knock sensor plug pigtail
 

The knock sensor plug pigtail looks to be disintegrating.
I have only done a general visual inspection of everything I can see in the engine room while I have removed all the plastic covers.
But from what I understand looking through old threads where MJ shows photos and comments, it is something better left untouched?
I looked at one of your photos MJ, with the manifold removed. No way I can get to that.

By the way, I do not have two green knock sensors, but one green and one orange.

*I hope I use the correct words for the parts. I could find knock sensor cables in online shops, but not the plug pigtail*

Araldite? ;)

Interesting suggestion, would that work? On the other hand it would look pretty awful, I fear.
But it might be the only option. As I cannot risk removing the manifold and drop some dirt into the engine

I had both of my knock sensors replaced a while ago. One of the plugs had disintegrated just like yours so I suspect it's a common issue. From memory, the sensors weren't too expensive and came complete with new leads and plugs.

Yes, it is a common problem. Somehow Bosch managed to make the connectors from a plastic which doesn't survive the heat of an engine bay http://www.corradov8.com/pics/banghead.gif

You can't just replace the connector unfortunately. Its a screened cable which is very difficult to work with. The connector colour denotes the cable length by the way.

Tbh if taking the manifold off is not an option I would be inclined to go with Andrew's suggestion of an adhesive product to hold the connector together. Yes, it has a high risk of looking fairly awful, but thats really all you can do with the green one. The brown one is on the outside of the V though, behind the power steering pump, so that can be changed without too much difficulty.

Normal "domestic" Araldite is nominally only rated up to 65C, but would probably be OK. I'd probably risk it on my own car.

Better to find a 2-part epoxy adhesive rated for a higher temperature as the engine bay will normally be over 110C; there are loads available, Araldite themselves have a huge range.

Or look at UV-cured adhesives, again a wide choice. I've used Bondic which I think is OK up to 150C; it's also clear and easy to build up so can be tidy.

Thank you for all your comments. I see my options might not be set in stone, especially since Mark had his replaced without any issues.
I won't try to remove the manifold myself, as that would end in disaster, I am sure :)

I wasn't brave/skilled enough to do the job myself, nor did I have the tools or time to do it, so I gave the job to my mechanic.

Apart from the broken connector and an intermittent knock sensor fault, one of the reasons I decided to get the job done was because I had some oil leakage and fumes coming from under the inlet manifold (plus I wanted to fit a spare new manifold that I'd purchased some years ago). The leak was caused by a failed gasket on the cover that sits in the 'valley' of the Vee (whatever it's called?). If your valley cover gasket has never been changed, it's likely it'll be very oily and gunky under there like mine was, so it's probably worthwhile lifting the manifold off just to replace the gasket and remove all the gunk.

Mark,
How did you determine a knock sensor fault?
Did it show on diagnostics, or did you have pinging?

I ask, as I get pinging from the S8 under moderate load in 3rd gear acceleration (labouring engine).

I also have cracking in at least one of the knock sensor plugs, and I've been wondering if one of them might be faulty?

I only use 98RON and often add octane booster, especially for trips.

I didn't notice any pinging but that could just be because my exhaust is so damn loud! Plus it was just an intermittent fault, which flagged a fault code, but only very occasionally. Unfortunately I don't appear to have kept a record of the fault code but, IIRC, it quite unambiguously pointed to the knock sensors.