M8 sheered in cast exhaust manifold - technique?

[julianf]

The last time this happened to me, I made a mess of it. I drilled, then used too small a stud extractor, which then snapped and I was worse than when I started.

I had to drill in at angles and, whilst I kind of salvaged it, I wasn't happy.

So, yes, I have poor form!

...and am now asking how it should be done!

Its an M8 (or rather a couple of them) that are sheered in a 30yr old manifold. One came out fine the others the heads came off.

What is like to know is -

What size drill hole should I be attempting to make in an M8 in the hope of extracting the part?

Is the drill hole itself supposed to alleviate the pressure? If not, what breaks the rusty bond?

I'll have to drill by hand, so squaring and centering the hole with precision seems impossible.

Id really like to avoid just destroying the thread and having to helicoil.


Basically, is there a "proper" way to do this? Or does everyone just muddle through and hope for the best?

Thank you

 

[zzr1200]

A picture of the bolt and the manifold area would help no end.

I normally weld a wash/nut on the stud/bolt then heat the manifold as hot as possible, then try working it back n forth until it come out.

I have in the past welded on the washer/nut combo, then welded another bolt on the top, if possible heat the manifold to cherry red and use an air line blowgun to cool the stud while trying to loosen the stud.

Doubleboost has a couple of videos on Y/Tube about this...

 

[julianf]

I'll get a photo tomorrow, but they're the bolts that hold the clamps in place, that then, in turn, hold the turbo cartridge into the waste gate housing.

Maybe "manifold" was a misleading term.

They have sheered flush with the surface of the cast.

 

[julianf]

Here you go -

That was pre them loosing their heads. I cut the cartridge to get better access and it still went wrong!

I'm talking about the ones on the left, holding on the kidney shaped plates.

 

[zzr1200]

Arc/mig/or tig in the tool kit???

Gas axe...available??.....

Probably about the worst possible situation/plus shape to hold.

Are they blind bolt holes or do they go through into the snails shell?????

Certainly a repeated good dose of heat and some engine or ep90 type oil to start with would be my starting point on that....

PS :- What vehicle/plant?

 

[not done it yet]

My goto, these days is my set of left handed drills.
Start small (could be right handed drills initially).
Then go larger and larger with the lefties.
Usually the bolt will unscrew before or just as the core diameter is approached.

 

[Bullet2012]

boil balls in oil , then put sausage in toaster.

 

[Morris]

Another vote for left handed drills. They work surprisingly well. One company I worked at bought us all full sets for that very reason.

 

[knighty]

if you can drill close enough to the centre and keep stepping up in size, once there's not much of the old bolt left it takes the stress out of it and it'll normally come out, as above left handed drill bits work surprisingly well, either way drill on slow, running slow and push hard

how's the back of the hole? any sticking through?

my normal go to is to weld something too it, especially when it's out on the bench like that so you can weld down flat, clean it up best you can, lay a nut ontop of it and weld them together... fill the nut right up with weld, give it a sec to cool (so it's hot but not soft) and try turning it.... chances are it'll snap off... grab the next nut and repeat

handy to have a dozen nuts sitting ready

 

[Kram]

Send to @doubleboost for a proper repair.

. I cut the cartridge to get better access and it still went wrong!

Do you have a spare then, as thats the expensive bit you have turned to scrap!

Centre punch, pilot drill 3mm, if its off centre correct it with a carbide burr. Drill size as close to the tapping drill size of 6.8mm, then you'll just have a coil of thread to pick out.

2 flute twist drills do not like going up in small steps so its best to do it in one. If you want to use a smaller drill ~6mm then a 3-4mm burr can nibble it out to the thread.

 

[8ob]

@julianf I have checked in the manifoldery and there is a spare here if you need it, two studs to remove which won’t take ten minutes. If you make a mess of yours you can have this one.

Bob

 

[zzr1200]

@julianf I have checked in the manifoldery and there is a spare here if you need it, two studs to remove which won’t take ten minutes. If you make a mess of yours you can have this one.

Bob

View attachment 486706View attachment 486707

What vehicle/plant does it fit???

 

[Agroshield]

Looking at 8ob's picture, the holes are on a regular grid, perhaps even a pitch circle. That means you can make a drill jig* and secure it using the two unbroken ones. Then there is no excuse for the repair holes not to be central.

Make the holes in the jig larger than a helicoil tap and then bush them down to suit whatever smaller size you will use (initial pilot drill, standard tapping drill, standard tap, helicoil tapping drill, helicoil tap). You will need one of each drilling/tapping bush and two of the standard bolt size to secure it. Hang the jig and bushes up in the garage and hire it to the next person who asks.

Further food for this thread: https://www.mig-welding.co.uk/forum/threads/how-useful-are-metal-lathes.142325/

* possibly with a central hole and a T-bar that hooks into the hole so it would work for someone who is unfortunate enough to snap all four bolts.

 

[sako243]

What vehicle/plant does it fit???

Looks suspiciously like a 300Tdi

 

[Smallfry]

300 Tdi ?

I always end up snapping easyouts, thus making the situation worse, so dont use them any more.

On any other manufacturer, bolts and studs into a turbo are usually a hard stainless steel, so you will be wanting a cobalt drill. If you cant centre punch it, start off small and try to cajole the hole to the centre as best you can. Drill progressively bigger to 6.5mm. You will probably have to carefully tap the rest out.

The next time I do any turbo work like this, I am going to remove it complete with manifold, and hit the bolt heads with the MIG. Hopefully this will help free them up.

 

[8ob]

300 Tdi ?

I always end up snapping easyouts, thus making the situation worse, so dont use them any more.

On any other manufacturer, bolts and studs into a turbo are usually a hard stainless steel, so you will be wanting a cobalt drill. If you cant centre punch it, start off small and try to cajole the hole to the centre as best you can. Drill progressively bigger to 6.5mm. You will probably have to carefully tap the rest out.

The next time I do any turbo work like this, I am going to remove it complete with manifold, and hit the bolt heads with the MIG. Hopefully this will help free them up.

Yes TDI, those bolts are pretty hard, if the welded washer/nut routine doesn’t budge them second choice would be spark erosion.

Bob

 

[julianf]

The part is a 300 tdi manifold.

From the mix of suggestions above, it seems there is no "text book" way of dealing with it.

Im in no rush, so, i think my plan may be to leave them in a clip top drum of methylesters (penetrating fluid) for a month or so, and then have another look.

@8ob - thank you for the offer - i actually have 2-off these with the cartridges cut, and one that is still on an engine, with a stuffed cartridge, so i can afford to screw up before screwing up yours too!

I only really want one good one at the end of it all.

 

[Seadog]

my plan may be to leave them in a clip top drum of methylesters (penetrating fluid)

Acetone and ATF, 50/50.