I have a crusty old Phoebus 625 that I replaced all the seals on, but it still leaks past the NRV when under pressure. With the screw-down plunger I didn’t notice this right away as the stove ran perfectly. But when I pulled the plunger out it had filled with naphtha after only 8 minutes of running. The NRV pip is brand new from the Fettlebox. The original pip I replaced was a cork one. What should I consider doing next? Thanks!
Was the new pip punched out straight, many come crooked, I usually buy extra so I can sort thru them. Sometimes changing them around works. It can be interesting sorting out why a NRV still leaks, so many factors. Duane
@fimbulvetr first of all great stove the 625 i have one and love it and all ways wanted one, a great point from @hikerduane i would first change the pip to another one, another point is the spring still in good condition, looking at it from the photo it looks good, i have failed NRVs on stoves that have failed after changing the pip due to the lead washer and from a failed solder joint from the base which the NRV screws into,
This reminded me that the original repair kit that came with the stove had a spare unused cork pip. I switched in that one, boiled some water for tea, and that seems to have stopped the leak. Problem sorted, I guess. Here are a couple shots of the stove in action.
Hang the pump up, free and vertical. Fill the pump with fuel and see, where the leak is. Btw a cork pip lasts 100 years. It can be softened in hot water. Radler
Good on ya for getting it going. I too struggle sometimes with new pips. Turn em over, dink with them, sometimes let them "seat" for a few days.
I inadvertently let that one "seat" for a couple months. When I first changed it, it leaked so I drained the tank, set it aside as something to deal with later and forgot about it until this week. I still can't see anything wrong with the leaky pip after pulling it out. I'm just going to assume that stove prefers cork pips and keep an eye on it in case it leaks again.
Hello, for my experience: Cork is softer than Viton. Stoves that used cork originally, have “softer” springs that sometimes are unable to successfully push the harder Viton pips enough to make the seal. Replacing springs too is not straightforward, tests are required. So when fettling NRVs some luck and some tests are needed. Always better to pressurize and fill the pump tube with water to check for leaks before fueling the stoves, especially with gasoline. Nicola
@Nicola Francesco Elia The spring being too weak to provide sufficient force to get a seal with a harder pip is something I would never have thought of. Maybe the spring not being long enough with a different thickness of pip but the stiffness would definitely not have entertained my remaining brain cell. Regards John
It isn't the spring that provide the sealing pressure, it is the pressure inside the tank. If you put a stronger spring in they are nearly impossible to pump.
@Majicwrench Exact! And because the Phoebus Nº 625 has a very robust shut-off valve, this stove can hold pressure for many hours or days. The weak-spring-theory is nonsense here. Radler
@Majicwrench I am not talking about stronger springs, but adequate springs for the pip in use. For example (and just one example) old Hasag 10/11 have different NRVs than usual and springs are not interchangeable with Primus ones for example (because primus ones are longer and stronger). Ok that internal pressure participates in the sealing, but for logic the spring must be there for a reason… I am not writing the NRV bible here, just sharing my experience, nonsense or not. Cheers
Additionally, on the example above (and 625 should work just fine with any Viton pip) I can clearly see a pip not inserted correctly, so probably not facing perfectly flat against the NRV head and so failing to seal (cork in these cases is more forgiving):
That picture was after I had fiddled with it for a quite while and given up on that pip in frustration. I had that NRV apart many times trying to get it to seal. The cork one works great though.
I put a cork pip in one of my stoves, just because that is what was in there. Can't recall which stove.
The Phoebus Nº 625 is one of the best stoves ever made. It has been constructed for expedition or military conditions. All the most crucial parts are located in the pump: filler gasket, NRV (non return valve), pump leather. I remember a seller in Switzerland, who sold this stove also in a "expedition version" with a spare pump. This was in the fifties or sixties. The advantage of the easy removable pump is obvious under field conditions. The most common problems can be solved without any tools, just by replacing the pump. In our case here, it seems the owner tried to do something good by blindly replacing the cork pip in the NRV. Picture 1 shows the opened NRV with case, spring and pip. The head of the NRV is still mounted in the pump bottom. The correct way would be, first to dismount the whole NRV with a NRV-key. When you try opening the NRV in situ, you risk the following: You involuntarily turn the NRV-head into the pump-bottom. When you later remount the NRV-case and tighten, you unloose the NRV-head from the pump-bottom, again involuntarily. And a new mysterious leak is created. Radler
@fimbulvetr Yes, you are on the path. There are always three possibilities for leaks: the pip, slack NRV and the thin lead gasket under the NRV-head. Radler
