Two stoves I'm fettling today both had leaky NRVs so I removed, cleaned made and fitted new pips (using the cup itself as a trepan). I also made and fitted new lead washers. One stove worked as it should while the other still leaked through the pump. So, to ascertain whether it was stove or NRV at fault I swapped them over. It's one of the NRVs I've stripped it again and can see nothing wrong: the spring is in good condition and long enough, there is no damage to the NRV and the lead washer has seated itself nicely. So what else can it be? It's not a slow leak either but strong enough to push the pump rod out quickly. The only comment I can think to make is the pip is slightly recessed as the nitrile sheet I have is too thin - but it's never been a problem with others I've re-pipped. I've had to call it time for today but tomorrow I may mix and match parts from both NRVs to see if I can isolate it. Failing that I may try to make a thicker pip by super-gluing some nitrile together. Cheers, John
John, your leak could be the soldering at the bottom of the pump tube. No way to get at this without removing the tube sadly, so try every thing else first.
Doen't his NRV mix and match test rule that out? I have sometimes had to cut a few pips before I got one that worked as it should. Also, could an uneven mating bit (what ever the hole contacted by the pip is called) be the problem?
Thanks for the suggestions, chaps, all appreciated. A leaky soldered joint in the tube was my first thought but by swapping the NRVs over I eliminated the possibility. I'll make another pip and see. I always clean the mating surface by gently rubbing it on some fine wet & dry. Cheers, John
For nrv pips ive had very good luck just using a simple rotary type leather hole punch and setting it to slightly larger than the nrv carrier, as the punch does tend to hourglass the rubber a bit on the ends. Have had every one ive punched work no problem though. Thickness of the material does seem to be a big factor though for nrv's i ussually go with 3mm I've found that less doesnt give enough pressure
Hi, if you look at topic 15033, its a tube removal i had to do on a meva, i had to replace the end cap of the tube to fit a new nrv thread, but when i soldered the end cap on and then soldered the tube back in, it behaved the same as yours is by pushing the pump rod back out. After much messing about with nrvs which didnt help it dawned on my that the end cap may not have sealed enough with the solder. So i bit the bullet and removed the tube and resoldered the end cap and re fitted the tube back in and problem solved, no more pump rod coming back out. Maybe by removing a stuck nrv to forcefully or to many times this may fracture the end cap solder??? hope this helps, and how did you make a lead washer for the nrv?? Colin
Hi Colin, Thanks for the suggestion but I'd eliminated the thought of leaky solder by swapping the NRV into a known good stove where it was fine but the suspect NRV then leaked in the good stove. Tomorrow I'll make some more pips, possibly doubling the thickness and, if that doesn't work,swap NRV components around. I make my lead washer out of code 4 flashing lead. I make a hole big enough for theNRV to just fit through, 'screw' the NRV thread in to it and then cut off the surplus around the body of the NRV. Lead is so soft it moulds itself into a good seal. Well, usually anyway Cheers, John
Hi John I have had trouble setting new pips too, i drilled the pip seating into 3mm rubber and found it compressed it in, then when i fitted it back in the nrv the rubber swelled up and poured over the edges which then stuck to the sides and caused it to push the pump rod out again, tricky little things But i cut the extra rubber of the end of the pip and that solved it Havent found a steel pen inner yet to try. Colin
