Seiko 6139: Unable to remove winding stem because of corrosion

[stm]

I'm trying to disassemble a Seiko 6139 chronograph. I got it as non-running from Ebay. When I opened it, it became clear that there is some rust in the movement.

The main problem currently is that I cannot remove the winding stem and crown. As far as I understand it should be possible to unlock the stem by pushing into the hole that I marked with a red circle in this phote:

It looks like the button to release the winding stem is corroded. It is hard to see what is inside the hole.

What are my options if the winding stem release mechanism itself is broken? Would I need to saw somehow through the winding stem to get the movement out of the case?

Thanks

Stephan

[AndyGSi]

Yes that's the correct hole for the stem release.

You could try some penetrating oil in the hole and see if that frees it up.

Failing that what's the front like? Can you remove the bezel/crystal and access the dial?

[Nucejoe]

 Penetrating oil might do, but be careful not to put to much oil anywhere when you will have the watch face down for hours.  If no joy, you ought to remove parts till you get to the stem. In which case; 

1-Identify exact caliber version of the movement, there is 6139A & 6139B ,,,, or take plenty of pictures as you disassemble. 

2-Google for  disassembly images of your movement.

3-You best loosen a bit ,screws to chrono module, to get enough space to discharge mainspring power through the click.

4-With all power discharged, remove the balance-bridge assembly.

5-Remove all parts you see to get to the stem. 

There you should see the rust or whatever mess is present, scrape off as much rust as you can, then apply penetrating oil.

Pictures saves you time with reassembly, as chrono complications are usually confusing.

I often forget how Chrono pieces engage to work.

Good luck Pal

[stm]

1 hour ago, AndyGSi said:

Yes that's the correct hole for the stem release.

You could try some penetrating oil in the hole and see if that frees it up.

Failing that what's the front like? Can you remove the bezel/crystal and access the dial?

I had already tried to apply WD40 and let it rest for a few days, but without success.

This is the watch from the fron:

I doubt that I can remove the mineral glass from the front. Even if, how would I get beyond the dial then?

44 minutes ago, Nucejoe said:

 Penetrating oil might do, but be careful not to put to much oil anywhere when you will have the watch face down for hours.  If no joy, you ought to remove parts till you get to the stem. In which case; 

1-Identify exact caliber version of the movement, there is 6139A & 6139B ,,,, or take plenty of pictures as you disassemble. 

2-Google for  disassembly images of your movement.

3-You best loosen a bit ,screws to chrono module, to get enough space to discharge mainspring power through the click.

4-With all power discharged, remove the balance-bridge assembly.

5-Remove all parts you see to get to the stem. 

There you should see the rust or whatever mess is present, scrape off as much rust as you can, then apply penetrating oil.

Pictures saves you time with reassembly, as chrono complications are usually confusing.

I often forget how Chrono pieces engage to work.

Good luck Pal

Thanks for the advice. As written before, I had already tried to apply WD40 oil but without success. I will then try to disassemble the movement while it is in the case and try to get to the stem.

[AndyGSi]

4 minutes ago, stm said:

I doubt that I can remove the mineral glass from the front. Even if, how would I get beyond the dial then?

I'd forgotten these dials are held in with dial screws so as you say that's a no.

As @Nucejoe said the only way forward is to start disassembly but make sure you let the power down before going too far.

[rjenkinsgb]

12 minutes ago, stm said:

I had already tried to apply WD40 and let it rest for a few days, but without success.

Normal WD40 is not a good penetrating oil; it's solvent based and thickens as that evaporates.

(There is a WD40 branded penetrating oil, but that is very different to the original stuff).

You need something to break down the rust. Evaporust or EDTA solution should do that - if you can remove enough WD40 residue with a solvent for it to get to the actual metal surface.

Try and work with the watch on edge & angled towards the back, so any excess liquids run out rather than getting to the dial.

dd small drops of whichever liquid to the setting lever hole at regular intervals until the rust has visibly reduced?

(The EDTA based rust remover is five grams of EDTA powder per 100ml deionised water, then a trace of citric acid to bring it nearer neutral ph, and a few drops of washing up liquid/dish soap to help it get through any traces of oil. It works extremely well, with next to no effect on good metal).

 

[stm]

I was now able to remove the parts layer over the winding stem. The corrosion looks pretty massive:

I then applied a citric acid solution multiple times to the winding stem and its surroundings, and I was able to remove some of the rust:

Nevertheless the window stem still does not move and cannot be removed.

[AndyGSi]

Looks like the only way is to remove the bezel and access the keyless works from the dial side.

[RichardHarris123]

Diamond cutting wire could be passed under the stem and the stem cut from behind. 

[Nucejoe]

 Try removing  bezel and the winding crown. See if you can slide out the movement with stem attached, plus remvoning the case tube helps. 

 Otherwise I just cut the stem, remove dial and hands ,dismantle as many parts I can , soak in Coca Cola , which doesn't hurt metals, but softens what you see as rust. 

Regs

[stm]

22 hours ago, AndyGSi said:

Looks like the only way is to remove the bezel and access the keyless works from the dial side.

I looked at several videos about disassembling Seiko 6139s, and from that it is not clear to me how I could remove the dial from the front.

21 hours ago, RichardHarris123 said:

Diamond cutting wire could be passed under the stem and the stem cut from behind. 

 

21 hours ago, Nucejoe said:

 Try removing  bezel and the winding crown. See if you can slide out the movement with stem attached, plus remvoning the case tube helps. 

 Otherwise I just cut the stem, remove dial and hands ,dismantle as many parts I can , soak in Coca Cola , which doesn't hurt metals, but softens what you see as rust. 

Regs

That's what I thought earlier, that I will have to cut the stem then. What is visible from the stem inside the movement looks so corroded that it will have to be replaced anyway.

Thanks for all the advice! I will report my progress after I have acquired a cutting wire and after cutting the stem.

[RichardHarris123]

Let us know how you get on. 

[AndyGSi]

9 minutes ago, stm said:

I looked at several videos about disassembling Seiko 6139s, and from that it is not clear to me how I could remove the dial from the front.

It all depends on the case as sometimes you can rotate the movement 90 degrees to gain access to the screw.

[stm]

14 minutes ago, AndyGSi said:

It all depends on the case as sometimes you can rotate the movement 90 degrees to gain access to the screw.

You mean rotate 90 degrees around the stem? Ok, that makes sense.

26 minutes ago, stm said:

Otherwise I just cut the stem, remove dial and hands ,dismantle as many parts I can , soak in Coca Cola

Regarding the Coca Cola, is this a better option than a citric acid solution?

[Nucejoe]

8 minutes ago, stm said:

That's what I thought earlier, that I will have to cut the stem then. What is visible from the stem inside the movement looks so corroded that it will have to be replaced anyway.

If you did cut the stem, there still some stem sticking out of the winding crown, thats how you want the crown.

Next remove balance+ cock assembly + fork, and throw the rest of the movement + the crown in Coca Cola for a 30 hrs soak. Coca Cola dissolves oil & grease. ( much better than WD40 oil )

Then start to disassemble before Coke dries out.  

If dial plate doesn't come out from back of the case, then it must have  been loaded from the front, so bezel must be removed. 

Good luck

 

 

4 minutes ago, stm said:

Regarding the Coca Cola, is this a better option than a citric acid solution?

Coca cola doesn't damage base metals, penetrate better than any oil base solution, dissolves oil/ grease.

WD40 is water base and breaks rust bonds, not oil.

Try coca cola , you be surprised how well it works.

 

[stm]

On 4/10/2025 at 9:37 PM, Nucejoe said:

Try coca cola , you be surprised how well it works.

Ok, I tried it and it worked!

I performed the following steps:

• sawed through stem with diamond cutting wire, then I was able to remove the movement from the case
• disassembled the hands and the dial
• dipped the movement for 24h in Coca Cola
• rinsed in isopropyl alcohol
• ultrasonic cleaner with watch cleaning solution and then with distilled water
• dipped in benzine
• provisional drying

After that I was able to disassemble almost everything from the movement, except the winding stem and two part of the keyless works.

Some pictures from the process:

Ready for sawing through the stem:

After sawing the stem the movement was removed from the case:

Removed the dial. What came out looked pretty horrifying to me  The week day disk was crumbling and is totally destroyed:

The dial front and back:

The only parts remaining in the ground plate are for the moment the winding stem with gears and two parts of the keyless works:

The winding stem does still cannot be removed. I will probably have to saw through the remaing part as well.

Edited Monday at 06:42 PM by stm
Clarified remaining parts after disassembly

[AndyGSi]

I'm surprised how well the dial looks.

How is the rest of the movement?

[stm]

2 hours ago, AndyGSi said:

I'm surprised how well the dial looks.

Really? I had hoped it would come out in better shape from behind the heavily scratched crystal.

2 hours ago, AndyGSi said:

How is the rest of the movement?

The balance and the pallet fork look good. Some parts look heavily corroded, but I will dip them in Coca Cola as well to get the rust off.

One part is definitely broken, the "pawl lever with jewel" (part number 831611):

And I forgot to mention that one screw was stuck so firmly that I broke it in half when I tried to unscrew it (marked with red):

Edited Monday at 09:15 PM by stm
Fixed typo

[AndyGSi]

At least you shouldn't have any problems getting replacement parts.