940 L reg alternator tensioner MISSING!

[allank]

Hi,

My first post here so thanks for having me

I've recently gone back to my youth and picked up a mid-rough 940, MOT somehow! Sills need done and general rust.

Diagnosing the engine squeal, I realised the alternator belt needs tensioned. It turns out the tensioner bolt is MISSING! It's actually sheared off in the threaded tensioner stud. So, stud/lock-nut and bolt required.

I see you can buy the entire assembly from the US for quite a lot - I obviously just need the threaded lock stud and a long-ish bolt. Any ideas please?

The two photos are: 1. My broken/missing parts, 2. A working example.

https://photos.app.goo.gl/5TUQ7698FYDuzwaq6

Cheers, Allan

[B10B]

Yes it is common for the treaded 10mm bolt to shear off. The cause is nearly always due to forgetting to tighten the 13mm nut after the tension has been achieved with said bolt.
Easy reliable fix; get another person to pull the alternator up to tension the belt somewhere near 1/4" deflection, then tighten the 13mm nut as it is this nut that keeps the alternator locked in position.
Worked on my old Wentworth for 3 years and countless miles before I sold it.

[allank]

Thanks, I note the Haynes actually says to do this or to "lever the alternator away from the engine to achieve the desired tension." Well that'll work!

Allan

[B10B]

Yes as long as the stud and 13mm lock nut are still serviceable it will be fine.
The 10mm threaded bolt is purely to tension the belt, not keep the alternator in place.

[Forrest]

If it bothers you, you can obtain a complete replacement

https://www.skandix.de/en/spare-part...nator/1018610/

or just the long 10mm bolt

https://www.skandix.de/en/spare-part...anism/1018622/

but it looks as though yours might have sheared off in the threaded hole in the head of the 13mm bolt. This will either need carefully drilling out and re-tapping or it will be easier to replace the whole thing.

[Ian21401]

Originally Posted by allank

Thanks, I note the Haynes actually says to do this or to "lever the alternator away from the engine to achieve the desired tension." Well that'll work!

Allan

My Volvo is the first car that I have owned which has this method of adjusting the alternator and/or PAS pump belt tension. On all my previous cars it was a case of loosening the clamp bolt and the bolt onto the engine bracket and levering the alternator until the belt tension was correct than tightening the aforementioned bolts.
I was pleasantly surprised by the Volvo method which makes it easier to adjust the position of the alternator by using the adjuster. It must be remembered though that the clamp bolt and bracket bolt need to be loosened before attempting any adjustment using the adjuster, then tighten them when required adjustment is achieved. Some oil onto the adjuster threads to prevent corrosion is beneficial. There is a school of thought which suggests that once the alternator is clamped into position the adjuster should be backed off slightly to remove any tension. I can see the logic in that but I have never actually done it. I have heard of people trying to use the adjuster to move the alternator without first loosening the aforementioned bolts. That, of course, will break the tensioner.

[lynns hubby]

As people have said on here, its not really necessary but its nice if its there and works as it makes adjusting the belts easier.
I believe that people are getting confused with the bolt head size and not the thread. Its a 6mm (M6) bolt of which the head is 10mm. Its a common way to describe bolts in the motor industry, even haines manuals refer to head (spanner) sizes and not thread sizes.

That said, if you really want to get the long bolt, find a fastener place near you, there is bound to be a nut and bolt supplier close to you or just use Google to source a bolt. I would suggest its high tensile and not one of those cheap and nasty "Gutter Bolt" type things you can pick up in B&Q

[griston64]

£3.85 for four

https://www.ebay.co.uk/itm/181806653...r=480752610661

[lynns hubby]

They look good. Tensile as well

[TonyS9]

The long 10mm bolt is available in any B&Q.

It looks like it will be difficult to remove the broken stud from the remaining threaded bolt head. I would try a rust dip solution clean it off, or ask a workshop to remove it.