Whats wrong with the LeeCo valve?

In our application, it does not seal after it is cracked and 100 psi is the maximum they can make in the .187 size.

As far as I recall they have a wide gap between the cracking pressure the re-sealing pressure (~20%). This means that they may crack at 100 psi but will re-seal only when the pressure reduces to 70-80 psi. I am not familiar with other company that makes miniature products such as Lee Co. Is it for liquid or gas?

I had the chance to develop a gas pressure relief valve for 1100 psi with less than 5% gap between the cracking and re-sealing pressures but it had larger diameter.

http://www.webspawner.com/users/israelkk/

We are using it in oil, and it doesn't reseal at any pressure or amount of time.  We pull a vacum against the seal in the oil filling process and the valve leaks in this situation.

try www.highpressure.com

Look at a Crosby 900 series. If memory serves it is available with an elastomeric seat insert.  Farris would be a comparable vendor, but I do not know their model for the competitive valve.  

Swagelok and Parker both sell valves in the rage that you're looking for.

Could you point me at a model from Swagelok or Parker?  They all seem to be much larger than the Lee Co. valve.  I don't think I made it very clear in the first post, but this is a .187" diameter by .500" long, so its very small compared to standard relief valves.

Can you post the Lee catalog number?
Can you provide more information on the circuit arrangement it was not clear form your previous post. Especially the following statement: "We pull a vacuum against the seal in the oil filling process and the valve leaks in this situation"
What kind of oil?

Yeah, .5 is pretty small.  The .187 requirement is OK, however.  You might try to give them a call and see what they recommend.

Sure, here is the link to them http://www.theleeco.com/VALVWEB2.NSF/1c4342c9ada019ae852567de00763051/60fe81e782f888a385256842007b9b32?OpenDocument

I'll try to clear up how its used in this application.  We have a volume that has only one input to be filled and a fairly complex shape and this Lee Co. valve inserted to allow the volume to vent if the pressure exceeds XXXpsi once the system is filled and closed.  But since there is only one input, you can't just pour in the oil, you have to pull a vacuum on the volume with a container of oil inline and let the oil backfill into the void.  It works very well until this valve doesn't seal after it has vented once.

Eltron:  We've worked with them in the past to work with this, and they can do it in a .281 size but can't exceed 100psi in the .187 size.  Which is why I'm trying to find a different vendor who might have something that works already.

If you could scale up just a skosh you could use a lubrication type relief valve.  The SAE fitting is to show the construction and the Alemite reference catalogue has a valve that will meet you pressure needs.  
All fitting manufactures have this type relief valve or some even have vent valves that have high cracking pressures.

http://www.saeproducts.com/relief.html

http://www.ajfittings.com/data%20sheets/Alemite%20Catalog%202005/Alemite_Product_Catalog.pdf