06 EJ25: overtightened TB tensioner bolt, now what?

[v8volvo]

I did something stupid, and changed the T-belt on a family member's 06 OBW without checking torque specs first and without using a torque wrench. Was putting it back together and tightening everything down, and as I tightened the through-bolt for the TB tensioner pivot, giving it one last bit of twist I felt that sickening give of a bolt stretching, or threads being pulled out. Uh-oh.

 

Went ahead and finished the job, since at that point it was just sticking the balancer and covers back on. Car started up and drove out of the garage fine, and has been sitting waiting for me to figure out what to do about it.

 

Bolt felt solid and tight after I removed the tool, and tensioner tightened up fine, but I am uncomfortable. Tensioner was a new one ($$$), I looked at the bolt from the old tensioner and the section that threads into the engine is quite short and the threads are relatively fine... as I was afraid of. Torque spec for this is in the neighborhood of 15-20 ft-lb, as I know now having looked it up after the fact. I'm sure I put twice or three times that amount on it. End of the day and wanted the job done. Now paying the price.

 

Does anyone have any experience with this type of situation, and any ideas for how to resolve without major work? Is there enough room/threads in the hole to use a longer bolt? Heli-coil the only option? Maybe bolt just stretched and can replace with one out of old tensioner??

 

Thanks for any advice or ideas on how to get out of this bind...

[v8volvo]

In seeking out more information about this, I came across the following:

 

http://forums.nasioc.com/forums/archive/index.php/t-950004.html

 

This suggests that part number 13156AA052 can be used to repair stripped tensioner threads, by replacing the bracket the tensioner mounts to, at least for the '97 EJ22 being discussed in that thread. My application charts show the same tensioner being used for virtally all EJ-family engines from 1997-onward, including both that EJ22 and the EJ253 in this '06 OBW. I suppose that indicates that the bracket the tensioner mounts to is probably the same, too, and is correct for this application as well.

 

Bracket is available for less than $35. At that price it is well worth going back in and re-doing it right. Seem likely that this will be compatible? Would much rather replace this bracket than wait and have the engine blow up a few miles down the road.

Edited April 10, 2011 by v8volvo

[bheinen74]

aluminum threads will give out before the bolt does..

Edited April 10, 2011 by bheinen74

[logic23]

dont sweat it too much... the tensioner is threaded into a bracket that can be replaced. its held in place with 3 12mm headed bolts. they are the same from 96 up. I might have one that I can send you. take a pic of yours and we'll see what we can do.

You can also put a helicoil in the stripped threads.

I wouldn't leave it the way it is now ......too big of a risk.

[987687]

I've stripped the threads in that bracket before. The threads actually came out with the bolt when I took it apart. A trip to a machine shop and $15 later I had it heli-coiled. Not really a big deal.

[ShawnW]

I can ship you one Priority Mail/Fedex.

[idosubaru]

bracket is easy, nice to see they're inexpensive.

 

like mentioned the threads fail, not the bolts.

 

if you chase the threads on the bolt and the bracket with a tap they may be fine. i didn't hear any talk of metal shavings or bits coming out with the bolt, so sounds to me like it's fine. might be worth saving as a back up for next time.

 

i would check that torque value 15-20 pounds sounds too little?

[Gloyale]

That holes is pretty deep too. You could use a 5mm longer bolt for a quick fix.

 

Otherwise remove the bracket and helicoil, or just replace with a new one.

[Fairtax4me]

Alot of people forget that aluminum is a very soft metal. The threads more than likely are pulled out of the bracket.

 

Take the bracket off and clean it up and see how much thread if any there is that is still usable. If you have about 10mm of good threads past the stripped part just get a longer bolt and use the correct torque spec.

[987687]

On mine there were so few good threads left it wasn't worth risking it. But mine came out with the bolt...

 

IIRC the torque spec is somewhere around 30 - 35 ft/lbs

[v8volvo]

All fixed, with a new bracket. As I was taking it apart, the tensioner bolt actually felt fine as it loosened up, and threads looked good. Probably would have been fine after all, but I already had a new bracket so put it on and put it all back together. Better to have the peace of mind anyway -- even if all looked and felt good now, that little bit of give I felt when tightening was reason enough to re-do it. For my $26, new bracket is a faster/easier/better solution than a longer bolt or heli-coil.

 

The threads are relatively fine on that bracket and could easily have failed if overtorqued. The bolt does not go particularly deep into them, either, so the thread contact area is not that great. All good reasons to not overtorque it.

 

I torqued it to 18.5 ft-lb according to the specs I found. Other idlers torqued to 29 ft-lb. The tensioner through-bolt really should not see much force, since the tensioner's pivot point is quite far away from where the roller contacts the belt and where the hydraulic piston puts its opposing force on, so the lower torque value for that bolt makes good sense.

 

Felt much better about the finished product second time around. Was even faster the second time -- whole job was barely an hour and a half start to finish, done without removing rad or fans, and including replacing the bracket and compressing the tensioner! Thanks to all for the advice. Subie is happy and ready for its next 105k miles.