Timing chain damper lower bolt socket stripped

I found out that the lower bolt socket on my timing chain damper is stripped. It is located just above the crankshaft position sensor wheel in the engine block.


This is the bolt:



I verified it is the socket and not the bolt by trying it in the other socket. I also measured the socket with a caliper to make sure I'm not trying a wrong size bolt (which I first thought because a lot of bolts came off this thing). It's a 12 mm bolt, the threaded part is 8 mm in diameter. The same kind of bolt goes in the upper damper hole, which is in the left cylinder head.

I tried cleaning the socket with wd-40, carb cleaner, and a small wire brush, all to no help. I have not yet tried Heli Coil.

I was curious what my options are at this point. I have heard different things about Heli Coil and that it could be risky. I certainly hope to not have to take the block out for machining.

 

Ouch. Have you tried running a tap through it and another bolt and see if it holds at the specified torque?

If not, looks like you'll be removing the timing cover again or oil pan to drill it out and use a heli coil.

OR

*** The procedure was done on a personal vehicle and it worked for me. YMMV ***

Instead of having to tear anything back apart, coat the drill bit in thick, sticky grease and go VERY slow. Allow the shavings to get stuck in the grease, clean and repeat.

 

I don't understand what you mean by this

 

Run through with a tap. This will clean and correct the threads. Then put a same sized bolt in the hole, torque it to factory specifications and see if it holds. If so, you're good. If not, you're going to be drilling and installing a heli-coil.

 

so I should get an 8 mm tap ?

 

8x1.0 or 8x1.25? There is two different thread spacing on 8mm bolts.

Got a thread gauge? You prolly got a 1 or a 1.25 for a 1.25 or 1 hole. Check threads.

 

I don't have a thread gauge. I don't see what the point would be in threading this hole differently from the other one that supports the damper. But if someone can confirm out of the spec (e.g. @1MK) , that would be helpful.

 

16mm x 1.50
14mm x 1.50
12mm x 1.25
10mm x 1.25
8mm x 1.25
6mm x 1.00

 

So are you saying that the two bolts that support this damper (and their holes) are the same, which is what I thought ?

 

Just posting the thread pitch for different size bolts on Toyota's.

All 8mm fasteners are 1.25

 

do you have explicit specs for this particular hole ? I'm trying to rule out that I'm not using a wrong bolt (highly unlikely)

when you say 8 mm, do you mean the threaded part diameter, which in this case is 8, or the size of the head, which in this case is 12 ?

 

8mm is the shank size. The round part.

1.25 is the thread spacing.

 

A helicoil is usually stronger than it was originally. Just don't lose the installation 'tang'.

 

what ?

 

The teeny piece on the end of a helicoil. It's meant to be broken off after installation of the helicoil. It's very hard steel and doesn't play nice with gears etc.

 

An 8-1.25 tap cleaned it out