Do you have a steel expansion tank up on the ceiling? Or a bladder tank?naga viper wrote:Bottom sounds hollow top not so much. Guessing water logged?
If it is a bladder tank, the bladder may have failed. depress the Schrader valve on the bottom of the tank and see if you get water. if you do, the tank is bad. if you get air, it may need the air pressure adjusted. Drain water from the boiler until the pressure reads zero, and adjust the air pressure in the tank to 12 psi.[/quote]
Steel expansion tank on ceiling (came with boiler) depressed valve only air came out.[/quote]
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Your horizontal steel expansion tank does not have an airtrol valve in the bottom of the tank that is fed from top tapping???????????
With the Airtrol valve you need a small wrench to bleed the water out to get the right 1/3 air 2/3 water ratio.
You have to have a 1/3 air 2/3 water ratio in a steel expansion tank that is hung in a ceiling joist.
The last but not least item is your Domestic Hot Water Coil may have a leak and is pressurising the steam chest with the homes feed water pressure.
Do you have a separate hot water heater??
To test the coil you need a complete Shraeder valve and 1/2"reducer bushing and a second 1/2" pipe plug that you can use to plug the domestic coils tappings to see if it is still good by pressurizing the DHW coil with air.