One radiator not heating up

[terryplumb]

If there is no flow through the rad ,the other valve won't get hot.
It would be worth disconnecting the rad ,and opening each valve in turn to see if water flows freely from them both.

 

[Dereekoo]

If there is no flow through the rad ,the other valve won't get hot.
It would be worth disconnecting the rad ,and opening each valve in turn to see if water flows freely from them both.

All that suggested in #4 Terry, OP talks to much and no action

 

[old duffer]

Thanks. I tried this technique on Sunday. Shut all the rads except this. Yet it never budged beyond 40 degrees ( I have an infrared thermometer to check the temperature). When I slowly opened the other rads, they quickly jumped to 60 degrees within 10 minutes or so.

so it does have flow so you have eliminated the debris and valves. So now you are considering the volume flowing through so first you need to determine the pressure at inlet and outlet. A cheap pressure guage and a few push fir bits will enable you to do this.

 

[old duffer]

From the bare steel inside all the radiators, especially so, if the system has spent time with no inhibitor for a time - as is obvious from the OP's mentioned of dark, rusty water.

WTF is bare steel....you do say some crazy things

 

[Harry Bloomfield]

WTF is bare steel....you do say some crazy things

What do you think might the inner surface of a pressed steel radiator be made from? The clue is it begins with an S.

The S absorbs the O, of H2O, leaving the H as a gas, collecting in the system.

 

[old duffer]

What do you think might the inner surface of a pressed steel radiator be made from? The clue is it begins with an S.

The S absorbs the O, of H2O, leaving the H as a gas, collecting in the system.

hydrogen gas collects in the system....LOL....how many quarks are in their? what happens when the cosmic rays travel through the radiator? Answers on a phd thesis please

 

[Harry Bloomfield]

hydrogen gas collects in the system....LOL....how many quarks are in their? what happens when the cosmic rays travel through the radiator? Answers on a phd thesis please

What are you on today, have you sought help with your issues?

Hydrogen given off, is the result of the oxygen combining with the steel to form rust. A standard test, is to try igniting the gas which escapes from a radiator when you bleed it. The formula for rust is Fe2O3·nH2O which leaves a surplus of H2 - hydrogen..