 

Only error code is intermittent EVAP which I’m also replacing. 

[sepulchrave]

You won't get a fault code from a failing ECT sensor until the output actually falls outside a plausible range.

[MijIsTired]

3 hours ago, sepulchrave said:

You won't get a fault code from a failing ECT sensor until the output actually falls outside a plausible range.

 

Not sure whether to praise your prophecy or blame you for invoking it, but ta-da! Last night the ECU light came on to have a party with the red flashing temp, and OBD now shows 'low circuit' fault P011700. Intermittent Evap hasn't recurred though. 

 

Coolant level still fine. Red temp dash light coming and going, with no pattern/correlation to anything I can discern re driving conditions, start up vs mid-drive, load the engine's under, or even whether parking uphill, downhill or flat. 

So current plan is still to remove whatever's in the way of seeing it properly, check as much of the wiring to and around it, and unless there's a really easy to see other cause (eg dodgy wire), replace it. 

[Breezy_Pete]

There's a fair amount of choice of video guides for connector unplugging if you've never done one before. 

The executive summary is "push connector body towards sensor before trying to release latch".

Many latches are broken by those who do not realise this simple technique is required.

vw connector removal - YouTube

[MijIsTired]

Great, thank you.

 

About to go in 🤞

[MijIsTired]

Got the little sod out.

 

 

Had to fish around for a while, hooking out bits of O ring with an adapted paper clip. Glad the second one is green or I’m not sure I’d have spotted the remnants.

 

Used a combo or torches, mirror (thanks @sepulchrave) and phone camera for the ability to zoom in. 
 

Ended up taking out both air hoses and the air filter housing (which was surprisingly easily to remove. Never had need before), and the battery. Disconnected one of the radiator coolant hoses and it was still a bugger to get to.

 

@Breezy_Peteinvaluable info again, both about location and getting the connectors off. Watched videos, had a practice on more accessible ones and voila! That stage could easily have been where I got defeated without this intel.

 

Massive thanks again to Briskoda’s finest. 

Edited 21 October, 2023 by MijIsTired

[J.R.]

That looks like it put up a fight, good on you!

[MijIsTired]

On 21/10/2023 at 20:50, J.R. said:

That looks like it put up a fight, good on you!

Thank you 😁 It’s satisfying isn’t it.

 

Also (touching lots of wood) happy that have had no reoccurrence of non-starting since, though can’t find a reasonable explanation for that as it seemed to be lack of sufficient fuel to get a first spark up.