Gas water heater pilot goes out after heating

[EDM]

Recently our gas water heater pilot has been going out after the burner has heated
the water. The interesting thing is that it does not seem to be possible to relight the
pilot for a while afterward, when depressing the button to light it in the PILOT position,
it will light but goes out slowly as the button is released. However, later, it will light
and stay on.

Have replaced the thermocouple but that does not seem to have made a difference.
Will try cleaning the pilot orifice, but am I correct in assuming it is probably the gas valve?

The pilot flame is fairly large but I do hear a sputtering noise.
I do not think based on observation that there is low gas pressure in the house.

Thanks.

 

[Jadnashua]

Is the thermocouple properly positioned in the pilot flame?

 

[Sponsor]

 

[EDM]

I believe so. It certainly was for 15 years before it started acting up.
After replacing the thermocouple the pilot will stay on after being initially lit.
It is only after the burner has been on heating the tank that it goes out
and, for a while, after relighting won't stay lit. Then it will work OK.

I think the new thermocouple is in the correct position in the pilot flame,
about 1/4" to 1/2" of the end is in it.

 

[Plumber69]

Is there a high limit reset on the tank?. It could be a manual red button or one that resets it self.

 

[EDM]

I looked, but I don't see any kind of reset. The valve is a RobertShaw R110RTSP 66-178-335.

Was able to test the old thermocouple held in the flame of the gas stove, it read 35mV.

 

[Plumber69]

I looked, but I don't see any kind of reset. The valve is a RobertShaw R110RTSP 66-178-335.

Was able to test the old thermocouple held in the flame of the gas stove, it read 35mV.

might look like this. Its not on the gas valve. below it

 

[EDM]

Is there a high limit reset on the tank?. It could be a manual red button or one that resets it self.

No, there does not appear to be any kind of limit reset.

It does seem like the pilot will only stay lit after enough time has passed since the
main burner has been on (or, maybe, after the tank has cooled down). It does not
reach the same hot water temperature that it used to despite being on the highest
temperature setting when it is heating.

 

[Plumber69]

Ive had gas tanks that would only leak inside when heated up. Then would drip and put the pilot out

 

[EDM]

Replacing the gas valve/thermostat fixed the problem. I suspect that the solenoid
was faulty, and would stay open for a while, but not continuously even though the
thermocouple voltage was OK.

Appreciate all of the advice/suggestions. Will end up replacing the tank eventually
given the age but needed to get it back operational. Checked carefully - no leaks.