Crank bolt keeps coming loose.

Bartly · Jul 20, 2017

Anybody else with a Procharger Stage 2 have their crank bolt come loose? It's happened to me twice now in the 5k miles I've put on it since the install. I've been using a stronger grade 10.9 bolt than the 8.8 grade bolt that came with the PC kit. Figured this would be better because I can torque it down more than the supplied bolt. I've been torquing it to 90 foot lbs and this last time I reinstalled it with blue loctite and just saw its loose again after a couple of thousand miles.

The torque specs I find for 12mm bolts at grade 10.9 range from about 85 ftlb to 105 ftlb. I figured I'd split the difference just to make sure I don't snap the bolt off. I'm thinking about using some red loctite next to around.

Anyone else experience this or have a suggestion.
Thanks

jgedde · Jul 20, 2017

Bartly said:
Anybody else with a Procharger Stage 2 have their crank bolt come loose? It's happened to me twice now in the 5k miles I've put on it since the install. I've been using a stronger grade 10.9 bolt than the 8.8 grade bolt that came with the PC kit. Figured this would be better because I can torque it down more than the supplied bolt. I've been torquing it to 90 foot lbs and this last time I reinstalled it with blue loctite and just saw its loose again after a couple of thousand miles.

The torque specs I find for 12mm bolts at grade 10.9 range from about 85 ftlb to 105 ftlb. I figured I'd split the difference just to make sure I don't snap the bolt off. I'm thinking about using some red loctite next to around.

Anyone else experience this or have a suggestion.
Thanks

This should NOT happen, even with no Loctite.

Loctite can be picky. In your case I presume you're using 242. It's heat range is not the greatest.

Try again using Loctite 246 (Medium strength, high temperature). Make sure both the internal threads on the crank and the external threads on the bolt are spotlessly clean. Spray the hole up with brake cleaner to flush out any stuff and residue in there. Try to brush out all remaining Loctite and goo with a gun cleaning brush. I'd also recommend a new bolt. Does ARP offer anything?

With the red "high strength" stuff you may run the risk of not getting the bolt out if you need to. Only go that route if the 246 doesn't work. I would use 272 in this case. But again, be careful. It can be permanent...

Also, Loctite needs to be fresh. It has a shelf life.

John

TexasGT · Jul 20, 2017

Bartly said:
Anybody else with a Procharger Stage 2 have their crank bolt come loose? It's happened to me twice now in the 5k miles I've put on it since the install. I've been using a stronger grade 10.9 bolt than the 8.8 grade bolt that came with the PC kit. Figured this would be better because I can torque it down more than the supplied bolt. I've been torquing it to 90 foot lbs and this last time I reinstalled it with blue loctite and just saw its loose again after a couple of thousand miles.

The torque specs I find for 12mm bolts at grade 10.9 range from about 85 ftlb to 105 ftlb. I figured I'd split the difference just to make sure I don't snap the bolt off. I'm thinking about using some red loctite next to around.

Anyone else experience this or have a suggestion.
Thanks

How do you know when it comes loose? Just check it often? Or do you feel something in the car?

Bartly · Jul 20, 2017

jgedde said:
This should NOT happen, even with no Loctite.

Loctite can be picky. In your case I presume you're using 242. It's heat range is not the greatest.

Try again using Loctite 246 (Medium strength, high temperature). Make sure both the internal threads on the crank and the external threads on the bolt are spotlessly clean. Spray the hole up with brake cleaner to flush out any stuff and residue in there. Try to brush out all remaining Loctite and goo with a gun cleaning brush. I'd also recommend a new bolt. Does ARP offer anything?

With the red "high strength" stuff you may run the risk of not getting the bolt out if you need to. Only go that route if the 246 doesn't work. I would use 272 in this case. But again, be careful. It can be permanent...

Also, Loctite needs to be fresh. It has a shelf life.

John

I believe the 242 is the red I have. Cleaning the internal threads is a bugger, probably the biggest reason I don't want to use it at all. The bolt should be good as new still, I really don't know why it's happening. The Loctite is really old though and has spent a few years heat cycling in my hot garage, I might need to get a couple new bottles.

TexasGT said:
How do you know when it comes loose? Just check it often? Or do you feel something in the car?

No symptoms I just checked it a couple of hundred miles after the install and it was loose so I retightened it. Found it loose a second time a few weeks later and that's when I put the loctite on. I was checking it every couple of weeks and it hadn't loosened up in a few months. Then reading that thread about the guys crank snout snapping made me look at it this morning and it was probably 1/8-1/4 turn loose, so not much, but not good either.

TexasGT · Jul 20, 2017

Had me worried, so I just checked mine and all good. About 4 months since it was messed with.

Bartly · Jul 20, 2017

TexasGT said:
Had me worried, so I just checked mine and all good. About 4 months since it was messed with.

That's good. I've searched a little and it doesn't seem to be common at all on the S550. Plenty of reference on other engines and older mustangs, even guys with LS engines and 250 ft-lb torque on their bolts. Was half wondering if it has anything to do with the way the blowers crank pulley stacks on top of the OEM pulley.

BMR Tech · Jul 20, 2017

Is the thread engagement different on the PC system?

If not, use a stock or an ARP bolt.

If ARP, make sure it is lubed properly with the ARP specific lube - and torque it to 120ftlbs.

If it comes loose after that, the crank damper is not seated all the way / properly.

Good luck.

BMR Tech · Jul 20, 2017

OH and FWIW.

If a bolt comes loose like this it is a VERY GOOD idea to remove the crank damper and inspect the keyways for cracks.

It could save you thousands. ;)

Bartly · Jul 20, 2017

BMR Tech said:
Is the thread engagement different on the PC system?

If not, use a stock or an ARP bolt.

If ARP, make sure it is lubed properly with the ARP specific lube - and torque it to 120ftlbs.

If it comes loose after that, the crank damper is not seated all the way / properly.

Good luck.

BMR Tech said:
OH and FWIW.

If a bolt comes loose like this it is a VERY GOOD idea to remove the crank damper and inspect the keyways for cracks.

It could save you thousands. ;)

Thanks and thanks. The procharger pulley uses a several cam/bolts to center their pulley onto the factory pulley and then uses a longer 120mm bolt, not sure if the thread engagement is the same. When I re-installed the damper it went on without a hitch and I could tell it had bottomed out. Thanks for the insight on checking the keyway, I'll have to find some time to get a look at that, do the cracks occur on the keyway or the key?

And yep, installing a ARP bolt is the direction i'm heading next.

pxdenial · Jul 20, 2017

I'm gonna check mine tomorrow. You can't use a stock bolt on stage 2 procharger.

sigintel · Jul 21, 2017

Is the procharger SC belt further out on the crank than the stock serpentine?
Further out the belt mounts, the greater the bending moment/leverage.
I thought I had pushed it at 110ftlb clean dry w ARP.
Used brake cleaner and ran bolt loose saturated with cleaner in out a few times and reblasted after. Freakn paranoid used prolly half the can as its cheap.
For comparison, an M12 x 1.5, a lug nut tightened to 120 is experiencing serious wear and that is a pretty freakn high preload that is doable, but you dont have large reserve if your torque wrench is actually running 8-10ftlb high.

Also, Torque to preload result changes slightly with successive retorque depending on bolt finish, any lube used etc.

Where you buy the bolts? Are they black oxide finish and covered in grease?
Bolts from fastenal or mcmaster sometimes have finishes coated with heavier anti H embrittlement grease that may take a second acetone soak after first cleaning to get graase out of surface porosity. Mfgs grease for long term storage compatibility. Over 37-38 hardness in 10.9 is where embrittlement can be found.

Do you have one of the torque test load cells?
They are the shit. Bought off Amazon but Summit has also.
Found my various wrenches were not as repeatable as I thought.
I have old sockets tack welded to scrap metal that I keep in the bench vise for verifying all my various wrenches. Learned cheap parallel beam wrenches are impressively accurate and repeatable.
https://m.summitracing.com/parts/adt-arm602-4

Jay-rod427 · Jul 21, 2017

BMR Tech said:
Is the thread engagement different on the PC system?

If not, use a stock or an ARP bolt.

If ARP, make sure it is lubed properly with the ARP specific lube - and torque it to 120ftlbs.

If it comes loose after that, the crank damper is not seated all the way / properly.

Good luck.

No it's not. The stg 2 uses the stock balancer with their add on pulley. The bolt and balancer don't even need to come off unless doing opg's.

Bartly · Jul 21, 2017

sigintel said:
Is the procharger SC belt further out on the crank than the stock serpentine?
Further out the belt mounts, the greater the bending moment/leverage.
I thought I had pushed it at 110ftlb clean dry w ARP.
Used brake cleaner and ran bolt loose saturated with cleaner in out a few times and reblasted after. Freakn paranoid used prolly half the can as its cheap.
For comparison, an M12 x 1.5, a lug nut tightened to 120 is experiencing serious wear and that is a pretty freakn high preload that is doable, but you dont have large reserve if your torque wrench is actually running 8-10ftlb high.

Also, Torque to preload result changes slightly with successive retorque depending on bolt finish, any lube used etc.

Where you buy the bolts? Are they black oxide finish and covered in grease?
Bolts from fastenal or mcmaster sometimes have finishes coated with heavier anti H embrittlement grease that may take a second acetone soak after first cleaning to get graase out of surface porosity. Mfgs grease for long term storage compatibility. Over 37-38 hardness in 10.9 is where embrittlement can be found.

Do you have one of the torque test load cells?
They are the shit. Bought off Amazon but Summit has also.
Found my various wrenches were not as repeatable as I thought.
I have old sockets tack welded to scrap metal that I keep in the bench vise for verifying all my various wrenches. Learned cheap parallel beam wrenches are impressively accurate and repeatable.
https://m.summitracing.com/parts/adt-arm602-4

Thanks. I've always wanted a way to test my torque wrenches, that tool looks pretty slick. Always another tool to own, I can see that one being handy. Yeah, I've never been super sure how accurate my wrench is, but have been using it on several vehicles for probably 20 years and never broke a bolt. The only other fastener I fought with getting loose was the large nut on my jeeps transfer case outpute yoke, finally solved that with some "permanent" loctite.
Finding torque values for the 10.9 grade 1.5 mm pitch is kind of tough, looking though it appears to be somewhere between 85-105 ft-lbs. I took mine up to 90 just for the reason you described above.

The bolt came from Fastenal, I went with the yellow zinc one. Time for a new bolt.

jgedde · Jul 21, 2017

Bartly said:
I believe the 242 is the red I have. Cleaning the internal threads is a bugger, probably the biggest reason I don't want to use it at all. The bolt should be good as new still, I really don't know why it's happening. The Loctite is really old though and has spent a few years heat cycling in my hot garage, I might need to get a couple new bottles.

No symptoms I just checked it a couple of hundred miles after the install and it was loose so I retightened it. Found it loose a second time a few weeks later and that's when I put the loctite on. I was checking it every couple of weeks and it hadn't loosened up in a few months. Then reading that thread about the guys crank snout snapping made me look at it this morning and it was probably 1/8-1/4 turn loose, so not much, but not good either.

242 is blue...

J

jgedde · Jul 21, 2017

BMR Tech said:
OH and FWIW.

If a bolt comes loose like this it is a VERY GOOD idea to remove the crank damper and inspect the keyways for cracks.

It could save you thousands. ;)

Awesome advice!

Crank bolt keeps coming loose.

Bartly

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