Threads must be made of butter

[Gpruitt54]

I am trying to install a starter on a 2010 Subaru Legacy (one of the easiest projects you can do on this car short of changing a tire). As I was re-installing the long bold (see photos), I turned the bolt in by hand 1/8 of a turn the bolt grabbed a thread and just got harder to turn. I backed the bolt out and found shavings on the bolt. The starting threads on the bolt was goofed up. Thinking that I had cross threaded the bold, I put a tap on the bold to clean up the threads. Getting the bolt started was still tough, but easier than before. WTF!

 

It seems that the bolt hole threads are crossed. I have taps and dies, but the taps are not long enough to reach the threads in the block. I am putting oil on the threads of the bolt and giving the oil a change to clean out the threads, as if I was using a tap. The photo of the bolt is how it looked after my last session of gently easing the oiled bolt into the bolt hole threads.

 

I know I should be using a tap, but standards taps are not nearly long enough for the depth of the threads at this location. Amy suggestions? Is what I am going making things worse? Just trying to get this thing done, but the car is fighting me every step of the way.

 

 

Edited May 4, 2021 by Gpruitt54

[creep_nu]

that's an aluminum block for ya. on my old outback i stripped out one of the water pump bolts torqueing it down to the required value(like 8 ftlbs or whatever)...pulled the bolt and the entire threaded section came out.

 

if you want to fix this properly you need to remove the transmission and install a helicoil in the block, then reinstall transmission. if you were able to get it in decently, just leave it for the next poor fellow.

[Gpruitt54]

Well, the starter is installed and working. To get this job done, I continued to run the oiled bolt in until the threads got stiff. I then turned the bolt a quarter turn, then ran it out several turns. Repeating this process until eventually reached a point there I would get the bolt tight against the starter mounting flange. So, essentially, I used the bolt as a tap. It worked thank God. Hopefully, I won't have to replace the starter again.

[Scubaboo]

Ooof. You got lucky with that one. Would have sucked to pull the transmission to fix a bolt hole.

[Gpruitt54]

Ooof. You got lucky with that one. Would have sucked to pull the transmission to fix a bolt hole.

 

Lucky? Heck yeah! For whatever reason, the bold did not show signs of massively chewing up the threads. I blew out the hole with compressed air, expecting all kinds of metal shavings to come out. But nope. I still cannot believe how easy the bolt hole cross threaded.

Edited May 6, 2021 by Gpruitt54

[ibr_adam09]

I would've wrapped the bolt threads with plumbers tape and then some jb weld (or this https://www.amazon.com/MASTERCOOL-90934-Alum-Repair-Epoxy/dp/B00AZJTEAS/ref=asc_df_B00AZJTEAS/?tag=hyprod-20&linkCode=df0&hvadid=312148135388&hvpos=&hvnetw=g&hvrand=12975232972507960263&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9011806&hvtargid=pla-526872972600&psc=1). This way you can 'fix' the internal threading once you tighten and let it hardened.

[DrD123]

I think the jbweld approach has a non-zero chance of going horribly wrong... weird that the threads were binding - I am guessing debris of some sort got in there if when it was first removed it came out without incident...

 

 

 

Gradually running the bolt in there (with known good threads) like a tap with something to lubricate the threads as was done here is probably the safest approach - the steel bolt is always going to win against the aluminum threads, so taking your time and running it in straight by hand is what I would have done, as well. Only additional step I would have probably done is to try and clean out the hole to remove any potential debris - getting the tube in there from a can of brake/parts cleaner and flushing it out thoroughly

[Gpruitt54]

I think the jbweld approach has a non-zero chance of going horribly wrong... weird that the threads were binding - I am guessing debris of some sort got in there if when it was first removed it came out without incident...

 

 

 

Gradually running the bolt in there (with known good threads) like a tap with something to lubricate the threads as was done here is probably the safest approach - the steel bolt is always going to win against the aluminum threads, so taking your time and running it in straight by hand is what I would have done, as well. Only additional step I would have probably done is to try and clean out the hole to remove any potential debris - getting the tube in there from a can of brake/parts cleaner and flushing it out thoroughly

 

Good idea to clean out the hole with brake cleaner. I should have thought of that myself. The closest I came to cleaning out the hole was compressed air to blow any debris out of the hole. I pulled the bolt out completely many times to inspect the threads and to apply more cutting oil. I also used a Sharpie and drew a line down the non-threaded part of the bolt. This was to determine if the bolt was starting to twist. This was a scary project, with the possibility of snapping the bolt top if mind. Thank God it is done without mishap.

[poconoracing]

Glad you got it handled. You did the right thing .., patience works wonders.

 

Odds Re there was aluminum corrosion on the threads in the hole. Happens more often then you think in The bellhousing bolts and the head bolts.

 

A trick I’ve used is take one of the old headbolts and cut a grove down the threads with a cutoff wheel on each side, or three if you are ambitious. And use the cut bolt as a tap. The groove gives the material somewhere to go. Then same as you did, oil, turn it in until it starts to bind, back it out and clean off the grime. It would work in your situation as well. You could actually use the grooved bolt if you like, or replace it.

 

Lastly use a bunch of neversieze on the end of the bolt to coat the threads, and hopefully prevent a future problem.

Edited May 21, 2021 by poconoracing