Repairing a thread without removing the sump?

[Casar66]

After I had fitted the sump I went over it with the torque wrench. Unfortunately, one thread at the rear towards the gearbox did not survive. The thread is cut in aluminum.
Can I repair this with a helicoil without having to remove the oil pan again?

Edited January 28 by Casar66

[mleadbeater]

Torque wrenches can be dodgy on this type  application, and should in my opinion be avoided , just “ feel “ should suffice. 

They are very inaccurate and subjective, ie lubricant on the thread, condition of thread, etc.

Anyway , to answer your question, I would say a helicoil in this application with sump in place would mean drilling an oversize clearance hole in the sump flange first, to clear the tap, then the thread could be cut in the crankcase with the sump in place.

Would any swarf go into the engine? or is the hole blind? I am not that familiar with this engine, just my general thoughts.

Could an oversize bolt be used? , maybe go to a coarser thread, eg UNC. or metric?

The XPAG engine in my TD , of French design (Hotchkiss), has sump and other bolts tapped  into  the iron and ally block and covers etc, using metric fine M8 threads, a  very poor engineering practice in my view, many owners report stripped threads.

Hope this helps, I may have this issue when I replace the thrust bearings. 

Good luck

Mike

Edited January 28 by mleadbeater

[RogerH]

1 hour ago, Casar66 said:

After I had fitted the sump I went over it with the torque wrench. Unfortunately, one thread at the rear towards the gearbox did not survive. The thread is cut in aluminum.
Can I repair this with a helicoil without having to remove the oil pan again?

Basically - no.

As stated above the sump pan flange would end up with an over size hole that may be awkward to hold down.

Take the sump off and then know you have done it properly

Roger

[Casar66]

Unfortunately the hole is not blind. That worries me. 

I'm particularly worried about the small extension of the helicoil insert, which has to be chiseled away. 

[RogerH]

1 minute ago, Casar66 said:

Unfortunately the hole is not blind. That worries me. 

I'm particularly worried about the small extension of the helicoil insert, which has to be chiseled away. 

Nothing should be chiseled away. The small tang simply breaks off.

 

Roger

[Casar66]

1 minute ago, RogerH said:

Basically - no.

As stated above the sump pan flange would end up with an over size hole that may be awkward to hold down.

Take the sump off and then know you have done it properly

 

Should'nt the washer and the srew's head big enough?!

[RogerH]

1 minute ago, Casar66 said:

Should'nt the washer and the srew's head big enough?!

I don't think so>

 

Roger

[Casar66]

10 minutes ago, RogerH said:

Nothing should be chiseled away. The small tang simply breaks 

 

Regardless of whether you chisel it away or break it, there is a remnant of the helicoil that should not fall into the oil pan.

 

Maybe I should just glue the original screw in with epoxy. Removing the oil pan is not a solution in view of the workshop situation. I won't do it a second time.

I'm open to any ideas.

 

Edited January 28 by Casar66

[Motorsport Mickey]

" I won't do it a second time."... so that's your decision made.

I'm open to any ideas.

After you've opened up the sump hole to allow the drill and tap to pass through it to remake the thread Tie a length of fishing line to the helicoil tang and carefully wind the helicoil into the block and when fully inserted use long nose pliers (if small enough) to reach into and break the tang off and withdraw it. If the hole is to small for your pliers, use a screwdriver and press down onto the helicoil tang and snap it off and withdraw it with the fishing line. If it doesn't work you still have the sump removal you can do.

Mick Richards

[Casar66]

Thank you. I have an artery clamp that I usually use for the pin on the door handle

 

[Steve 286]

The two centre rear bolts should be blind I have fitted helicoils in this location without any problems with the sump in place the two front bolts go straight though which you need to be careful with I use ground down thin nose pliers to remove the tang

[Casar66]

That sounds too good. Are you sure?

[Steve 286]

If you look at the rear cover where the bolts fit there are two humps which stick out towards the flywheel if you poke a small screw driver in the holes it should only go in by about 15/20 mm 

[Steve 286]

If you look up rear main seal cover you will see  what I mean I tried putting a picture on but was unable to the humps are the same both sides





 

[Steve 286]

I forgot to say the bolt holes in the sump are bigger than the helicoils 

[Casar66]

Getting better and better

 

[mleadbeater]

Just a thought; is there any good thread further up inside  the hole, into which a longer bolt could engage.

Does this bolt need to be very tight?

If you used sufficient gasket sealer, these bolts don’t need to be super tight, as long as they nip up the gasket they should be fine, indeed over tightening can cause the flange to distort and cause leaking. 

Thats why I wouldn’t use a torque wrench myself, just nip them up sufficiently to get the sealer to begin to squeeze out. They are not structurally resisting any forces, eg oil or gas pressure , or bearing forces, just holding on the sump and contents.

Some thread lock would ensure they didn’t work loose, maybe check periodically for any leakages. Silicone sealer will set, and retain a seal almost indefinitely.

Mike

[BlueTR3A-5EKT]

Here’s a bodge.

Drill the hole deeper to tapping size for 5/16 unc.  Tap the hole 5/16 unc    Screw in 5/16 stud that junction one end and unf the other.  Retain sump with nut and washer.    It is what we do on the aluminium sealer block at the front of the wet liner engine.

[charlie74]

I’m pretty sure I did this repair with the sump in place.  What I did more recently when I rebuilt my engine was used exhaust manifold studs in the holes (in the installed helicoils) and set them in place with thread lock and nuts and washers to secure the rear of the sump.  Not sure if you can do this with the engine in the car and the sump in place but I think its a good repair.

 

[KiwiTR6]

I encountered this same problem after removing the sump to check crank end float and seal several open stud holes that were creating oil leaks.  Made the mistake of torquing them all on refitting and pulled a front alloy block thread.  Being the lazy person I am, I made up a stepped stud from the next size up bolt by turning half of it down and cutting the standard thread so it appears normal.  I used grease on the tap (although I'm pretty sure I'd already sealed the blind hole from the inside) and from memory the tap may have slightly enlarged the hole in the sump as it made it's way through.

Anyway, it was reasonably simple and effective.  I've attached the only two photos I took of that job.

[Casar66]

thank you so far, guys.

Good to know that I am not the only rough locksmith here. What really pi--es me off is that I would never had tightened the screws that far. But I want to do it 100% so I use the torque wrench (which normally never use apart of very critical "operation", always trusted my wrist)

Anyway, now I habe some options for repairing. If it is possible I would just repair the thread and use the original screw. 

[JochemsTR]

Since the sump is in place, I am not sure how you can drill and tap anything. There is no room for the tooling to turn. 
my suggestion: glue the damaged screw in place and fix properly next time you remove the sump. 

Edited January 29 by JochemsTR

[Casar66]

Yes, that worries me indeed. But it is aluminium and not steel (if the hole in the sump is big enough). So I hope with some dirty trick...

[Z320]

Or glue a bolt in with loctite strong and use a nut,

as Charlie74 recommended above. Quick and easy?

Edited January 29 by Z320

[Steve 286]

If you want to do a 100% job I would helicoil I extended a drill bit to make it easy and use a socket and extension bar on the tap for recutting the thread for the helicoil I have done this many times for my own car and other peoples once fitted I’ve never had one strip it does Make them stronger once you’ve done one and you know what you’re doing it’s only a 30 minute job just make sure the helicoil is not too long as when fitted the coil grows longer due to the way it goes into the thread you cut hope  this makes sense