Jvdv23

Hello,

I have a problem. The first five or six threads in my crankshaft to tighten the pulley are gone. I cannot get the bolt to get a grip on the thread. The engine is in the car. I tried to tap it with a M16-1.5 tap but it gets no grip. Because the engine is in the car I cannot give enough pressure to the M16 tap.

Any ideas how I can solve this issue?

Thanks
Joost

Schnell Gelb

Joost,
I think you know the answer ? Choosing between old fashioned Helicoil or Timsert or similar is the easy part. Inserting the coil is also esy. The problem is the procedure to get to that point.
I have recently added some useful links to video of dropping the engine.Sorry.
I hope others can think of an easier solution. Meanwhile ,accumulate a 'while I am in there' list of jobs?
Whatever is suggested, it has to enable you to drill out the damaged threads absolutely in line with the center-line of the c/s.
A hack may be possible if some of the deeper threads are still in good condition. A modified #1 or 2 taper tap(cut down?) may 'search' out the good threads ? Whatever you use it must be absolutely aligned with the old threads.If you use plug tap first , it will be very difficult to start and continue to keep it aligned.If there aer a lot of dbris bits in there use a spiral tp or at least lots of thin oil to flush out the debris as you cut. If you cut misaligned threads you will have no alternative but to rill out and helicoil.
I have a small cheapo borescope attachment for my laptop which I would send down that rabbit hole to observe the problem.
You may see lots of stripped threads from the bolt embedded in the c/s.If you can extract those, it may help. Such work is more like dental surgery than machining or mechanics because you need to use a very sharp, hardened 'pick' to pry out the bits of bolt thread.
If you post some photos, that may encourage others to contribute?
Good luck.

Jvdv23

Thank you for your reply. I am hoping not having to take the complete engine out...

I have added some pictures. You can see the top of the bolt is completely gone (I cut it to try to fit it on the crank).

Macster

With the bolt next to it the tap doesn't look to be the right size/diameter.

You may need to search around but you should be able to find a shorter tap. Be sure you get the right size! And double check its size. Worked in a machine shop for years and at least one time came upon a tap that was mis-marked.

You probably want a bottom tap one that will cut a thread to within (IIRC) 1.5 threads at the bottom. You are not cutting fresh threads but simply cleaning up existing threads.

You will have to replace the bolt.

Jvdv23

Thanks for the reply. The tap seems smaller in this pic but it is M16 -1.5. I can fit it into the hole but it won't get a grip.

is the bottom tap you mention a different kind of tap?thx
joost

Macster

A bottom tap is just a tap that has cutting threads that cut a thread down to about 1.5 threads from the bottom of the hole. There is a taper tap which only has cutthing threads that get to within 6 thread of the bottom of the hole, and then comes plug which gets to around 3 threads of the bottom of the hole. If the hole needs to be threaded "all the way" then one finishs the tapping job with a bottom tap.

As for the tap in the pic being the right size, while I was a journeyman machinist and not bragging but I had a pretty good eye for sizes the tap sure doesn't look to be the right size. But perhaps the picture presents some kind of an optical illusion?

Regardless, my training/experience is to be sure so my recommendation is you need to measure the outside diameter of the tap and check the pitch against the bolt to be sure.

If you are sure the tap is the right size and has the correct thread pitch and you can't get it threaded into the hole then the hole threads are stripped and a clean up using the tap won't help.

You will have to use a thread repair kit of some kind and of course replace the bolt.

Jvdv23

Issue is solved. With a magnet attached a milling machine to they engine and milled away some bad threads.

Schnell Gelb

Thanks for the photo follow up. So often those who beg for help fail to do this .
For those interested in these tools. Yours looks like a Fein?
https://www.milwaukeetool.com/power-...corded/4270-20
http://www.northerntool.com/shop/too...agnetic-drills

So while you have the engine out, what else will you do??

Jvdv23

What would you suggest? I already changed the IMS bearing. Car has 80.000 miles

Schnell Gelb

RMS ?
Because access is so difficult with the engine & trans in the car, almost every maintenance+repair task is easier with them out.
For example, even spark plugs, serpentine belt(because of the 5mm concealed bolt head that spins!), water pump, alternator, vacuum lines, AOS, coolant tank, it is a very long potential list !