Cylinder head cover bolt - sheared off. ahhhhhhhhhh

[mattye]

Hi all,
Just a note to all to be careful when screwing in the three cylinder head cover bolts. I had just finished the service on my 2014 LC and was on the last bolt when I think the threads crossed and after feeling only a slight increase in resistance 'ping' and the bolt came out leaving about 10mm of the thread left in the cylinder head  >:( >:( >:( >:( >:( >:( >:( >:( . They only gets torqued to 20nm and i was nowhere near that as it was just over finger tight.


Tried to centre punch and drill the sheared off piece out but it seems hard in the centre of the thread so the drill wandered.
I finally contacted a company called 'thread doctors' and they are coming out next Tuesday to have a look at removing the sheared thread with the head on the bike. If not then its a shed load of work to remove the head and then get it to an engineering company to drill it out.
I called my local BMW dealer (North Oxford garage) who didn't seem that interested and just said they would simply send it to and engineering company so i'll miss out the expensive middle man and sort it myself.


Be warned. :kacsint2:

[David.]

They only gets torqued to 20nm

This video, https://www.youtube.com/watch?v=iJEjGm8ne1g and link to JVB, http://www.jimvonbaden.com/Wethead%20Torques%204.pdf, suggest the torque setting is 10 Nm.

[mattye]

Ohhhhh S**********t.  :-[ :-[ :-[ :-[ :-[ :-[ :-[ :-[ :-[ :-[


Just checked your links and the Haynes manual and you are right. 10Nm. Don't know why I had a figure of 20Nm in my head.


Lesson learned. Double check before you tighten anything!

[David.]

Tried to centre punch and drill the sheared off piece out but it seems hard in the centre of the thread so the drill wandered.

Is the bolt sheared off flush with the cylinder head, could a nut/bolt or similar be welded to what's left. https://www.youtube.com/watch?v=aRrz-cphBY4

Applying heat is a trick that sometimes works.

Which bolt has sheared off, one of the two in the centre or the one near the inlet port.

[David.]

This is a cylinder head off a TC, it only has two valve cover bolts in the centre.

[David.]

[mattye]

The LC has 3 cylinder head cover bolts. The one thats sheared is just to the right of the tag in the first cylinder head picture.


The thread is not flush and sits about 3-4 mm below the surface of the cylinder head.

[David.]

I finally contacted a company called 'thread doctors' and they are coming out next Tuesday to have a look at removing the sheared thread with the head on the bike.

If not then its a shed load of work to remove the head and then get it to an engineering company to drill it out.

Hopefully, the sheared thread can be drilled out in-situ & a helicoil fitted.

[SweRT]

Don’t panic. The bolt does not bottomed in the hole why the sheared off piece should be fairly easy to get to rotate with proper tools. Sometimes even an attempt to drill counterclockwise with a reverse drill is enough to grab/give friction enough to get it to start turn out.
Anyhow, I do not think the 'thread doctors' will have any problems to remove the sheared thread with the head on the bike, or as DaygloDavid mentioned, in worst case use helicoil

[Our Gee]

Bad luck "mattye", but looking at the pictures and the info from SweRT that the screw does not bottom out, which the "shoulder" at the end of the threaded portion would suggest, removal should not be a big problem. Aldi have stud "Extractors" at a keen price although I'm not so sure if the smallest would be small enough. To reiterate from a prevoius thread, a friend of mine who works in industrial tightening and tensioning says that more threads are damaged / stripped with Torque Wrenchs than without. My Son in Law recently borrowed one of my Torque Wrenches to "ensure" he applied the correct Honda specified torque value when he reassembled part of his Fireblade front brake caliper. He called me up in a state of distress saying that a bolt had snapped. When we checked the value he had set the torque wrench to he had set it to lbs/ft instead of N/m, just one of the many common and unforgiving mistakes. Anyhow, good luck. I'm sure all will be well.

[mattye]

Hi all,


Quick update. Thread doctors came out today and 20 mins later all sorted. They got the sheared thread out without damaging the threads and the replacement bolt screws in a treat.


Lesson to all. Double check the torque figures before you set you torque wrench.


Cheers for all the message of support. Back to riding 800 miles a week :D

[David.]

Thread doctors came out today and 20 mins later all sorted. They got the sheared thread out without damaging the threads and the replacement bolt screws in a treat.

What method did they use to remove the sheared thread.

Out of interest, may I ask how much they charged.

Are the thread doctors a local or national company.

[mattye]

They flattened off the top of the sheared off fastener. Then drill the centre and then an easy out.
They charged £50 and you can just google 'thread doctors' and then ping them an e-mail. I sent my e-mail in and then i was given the number of a local guy. Very helpful and knowledgeable. I would defo recommend.
Certainly saved me a lot of time and effort and as i've never drilled a thread out before i was more than happy to let these guys do it.