Stripped injector hold-down threads on OM611 engine

[rockbeer]

Well, the title says it all.

Had to extract no.1 injector to cure a severe case of injector seal leakage. When I removed the bolt, half the internal thread from the bore came out with it.

Any ideas or advice on how to get this sorted?

Looks to me like a case of drilling out the bore a few mm oversize and putting a thread insert in there. Trouble is I don't have the tools or skills for it. And I really don't want to pull the head unless I absolutely have to, so could really do with finding someone who not only knows what they're doing and has the right tools, but who is prepared to do the job al fresco on a Hackney side street.

All suggestions gratefully received.

Cheers,
Bruce

 

[jaymanek]

Yes you need to have it re threaded. Id speak to some of the local garages as they will know someone with the correct tools.

 

[murray motors]

you have about 3 inches of bolt hole and 1 inch is threaded use the first 2 inches that arnt threaded.Use an M9 x 1.5 allen key bolt and M9 x 1.5 tap m9 is very hard to come by we use a M10 x 1.5 its a bit tight you will need to drill out the clamp this is not for the faint hearted

 

[rockbeer]

Thanks to you both for the input.

I think I may have located somebody locally who can do this work, although I would have a go myself if I thought I could get it right. My concern with tapping the thread is getting the tool dead square into the bore. Are guides available to help with that?

murray: do you find that your method creates a lasting repair? The MB bolts are stretch-type - do you just use a regular bolt instead?

Cheers,
Bruce

 

[proser]

Mines had that type of repair on one of the bolts and hasn't caused any problems in all the time of had the car.

 

[rockbeer]

I can source an M9 x 1.25 tap and bolt - wondering whether this would be OK to use or if it has to be M9 x 1.5? Why??
Thanks again,
Bruce

 

[rockbeer]

Another question if you all don't mind:

Why would I not tap the 8mm upper section of the injector hod-down bore with an 8mm thread and use an M8 bolt?

I measured a 3/8 BSW tap (closest to hand) against the hole and that looks like it will barely fit. I don't see how I'd ever get a 10mm tap down there. And M9 bolts are all but impossible to find.

Curiously,
Bruce

 

[murray motors]

an M10 is just that bit to thick M9 is just right but hard to get M8 is to thin doesnt matter what pitch we use 1.5 as it easy to get do a dummy run you might need to get a couple off diffrent lenths of bolt we use 8 mill allen key bolts black strong ones if deep enough you can swing on these were you cant swing on a merc bolt john

 

[rockbeer]

Thanks Murray, that's so helpful. I'm pretty much decided to have a go at this repair myself - even if I make a hash of it I'll still have the option to go to an engineering shop for a Timesert treatment as plan B. I'm going to try reaming out the hole (really slowly and carefully) with an 8.8mm drill bit to make it accept a 10mm tap properly. I think it should be OK if I use a really sharp drill bit, and do it by hand rather than with a power tool.

So:

What length bolt would you recommend?

And, do you tap the entire section of the bore, all the way down to where the 6mm thread starts?


I will do some trials first. A drill guide would be very useful. Any ideas on that?

Thanks again, this is really helping me out.

Bruce