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Fixed Stripped Thread. Hopefully Nobody else has to do this...

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130
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14
Location
Milpitas, CA, USA
#1
Got around to fixing the stripped threads on my engine block for the passenger side engine mount. It was a PITA, but not impossible. Definitely wouldn't be as difficult with the right/better tools...

Putting this together in case anyone else has issues, but I'm probably one of the only ones because I was stupid with the Mishimoto OCC emptying process. Aluminum also has no fatigue limit and these threads are probably cut and not rolled. This means torquing it on and off is bound to lead to what happened to me (although my problem is more because I cross threaded).

Tools used:
Socket wrench - 18 and 15mm deep sockets
Torque reader (torque wrench works too)
Cordless power drill (Careful with this one, more on that later)
Timeset thread repair/insert kit (has a custom tap, counterbore, drill bit, and thread former) (link)
Tap handle/wrench
Floor jack
Wood block
Shop vacuum
Screw drivers (philips and flat (or torx)) for headlight removal.


Consumables used:
Timesert thread insert (M12 x 1.75 x 16.5 mm)
Motor oil (used it as cutting oil)
Loc-tite
Towels

Nice to have, but I didn't:
Extra engine coolant
Drill bits that are a tad smaller than the provided one in the Timesert kit.

DISASSEMBLY/PREP STEPS:
  1. Pop off the plastic engine cover
  2. (if Mishi OCC) disconnect hoses to the OCC
  3. With a floor jack and the wooden block on it, carefully raise the engine slightly. I put my car on jackstands and removed the FR wheel because that was the only access point I had with my floor jack.
  4. Remove the FR headlights. There are youtube videos like this one, but it's removing 2 screws and one plastic screw+insert.
  5. Disconnect the pressure return (I think that's right) line to the coolant reservoir. It's the top line that's semi-rigid and smaller than the others.
  6. Remove the engine coolant reservoir from its mounting tabs. If you have enough extra coolant, I would recommend draining at least half of the reservoir. I got away without draining (no coolant on hand) and set it carefully where the headlight would have been. This, of course, led to some coolant spills.


  7. Remove the 3 nuts holding the passenger engine mount in place. Don't worry if the threaded stud comes out too.
  8. Remove the 3 screws holding the engine mount to the frame. These have washers that are stuck on them, fyi.
  9. Lift the passenger-side engine mount out from the car.

The damage....



TIMESERT INSTALL:
  1. Before starting, I highly recommend having some sort of pan under these thru holes. You're going to create a lot of aluminum shavings. Conversely, if you cant make a stable mount/support for this pan, you'll probably launch your shavings everywhere, which is what happened to me numerous times. You can probably just follow the Timesert install instructions for this part.
  2. Here's the tricky bit. Drill out the questionable hole using the provided drill bit in the Timesert kit (reference the included instructions). BE CAREFUL HERE IF YOU HAVE A CORDLESS DRILL. The A/C line is conveniently in the way of all of the nuts/bolts. You might need the taphandle here because of this ([:(!] more on this at the end).
  3. With a tap handle and the provided counterbore bit, cut out the counterbore until the tool stops. There's a flat lip that should prevent you from going too far.
  4. With the tap handle and provided thread (note that this is custom thread size made for inserts, and can't be used elsewhere), cut the threades into the hole that was just drilled+counterbored. USE CUTTING OIL. I forgot and got lucky that it didn't cause much damage.
  5. Now put in the insert! If you've done the previous steps correctly, you should be able to thread the insert with ease, almost all the way, by hand.
  6. With the tap handle, thread forming tool, and cutting oil/lubricant, form the insert into the hole for permanent installation. I started the beginning by hand until it stopped, then used the tap handle to finish cold forming the last threads. This is where the holding/permanent fixing happens.
  7. Test out your workmanship! Thread in the stud by hand and make sure it goes in easy. Don't cross-thread it again or you'll be screwed...


RE-ASSEMBLY:
Do all the disassembly/prep steps in reverse.
For the torque specifications, use the below. Thanks [MENTION=9]rodmoe[/MENTION] for putting this out there. Literally the only place that has this information listed...
PASSENGER SIDE. (engine mount) 3 Frame Bolts Tq 80 NM (60 ft lbs) 3 Engine Nuts Tq 48 NM (35 ft lbs)





Frustration about the drilling and A/C line:
Throughout this whole process, the almost rigid A/C line obstructed just about everything. The drill bit was quite a step up over the original hole size, so when I drilled the hole, it caught. No big deal, except the A/C line is exactly where the trigger on is located and positioned just right to catch it. This meant that when that cordless drill snagged, it pushed itself over the A/C line, stalled, and almost burned itself out (there was some smoke). Luckily the tap handle I had used a good sized lever arm and Aluminum is soft. Ended up somehow finishing the hole by hand.

Not only that, but the hole is perpendicular to the flat face, and a little askew to relative to the car. I noticed this because the studs definitely weren't parallel once all was said and done. Likely exacerbated by the freaking A/C line in the way and the bad hand drilling.

Other side notes:
I had ordered a Fumoto F-110N ball valve for engine oil drain plugs. This has the 3/8's NPT end that Mishimoto's OCC uses. As I was about to reinstall the whole assembly, I found that the mounting bracket was also broken [sad]. I have the rev 2 version, but I was too tired/didn't want to install at the time. Also semi-questioning the choice to frame mount instead of engine mount, though the flexible hoses should mean this isn't an issue.

It's a cheaper alternative to Mishimoto's plastic drain kit, and the Fumoto valve is brass+stainless. Plus it's on Amazon so Prime shipping if you have it. The valve fit sub-flush inside the can so it shouldn't have much issue draining entirely, but I won't know.





 


Quisp

1000 Post Club
Messages
1,118
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402
Location
Davenport
#2
I almost cross threaded mine. Definitely going with drain valve. I've been removing the allens from the canister but that's a pain.
 


Messages
154
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49
Location
MELBOURNE
#3
Is the torque spec for that bolt really 60 lb/ft? That is actually right at the limit of a 12mm 1.75 thread bolt, and that is going into something a bit more solid than a thin aluminum flange.
 


OP
C
Messages
130
Likes
14
Location
Milpitas, CA, USA
Thread Starter #4
Is the torque spec for that bolt really 60 lb/ft? That is actually right at the limit of a 12mm 1.75 thread bolt, and that is going into something a bit more solid than a thin aluminum flange.
From all the specs I've seen, 60 ft lbs is the torque rating for the engine block. IIRC, Mishimoto said to torque to 60 ft-lbs for installing the v1 bracket. Not sure what grade stud they're using, but that can change the torque limit. In this case, the Aluminum block is really the limiting factor so I have no clue if it was spec'd correctly. I have no access to service manuals either.

Fixed the link above so it goes to the page with rodmoe's post.
 


OP
C
Messages
130
Likes
14
Location
Milpitas, CA, USA
Thread Starter #5
Is the torque spec for that bolt really 60 lb/ft? That is actually right at the limit of a 12mm 1.75 thread bolt, and that is going into something a bit more solid than a thin aluminum flange.
From all the specs I've seen, 60 ft lbs is the torque rating for the engine block. IIRC, Mishimoto said to torque to 60 ft-lbs for installing the v1 bracket. Not sure what grade stud they're using, but that can change the torque limit. In this case, the Aluminum block is really the limiting factor so I have no clue if it was spec'd correctly. I have no access to service manuals either.

Fixed the link above so it goes to the page with rodmoe's post.
 




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