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This is the third time that I've had a leaking Presta valve on the tube. There must be a way of repairing the Presta valve rather than having to discard a good tube. Someone did it by applying glue, but I didn't watch closely enough to see where he put the glue. What can I do?

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Please clarify something for me. Are you getting leaks from the top of the valve itself or from the base, where the stem meets the rubber tube? –  DC_CARR Dec 16 '10 at 20:06
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I think there must have been a worldwide change in the technology used recently, since all of a sudden I too have been having the values come off from the tube. I rarely get punctures now, 80% of my throwaways are because of values detaching - Vittoria & Specialized being the brands I have had trouble with –  Anthony K Dec 17 '10 at 4:36

2 Answers 2

First save the valve out of any tubes you discard (if the valve is good). And you can buy valve core separate.

The valve was two sets of thread. One to open and close the valve and the other to remove the valve core.

Removing the pump can loosen the valve core. You can use a tool such as core removal tool or a small pair of pliers to tighten the core. If it gets loose I use just a dab of locktite on the threads but you must be very careful to not get any on the gasket or the valve will stick. I have a bad set of tubes and did this to all of them up front. Just a dab on the threads in the middle. And open the valve before you tighten it. presta core

valve core video

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Not all presta valves have removable cores. Here's an image I found showing valves with and without removable cores. It's also not clear if the OP is having problems with the valves themselves, or where the valves attach to the tubes. The bit about using glue makes me think it's the latter. –  jimirings Jul 17 at 1:16
    
I'm not "hating you." I comment on many, many posts throughout the day. I am not the only one who has noted that the question is unclear. See the first comment on the question itself and the other answer. The glue sounds to me like someone attempting to reattach a valve that has separated from the tube. Glue should not be needed to replace a valve core. I note that not all cores are replaceable because you say to save any valve. This implies that they are all replaceable. –  jimirings Jul 17 at 1:42
    
@jimirings Truce hating is not the right word. I would hope that serviceable was implied. –  Blam Jul 17 at 1:44

You could try rubber cement however, you will probably still have a slow leak.

You best solution is to prevent the valve from separating from the tube. To do this, I don't put the retaining nut on until after I have fully inflated the tire. Once the tire is inflated, I screw the nut on just tight enough that it won't fall off. You could add some loc-tite but I don't and haven't had a problem. If you over tighten the nut, you are going to cause the valve to separate from the tube.

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Additionally applying a light coating of baby powder to the tube will prevent the tube from sticking to the tire. If the tube is sticking to the tire anytime the tire slips on the rim (like when you are applying the breaks hard) the tire will pull on the tube which in turn pulls on the valve. Which if it happens enough will put a whole in your tire near the bottom of the valve. –  Ben Dec 17 '10 at 22:54

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