Minor Piston Leak 146

[macball]

I purchased a used 146 (likely late 70s vintage; I previously posted a thread regarding the split ebonite feed on this pen). The previous owner complained had leaked during a flight. Although the ink chamber was empty the pen had not been rinsed and there was quite a bit of dried ink in the chamber and feed. I noticed when flushing the piston that it didn't fill completely as if it were drawing air from somewhere. I removed the piston and found a lot of dried ink behind the piston, completely covering the plastic parts and brass. I cleaned that up, lubed the piston with Trident silicon grease and reassembled. I noticed that the pen did not completely fill with ink on the first draw. I used the pen a lot over the weekend and did not have any ink leakage on the outside of the pen. After using a full chamber of ink I tried refilling it and had the same difficulty getting a complete filling. I disassembled the piston mechanism again and discovered a small quantity of ink on the brass and plastic parts behind the piston. The piston is clearly not making a complete seal. I ran my fingers around the edge and noticed that it was not smooth. I don't think that this piston has ever been serviced so I don't know what could have caused the abrasions.

 

1. Could dried ink inside the ink chamber and repeated flushing the pen with water by moving the piston back and forth over a quantity of dried ink score the piston elastomer?

 

2. Can this be repaired by polishing with a high grit (8000 or 12000) micromesh to remove the rough edges that are preventing a good seal or will this reduce the diameter of the elastomer seal?

 

3. If the elastomer diameter is reduced can the elastomer be stretched to make a better seal with the barrel of the ink chamber? (I know that heat shrinks elastomer and cold expands it, but I would like to use this pen in places other than outside in a Canadian january and february!)

 

 

[meiers]

These are really interesting questions. I thank you for raising them and hope that experienced pen mechanics will respond. I am definitely following this thread.

 

I can only offer tentative guesses which I will keep to myself for the time being.

Edited June 2, 2015 by meiers

[Maxpens]

After reading this I would say a new piston is the best solution. You can also try with a little heat ( around 80 degrees ) to make the piston a little wider. That works from time to time but not for a long time. I would not recommend #2, I tried this but did not work proper, The material of the piston is PE, not good to grind.

 

kind regards

 

Max

[meiers]

I was going to say MB service.

[macball]

The problem with getting MB to do the service is that this is a pen with the monotone nib, split ebonite feed, and clear ink window (70's). I am afraid that if I send it to MB for service all I will get back is the original nib and the cap.

[niksch]

I got you covered.

[meiers]

The problem with getting MB to do the service is that this is a pen with the monotone nib, split ebonite feed, and clear ink window (70's). I am afraid that if I send it to MB for service all I will get back is the original nib and the cap.

I'd talk to Mr. Niksch.

[torstar]

Send it to HQ or find a master on here who will help you.

 

It was only a 146 to me, so back it went for full service.

[macball]

Thanks for all the input. The advice seems to be to send it to MB for service and risk replacement of vintage parts or get a replacement piston. From my perspective I thought it wouldn't make a difference if I tried to repair and it didn't work because it would need to be replaced anyway.

 

It is hard to describe the damage to the piston without photographs and it is hard to photograph. The area of concern was about a 10 degree segment around the circumference. It consisted of a roughness that was easier to feel than see. I speculate that the pen sat in a drawer and the ink chamber dried out. To fill the pen or flush it the piston, which may have been stuck, was moved back and forth across the crystallized ink that scored the plastic. I said that it was elastomer but I think elastomers are rubber or silicon. As pointed out by another poster, it seems to be made of clear polyethylene while the black post seems to be made of harder polypropylene. It was pointed out that polyethylene is hard to grind, but I wanted to polish the plastic rather than grind it. An 8000 and 12000 micro mesh will do more polishing than grinding. Any polishing involves the removal of material so it is matter of subtle polishing. I went slow rather than aggressive. The polishing removed the roughness although there are striations remaining. I reassembled the piston and I could not detect a difference in the fit. I was able to get a full chamber of ink with two draws of the piston whereas before I could not get a full charge of ink with several piston cycles. I will go though a couple of ink charges to see if the fix is permanent and I will disassemble the piston again to see if there is any evidence of ink or moisture behind the piston. If there continues to be a problem I will try to get a replacement part. In the meantime the polishing seems to have worked. I will report back in a couple of weeks.

[meiers]

Wonderful. Please tell us how it works out for you. I am following this thread with interest.

[macball]

As promised, I am pleased to report back on the longer term effectiveness of the piston repair.

 

As posted by many on this forum, storing a pen with ink in the barrel whether deliberately or by accident can cause serious problems. The piston seal may stick to the barrel. If that happens there is no way to flush the pen with water to re-dissolve the dry ink. Turning the filler knob with a stuck piston can cause shear forces on the oval diameter piston guide spindle causing it to deform or even break. Even if the piston moves, pulling the seal back and forth across lumps of crystallized dried ink during the process of flushing can wear the seal causing it to leak air and ink. A defective seal will prevent the pen from filling completely and whatever ink is in the barrel will leak behind the seal and eventually out the top of the pen around the filler knob. The latter is what happened to me.

 

As described above, the pen appeared to have a defective seal for a long time. The previous owner complained of a leaking pen and the plastic and brass behind the piston were caked with dried ink. The piston had a rough area that was leaking air and ink. I polished the roughness using micro mesh to eliminate the roughness without reducing the diameter of the piston seal significantly.

 

After a couple of weeks and several loads of ink I examined the pen for evidence of leakage behind the piston. After emptying I noticed what appeared to be ink behind the piston through the reservoir window. This was an illusion because the piston seal is semitransparent and shaped like a toilet plunger. Dark ink inside the indentation where it is attached to the spindle may appear as if it is behind the piston because the indentation is behind the point of contact with the barrel.

 

After removing the piston assembly the plastic and brass behind the piston was dry

 

I would conclude that if the abrasions of the piston seal that cause leakage of air and ink are minor they can be polished with micro mesh to reestablish a seal with the barrel. As with most pen repairs, go slow and only polish enough to produce a seal because over polishing or sanding will change the shape of the piston seal. Attempting a repair is worth a try because a leaking piston will require replacement anyway.