Heat Exchanger broken screw

[djousset]

So this happened.....I've watched the You Tube vids on extractors, drilling out etc. Does anyone know what behind here and how deep you can drill in this location? (heat exchanger aft end screw on Yanmar 2gm20f)
Good news is the exchanger looked great so there's that

[Calif.Ted]

That may have been a stud, if that's the front side, that was 18 mm total length, see page 30 part #17 of the parts manual.
http://j30.us/files/Yanmar-2GM20-Parts-List.pdf

[pesarsten]

I have found that welding a nut to the exposed stud is an easy way to extract the broken stud.

Dont forget the PB blaster!

[Celestialsailor]

If it an aluminum exchanger, you'll know when you a through the stud. Although I would not use an extractor in this case. I am a Toolmaker/Machinist, so I've fixed these little problems many times.

a couple of questions...1) was it a stud with a nut or a machine screw that twisted off.
2) Is the exchanger aluminum.
3) If it was a machine screw that twisted off, id there room for a stud instead?

4) Is the exchanger off now?

[djousset]

@celestialsailor: not a stud, it's a hex nut head screw that sheared off. Not enough protruding to grab. I supposed I could put a stud once I get it off.
I don't believe the heat exchanger is aluminum, and no, it is not off.

[sailorboy1]

I had the same thing 2 years ago on my 4JH3 and bet it is the same. If so it threads all the way in.

In end I took my whole heat exchanger/exhaust manifold off and took it to a machine shop that got 1 out using the welded nut trick and drilled/tapped/helicoiled the other and it was like $120

[Celestialsailor]

Originally Posted by djousset

@celestialsailor: not a stud, it's a hex nut head screw that sheared off. Not enough protruding to grab. I supposed I could put a stud once I get it off.
I don't believe the heat exchanger is aluminum, and no, it is not off.

Originally Posted by sailorboy1

I had the same thing 2 years ago on my 4JH3 and bet it is the same. If so it threads all the way in.

In end I took my whole heat exchanger/exhaust manifold off and took it to a machine shop that got 1 out using the welded nut trick and drilled/tapped/helicoiled the other and it was like $120

Hi djousset...as sailorboy1 explains, this is the way to do it. If all else fails I can get it out for you and you would only have to pay postage. You can try rocking out what is left of the shank of the bolt. But if you do that please please please use heat from a propane torch. If you don't you'll just bugger up the shank.

[Scubaseas]

Originally Posted by djousset

So this happened.....I've watched the You Tube vids on extractors, drilling out etc. Does anyone know what behind here and how deep you can drill in this location? (heat exchanger aft end screw on Yanmar 2gm20f)
Good news is the exchanger looked great so there's that

You could drill in 20mm or so. Welding a nut would be my go to on this.

[Ninedotsix]

Another approach to try before the welded nut trick:
Heat the casting and screw, allow to cool, then using a small cold chisel and a small hammer, keep tapping the chisel and tangentially tease the screw to unscrew it from the tapped hole. You can also use a pin punch.
No heavy hitting, that won't be necessary as brute force is not the trick.
Light, repeated tapping from all angles on the tangent will rock it out.

Hold your mouth right and be patient.
You want to dig into the screw, but not shear it off.

Hints: Using a small- size tip in an oxy-acetylene torch, adjust to an oxidizing flame.
Heat the casting around the screw, keeping the flame moving.
Bring the casting temp up and also play heat on the end of the screw.
Allow to cool.
When warm to touch, put penetrating oil into the threads.

I have used this technique a number of times to remove screws from "priceless" castings on industrial machinery.

Best of Luck ~ P

[oleman]

Save yourself a lot of grief. Remove the exchanger and take it to a machine shop with a milling machine.

The worst possible situation is a steel bolt screwed into aluminum when it refuses to rotate.

A good machine shop with the milling machine should be able to find the center of the broken screw and neatly drill it out with the same angle as the existing hole. If they really know what they are doing, they will be able to remove it without damaging the surrounding material, but I expect they will just want to hog it out and replace with a heli-coil, which will eventually cause more problems.

[AKA-None]

If you heat the casting it will expand
If you take to long then so will the bolt
In the shipyard we would heat the casting then quickly before the bolt expanded attempt to remove the bolt key part is do not stop once it starts moving as the bolt will start to expand thus seizing
All else fails we would drill with left hand drill working up almost to the threads then use an ez out
Most people use to small of an ez out
The above is based on my experience but ymmv

[glenn.225]

Originally Posted by Ninedotsix

Another approach to try before the welded nut trick:
Heat the casting and screw, allow to cool, then using a small cold chisel and a small hammer, keep tapping the chisel and tangentially tease the screw to unscrew it from the tapped hole. You can also use a pin punch.
No heavy hitting, that won't be necessary as brute force is not the trick.
Light, repeated tapping from all angles on the tangent will rock it out.

Hold your mouth right and be patient.
You want to dig into the screw, but not shear it off.

Hints: Using a small- size tip in an oxy-acetylene torch, adjust to an oxidizing flame.
Heat the casting around the screw, keeping the flame moving.
Bring the casting temp up and also play heat on the end of the screw.
Allow to cool.
When warm to touch, put penetrating oil into the threads.

I have used this technique a number of times to remove screws from "priceless" castings on industrial machinery.

Best of Luck ~ P

1+ this is the way, if its not too badly rusted. Lots of patience, it will be out in an hour or two. I know not everyone has a ox-acetylene torch but a mapp gas kit is cheap and will work fine. Heat the casing not the bolt.

[glenn.225]

One of these are priceless when you need it. I've had mine for years and it's payed for itself over and over. The are used collars to center the drill bit.



https://www.ridgid.com/ca/en/25-screw-extractor-set#

[Searles]

The welded nut is the easiest answer especially if the manifold is still on the motor ,even if the thread is shot force a hex nut on the remains , a small arc welder will do the job insitu ,let cool and tap lightly on end with small hammer while using a little undo pressure .⛵️⚓️

[jamhass]

If you decide to remove the unit and take it to a machinist, consider finding a machine shop with an Electric Discharge Machine (EDM.) These are the go-to tool for removing dissimilar screws (such as stainless in aluminum.)

I once broke a stud in an aluminum Lotus engine block. The EDM took out the steel and left the aluminum completely untouched, even leaving the aluminum threads in perfect condition.

Good luck.