Technical Timing belt tensioner nut

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Technical Timing belt tensioner nut

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My 16V car had a special two part 13mm nut to hold the tensioner. It looked like an ordinary nut apart from the copper colour. Inside the nut was a steel coil of wire like a recoil. Presumably nobody is going to recoil a nut??

The steel core was made from very strong steel spring wire. The outer part of the nut came off leaving the inner part holding the tensioner.


Do I need a special nut on the tensioner?
 
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The local garage had no idea what i was talking about with the strange nut. They gave me a nut with a few markings out of their box of stuff and said it would be OK
 

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Hi Judderbar, you probably had a one time use nut , crush nut, there is coil that crushes inside when tightened to the correct torque setting and stops it coming loose, when you undo the nut the coil inside all mangled, so you can’t use it again. They’re quite expensive to buy from fiat.
 
Looks like appropriate thread for my question:

How do you torque this nut while holding the tensioner at correct setting? The funny little key used to hold the tensioner is nowhere strong enough to hold it while you torque the bolt to required 25 Nm. Seger pliers aren't up to the job either. Should I just loctite this bugger?

c9a1a57744979916ca88b5aea741.jpg

It is an unusual nut but the one on my engine is intact. Is it really a one time use?
 
Looks like appropriate thread for my question:

How do you torque this nut while holding the tensioner at correct setting? The funny little key used to hold the tensioner is nowhere strong enough to hold it while you torque the bolt to required 25 Nm. Seger pliers aren't up to the job either. Should I just loctite this bugger?

View attachment 203575

It is an unusual nut but the one on my engine is intact. Is it really a one time use?

I reused my nut many times before it finally fell apart the last time I undid it.

When you torque the bolt can you previously arrange the tensioner so that if the tensioner rotates it will give you the correct tension? I have done this job many times with circlip pliers and only just decided to get the small tool to avoid all the hassle.
 
When you torque the bolt can you previously arrange the tensioner so that if the tensioner rotates it will give you the correct tension?

Finally I did it this way, it gives a few more Nm but not the required 25. Apparently some FIAT trainers said you can put a washer under this nut but I'm reluctant because I don't want to leave the nut flush with the end of the bolt.
 
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Finally I did it this way, it gives a few more Nm but not the required 25. Apparently some FIAT trainers said you can put a washer under this nut but I'm reluctant because I don't want to leave the nut flush with the end of the bolt.

A bit late now but having the spring tension slightly tighter will not make much difference to the tension on the belt. What is vital is having the correct torque on this critical nut if you have a 16V engine and you cannot perfectly know what your torque is using a torque wrench. Thinking about it now makes me want to go to Fiat to get that fancy nut. 25nm is not much torque on a nut on the side of a vibrating engine. :(:eek::yuck::cry:
 
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