cam tensioner earth

[Bigvolvo]

Having scrutinused some detailed 912 engine drawings it appears my auto tensioner should have a wee earth strap attached...well it ain't. I imagine it's purpose is to relieve the belt of static. So is my Excel going to start emiting wierd light effects without it?

[fueltheburn]

The whole of the block should be earthed anyway - the tensioner is bolted to the block.
Any static buildup will be transferred through the securing bolt to the block.

Imagine a strap getting caught in the tensioner if it became loose or breaks, that wouldn't be good.

[pompey ice]

Hi ,The tensioner bearing pivots on two nylon bushes and the other end sits on a plastic tensioner spring cover

so in effect its completely insulated ,to be on the safe side I have replaced mine ,maybe it was fitted to stop radio interference

One of our members did mention the name of the effect that can be caused by the cam belt ,cant remember what it was but it

did sound Dutch [ Van der Graaff ] found it in my scribbles

Cheers Ian

[Jason.goad]

So without that wire, you'll become a fan off prog rock.

[AndyC]

To clarify for anybody reading this later, both Fueltheburn and Pompoey Ice are correct for the respective cars, plastic bushes on the pivots for the semi-automatic tensioners on earlier cars, earthed via the bolt for later cars with manual tensioner.

[fueltheburn]

Whoops - Blinded by what I last looked at just remember seeing the tensioner on Ethel's engine forgot the early ones have an auto tensioner.

[Bigvolvo]

Van der Graf sounds appropriate- remember the demo at school? (if you went to one!) a chrome ball which built up very high voltage but low current-made your hair stand on end.
My Excel has the 'auto tensioner'. Not that there's anything auto about it- you manually adjust the tension, just in a different way to the later one.
There was no wire at all on mine and no nib nearby to attach one two. I also dont remember anything nylon.
The engine will be coming out next spring so I will look further into it then......
So has anyone modded a later tensioner to fit the earlier cars?

[AndyC]

The earth on the semi-auto tensioner is from the bolt at the axis of the bearing to the mounting bolt. The nylon pivots are a pair of (thin) top-hat bushes. It's referred to as semi-auto in that it adjusts the tension slightly if the belt becomes loose, unlike the manual ones where the tensioner is completely fixed and so the belt can become much more loose.

To fit a manual system, you need to use one of the later air conditioning or alternator strap brackets, this provides the position and guide to drill the hole that is needed. The hole isn't present on the earlier cars but the casting is fine for it, just don't go deeper than the correct distance. Then you need to tap the hole, obtain the boss that is pressed into the bearing and it's ready to fit.