V70: snapping bolt and a raft of pain..

[100K+]

Today I bought 6 of each of the attached M5 bolts to conduct destructive testing.
ALL bolts failed at 20MN ( the smallest number my torque wrench can be set to) The round head bolts snapped off like licorice, without sound, the hex heads snapped with a "crack". Additionally, I tried a couple of each type with my 1/4" drive ratchet, and was surprised how little effort was required to snap either type. Both types turned under the same level of force, but the screw head turned only a third turn before it came apart, the hex head would turn almost a full turn before sheering with a "crack". These hex heads also could be turned one way and then the opposite way without visible damage.
The place I got them said they were "8.6" and good quality.
My thoughts now are I think I have turned my filter bolts to the same levels of force as I have with these test bolts. Only the "slipping" of the bits used within the bolts has saved me from snapping them. ( the 27 torx bit was a good tight fit after I'd tapped it home) If I use a 6mm fluted bolt extractor, it may well grip very well, but with no give, if I exceed what force I have already applied, a snapped bolt will result. I don't think I can do any more.

Think its time to call this a day..

Thanks again to all who contributed..

Cheers
Bob

[green van man]

Originally Posted by 100K+

Today I bought 6 of each of the attached M5 bolts to conduct destructive testing.
ALL bolts failed at 20MN ( the smallest number my torque wrench can be set to) The round head bolts snapped off like licorice, without sound, the hex heads snapped with a "crack". Additionally, I tried a couple of each type with my 1/4" drive ratchet, and was surprised how little effort was required to snap either type. Both types turned under the same level of force, but the screw head turned only a third turn before it came apart, the hex head would turn almost a full turn before sheering with a "crack". These hex heads also could be turned one way and then the opposite way without visible damage.
The place I got them said they were "8.6" and good quality.
My thoughts now are I think I have turned my filter bolts to the same levels of force as I have with these test bolts. Only the "slipping" of the bits used within the bolts has saved me from snapping them. ( the 27 torx bit was a good tight fit after I'd tapped it home) If I use a 6mm fluted bolt extractor, it may well grip very well, but with no give, if I exceed what force I have already applied, a snapped bolt will result. I don't think I can do any more.

Think its time to call this a day..

Thanks again to all who contributed..

Cheers
Bob

Do you know that volvo used 8.8 standard bolts?

I have high tensile M5 socket head that are 10.9 rated.

Surprisingly cheap in comparison to bigger sizes for 10.9 rated bolts. I bought them to fit a new door module to my xc70 when I found the gap between box and hole was too small for a normal sized pop riveter. I drilled the holes in the door card out to 7mm and used M5 rivets to fix the module. Bolts well greased of course to enable the next one to be fitted easily.

Paul.

[100K+]

Originally Posted by green van man

Do you know that volvo used 8.8 standard bolts?

I have high tensile M5 socket head that are 10.9 rated.

Surprisingly cheap in comparison to bigger sizes for 10.9 rated bolts. I bought them to fit a new door module to my xc70 when I found the gap between box and hole was too small for a normal sized pop riveter. I drilled the holes in the door card out to 7mm and used M5 rivets to fix the module. Bolts well greased of course to enable the next one to be fitted easily.

Paul.

Hi Paul This is engineering theory - something I know NOTHING about. Do you know how much stronger 8.8 rating is over 8.6? The lad at the engineering factors where I got my bolts said the allen bits I used which rounded out the the filter bolts, he thought were 12 point something which is why they gouged out the bolt innards - that and the fact they were corroded to hell and back..

Cheers
Bob

[Bob Meadows]

Maybe an idea?
Clean as much rust off the bolt & areas as you can:~ make a well out of plasticine or similar around each fastener securely adhered etc.

Fill the well with your favorite releasing fluid and then leave it as long as you can-the concentration of fluid for longer may just help and creep further.
Good Luck
Bob.

[green van man]

Originally Posted by 100K+

Hi Paul This is engineering theory - something I know NOTHING about. Do you know how much stronger 8.8 rating is over 8.6? The lad at the engineering factors where I got my bolts said the allen bits I used which rounded out the the filter bolts, he thought were 12 point something which is why they gouged out the bolt innards - that and the fact they were corroded to hell and back..

Cheers
Bob

Ohhh err. I know the numbers reffered to tensile strength which is longitudeital strength , what you are talking about is torque or sheer strength ie resistance to turning force. Which will depend upon the material the bolts are made of.

Your test with the torque wrench with clamped bolts recorded a figure where the bolt failed, however I have found this to vary dependent on not 9nly the material but the shape of the head. Dome headed fail far quicker than square shouldered socket headed bolts of the same material, as I find the hex socket rounds out before the bolt snaps. I avoid dome headed bolts where ever possible for this reason.

I mainly have to deal with stainless steel grub screws, the heads of which are often below the surface of the aluminium housing. Invariably the socket fails before the bolt. Stainless steel bolts also have a treacle tendency to spalding. I know engineers whom use a galvanised nut with a stainless steel bolt for this reason. Again try undoing a spalled stainless nut and bolt. Better off cutting it off and start again. Plenty of grease is the only remedy I have found.

Not a lot of help to you I know. By now my head would of gone and it would be off the car and fix it once and for all, I appreciate you are trying to avoid this. But my patience would of been exhausted and I could not live with knowing I had failed. Have cost myself thousands over the years, but it was that or loose sleep with it niggling at me.

Can you get an old fashioned impact driver in there, the type you hit with a hammer? If so buy a couple of alun key sockets from Halfords of the size you need, buy the proffesional range with have lifetime garentee. That type of impact driver you can get for around £15 ish. Fit key to impact driver, fit to bolt, line it up square and welly with a big hammer. The cast bit will snap before the bolt, that's why you buy with lifetime garentee, take it back and try again untill it's out.
While I have makita impact drivers I still use the the hit it one especially for the applications where too much torque lands you in a world of pain as the makitas will round the socket head before you can let the trigger go.

Paul.