[phico3]

I have a very old gas furnace was build on 1965,it still works very good, but I found out there is a little problem :when the gas valve opens,there has a little explosion before the furnace lit up;there is a small tube came out from gas valve and go to near pilot light (small fire old style not electronics type), the pilot sensor is a metal build on ceramic with 2 screws wire connection series with gas valve (in case no pilot to shut off gas valve), what I guess the tube is to make the smooth the starting of lit up the main fire(furnace on),when the gas valve opens, a little gas flow through the tube go to the lit pilot before too much gas spread around and makes as a big pilot that's smooth the heat goes on( big gas lit up) ,also it service as the pilot if the regular pilot extinguished during heat was on, I found the tube has no gas came out if my guess the tube was for,anybody can tell me what the tube for ?Am I right? Thanks. George

[hvac1000]

I believe the tube you are referring to is the old style safety bleed tube. It allows a pressure balance without venting the gas into the air because they burn it off in the combustion chamber.

[phico3]

Thank you for your answer.Another question :is there suppose has certain level of oil in the gas valve chamber ? (when open the top cover of the gas valve:half of the relay dipped inside the likes oil well)

[hvac1000]

You are not supposed to open the gas valve. There are no used serviceable parts inside. Call for service before you hurt yourself and other.