head gasket life?

[classicswede]

The amount of wrong information being preached as fact here is shocking.

Clearly Volvo got it all wrong and gave out wrong information in the green books and everyone who has been reusing the bolts just got lucky

[classicswede]

Yes it would be nice to sell new bolts to everyone everytime the head is refitted but the facts are the bolts can be reused

[Laird Scooby]

Originally Posted by classicswede

The amount of wrong information being preached as fact here is shocking.

Clearly Volvo got it all wrong and gave out wrong information in the green books and everyone who has been reusing the bolts just got lucky

You're absolutely right, it is shocking.

Those head bolts depicted in that image are NOT stretch bolts and can be re-used. Later stretch bolts have (if memory serves) a Torx drive.

[XC90Mk1]

Originally Posted by Laird Scooby

You're absolutely right, it is shocking.

Those head bolts depicted in that image are NOT stretch bolts and can be re-used. Later stretch bolts have (if memory serves) a Torx drive.

Stretch bolts are as you say are designed to stretch and not be reused.

The fitting of 12.9 bolts (1200MPa to yield in tension and 90% in shear) has no bearing on its ability to be reused (although if they are a different grade they may not function as intended.

Whatever is read you do not ever reuse stretch bolts. stretch bolts correctly torqued elastically deform and then can’t be used again.

What happens if you do use them again? That’s dependant on many things and you may well ‘get away with it’ but you will never meet a competent mechanic who offers to reuse stretch bolts.

[XC90Mk1]

Originally Posted by classicswede

The amount of wrong information being preached as fact here is shocking.

Clearly Volvo got it all wrong and gave out wrong information in the green books and everyone who has been reusing the bolts just got lucky

That would appear to indicate that if the bolt is stretched then replace. And if not stretched then replace after 5 torques anyway.

[Laird Scooby]

Originally Posted by XC90Mk1

That would appear to indicate that if the bolt is stretched then replace. And if not stretched then replace after 5 torques anyway.

Absolutely spot on! The waisted section is what allows those non-stretch bolts to stretch in service (rather than shear) and once five torques have been applied, they should be renewed regardless.
If they are stretched, they should be replaced as a full set, not just the one or two that are showing signs of elongation.

[griston64]

Originally Posted by classicswede

The amount of wrong information being preached as fact here is shocking.

Clearly Volvo got it all wrong and gave out wrong information in the green books and everyone who has been reusing the bolts just got lucky

Is that image exaggerated ? I don't recall the bolts I removed from my 98 940 having such a pronounced waist section

[360beast]

Stretch bolts removed from a 1995 940 B230FK, I have only ever seen stretch bolts like these in 940 engines.


IMG-20220120-WA0019 by Luke Ryland - Flickr2BBcode LITE


IMG-20220120-WA0016 by Luke Ryland - Flickr2BBcode LITE

[griston64]

Originally Posted by 360beast

Stretch bolts removed from a 1995 940 B230FK, I have only ever seen stretch bolts like these in 940 engines.


IMG-20220120-WA0019 by Luke Ryland - Flickr2BBcode LITE


IMG-20220120-WA0016 by Luke Ryland - Flickr2BBcode LITE

That's exactly the same as the ones I removed from mine last week. It's not as pronounced as the drawn image but it does have a waist. It also states if in doubt do not reuse, so in my book it's not worth bothering with the old ones. If you are rebuilding an engine ( especially with higher power ) it would be a false economy to me !

[deeman940]

i have come round to thinking that the only solution is to do the job again by someone i trust and would be rude not to drop some forged rods and/ or pistons while the head is off.......