help with pulled stud

[cord68]

I need some advice on temp fix for this pulled stud, this stud as you can see by the picture come from behind the oil cooler top bolt on 2.7L it’s a 7R case the problem I have is oil was pissing out of this bolt I tried to reseal with new o’ring and sealant but I could not even get 20ftp tension on it. It just keeps pulling the stud out as you can se by second picture how can I fix this without pulling the motor to pieces as a temp fix that will last for 12 months till I can afford a rebuild.

[Porsche_monkey]

So you pulled the heli-coil out?

[cord68]

hi
yes that is what looks like a heli coil in the second photo even with the heli-coil out and you try scew the stud back in it feels tight i dont feel confortable running a tap in that fair and having **** left in the engine but i cant think of any thing else.

[Porsche_monkey]

I'm not sure how the threads could be tight if the heli-coil is gone, but you need to start by trying to instal a new helicoil, with red loctite on it. It probably won't work, but try it.

Then loctite the stud in.

You will likely have to instal a time-sert, which is basically an oversized helicoil.

[sms1305]

That stud looks exactly like mine did. I put a magnet on it to see if it might be a helicoil, but it wasn't magnetic. I would think that if it is a helicoil it wouldn't shatter if you just pinch it with your fingers. That's what happened in mine. Good luck!

[Porsche_monkey]

Well if it's not a helicoil it is the remainder of the thread, and it is magnesium. That happened to me on my 2.7 rebuild.

So now you need to helicoil the hole. It's not that hard, just be sure to drill straight.

[Porsche_monkey]

Well if it's not a helicoil it is the remainder of the thread, and it is magnesium. That happened to me on my 2.7 rebuild.

So now you need to helicoil the hole. It's not that hard, just be sure to drill straight.

[Grady Clay]

The first picture shows the two studs under the oil cooler – with
one missing. Those are case halve fasteners that straddle the
#1 main bearing. The two studs are threaded into the 1-2-3 half
of the case.

One thing I note is someone has used a regular nut. These are
supposed to be cap nuts. Oil will simply spiral down the threads
and leak. I suspect someone tried to tighten them too much to
stop the leak and pulled the threads.

A major issue is the space between the body of the stud and the
case is used to carry pressurized oil to the main bearing. This
stud feeds the #1 main bearing and then to the internal
passages in the crankshaft to the rod bearings. you won’t be
able to Helicoil without getting chards in the passage that feeds
the #1 main and the rod bearings.


(C) 2003 Wayne Dempsey, How To Rebuild & Modify Porsche 911 Engines

Here the red arrow is the passage feeding the #1 main bearing.
The violet arrow is the through hole for the now pulled stud.
Note that the two intersect.

Short answer; I don’t see how you can Helicoil this without
contaminating the oil system. The case has to come apart.

Best,
Grady

[Porsche_monkey]

I did not realize it was that location. Sadly, Grady is correct.

Any fix without disassembly will be high risk. If you want to take the chance re-post here, there are some things you can do to minimize the risk.

On the upside, you'll be able to fix your engine for good when you helicoil/timesert everything.

[HKZ Bob]

Grady Clay
very good analysed.

bob

[captek]

You could try a good epoxy,just keep the threads bone dry and put a two part epoxy on the treads and then put a heat lamp on it for a few hours.This would be the last resort before you have to tear it down and do it right.I have used some of 3m epoxy and it gets so hard you can drill and tap it,it also bonds well to aluminum.Captek

[Grady Clay]

It would be instructive to see possible solutions other than a complete teardown.

There is nothing wrong to have suggestions and submit them to questions. That is what a “discussion forum” is all about.


While I’m not recommending this, how about filling the oil passages with grease, performing the machine (threading) operations and then clean out the grease? I wouldn’t do this without more considered argument to my satisfaction.

Let’s hear more.

Best,
Grady

[911quest]

You could possibly take an case saver or threaded inserts thread it onto you stud cut the insert into a tap fashion and use the insert as a tap and torque it down this is just a suggestion and a very poor way out but it will work they used to do this on old VW motors that would pull the studs out of the case

[cstreit]

One misplaced chip though could cost you a main bearing or worse yet a rod bearing failure... Think if the thing jams into a crank journal?!

I can't come up with any clever solutions. I suppose you could loctite/bondo/epoxy the thing in there, but I wonder how much toque you could safely get on that stud and how important the torque around the main bearing is. Would one thru-bolt under-torqued allow movement in this critical area? I dunno.

Makes me nervous though. (but then so does a double espresso)

[cord68]

Hi
Guys thanks to everyone for the suggestion and tips I tried to re heli-coil that wasn’t an option since the tap to clean it out is bigger than the hole I new this was an oil gallery so I wasn’t game to be putting **** in. I also tried loctite bond which goes off like steel but because of the depth I could not clean properly so it didn’t hold, so I phone a friend at a nut and bolt shop and they made a bolt 160mm long 11m diameter with 1.5 pitch and machined the center of the bolt back to the 8mm the same size as the stud I was able to bolt this back up with pretty good torque. now with everything back on the engine and running it seems to work I have no oil leek but for how long is any ones guess I will monitor over next couple of weeks and let everyone no how its going.

[cord68]

Originally posted by Grady Clay
The first picture shows the two studs under the oil cooler – with
one missing. Those are case halve fasteners that straddle the
#1 main bearing. The two studs are threaded into the 1-2-3 half
of the case.

One thing I note is someone has used a regular nut. These are
supposed to be cap nuts. Oil will simply spiral down the threads
and leak. I suspect someone tried to tighten them too much to
stop the leak and pulled the threads.

A major issue is the space between the body of the stud and the
case is used to carry pressurized oil to the main bearing. This
stud feeds the #1 main bearing and then to the internal
passages in the crankshaft to the rod bearings. you won’t be
able to Helicoil without getting chards in the passage that feeds
the #1 main and the rod bearings.


(C) 2003 Wayne Dempsey, How To Rebuild & Modify Porsche 911 Engines

Here the red arrow is the passage feeding the #1 main bearing.
The violet arrow is the through hole for the now pulled stud.
Note that the two intersect.

Short answer; I don’t see how you can Helicoil this without
contaminating the oil system. The case has to come apart.

Best,
Grady

the answear to your question about the nut is i changed them because it seem to be bottoming out in the acorn nuts but i didn't even consider the oil comming thru the thread,but with new o'rings and and a sealant hopfully it want happen.

[Grady Clay]

Good for you, I hope the solution works.

Did you note how much torque was applied?

When the acorn nut was bottoming out, the reasionprobably was
the stud was already pulling. Did you reinstall the acorn nut or
are you just reluing on sealant? If you need more clearance so
the acorn nut doesn’t bottom, a good solution is a thicker
washer for the O-ring. The limit there is clearance to the oil
cooler.

Whan a mag-case cylinder stud starts to pull, the first clue usually
is the 10 mm Alllen wernch no longer fulley engages the hex in
the nut.

With your custom stud, the 8 mm diameter in the area of the oil
passage (red arrow) is necessary. There needs to be suficent
clearance for the oil to get past the stud and feed the #1 main
bearing and the rod bearings.



I know you realized this but I didn’t want someone in the future
to install a completely 11 mm OD stud.

Best,
Grady

[justinp71]

So is it leaking? Can you tell us where you got that stud from?

[DohertyCM]

Why would you put a helicoil back in? They are junk for engines and such, go with something better. A helicoil will just pull out again. We use them in aircraft but only on parts that dont have a stress load associated with it because it will pull out.
Personally I would get it fixed right so you wont damage other things as a result. But that is just me.