I have hot water base board heat. About a week ago, I noticed I couldn't get the house to go above 62 degrees. When I touch the baseboards the two rooms at the beginning of the loop are hot, but as I go farther through the house the units are colder and colder leaving the two bedrooms freezing cold. Last winter I had a problem with a pipe freezing, so now I keep a small heater on in the basement to avoid this happening again. The circulating pump comes on and is only a year old. As I said the problem started suddenly. What could be wrong? Can I fix it myself?

Air in the system? Bleed baseboard system.
Low boiler water pressure? Raise water pressure

These two items are the cause of the condition you are experiencing.

There can be others but not likely.

As well, check that the zone valve is open ( if you have one) and the pump is running ? To be noted, just because a pump is running does not mean it is moving water, because of system pressure or air as hvac1000 stated... you may have a frozen pipe section again...

I had the same problem and it was air in the line. There should be bleeders on each heater at one end. If the pump is on all the time just crack that little valve open and see if air comes out. When water starts to come shut off.

Follow-up question: One zone services three bedrooms and a bathroom. First bedroom, bathroom, and second bedroom heat well. Third bedroom at the end of the run is always cold. Its radiator is warm, but not hot. The system does not include valves to regulate water flow by room, only flappers over the pipe/diffusers.
Can there be air in the third bedroom's pipe when the other rooms are fine?
Thanks in advance for assisting!

Beginner at this and presumed the radiators were incorrectly sized causing the water to be cooled too much before reaching the third bedroom. I.E. the system is about twenty years old and it is possible/likely that room was always cold.

Three floors in house heat was in all floors than yesterday no heat on first floor heaters are located on third floor all floors have theremaostats

ANSWERED!

While adding insulation, I discovered an uninsulated opening between the ceiling of the basement and the floor upstairs. After adding insulation, the cold room is at least 5 degrees warmer, if not more.

When the house was built, it was properly insulated per the code in effect at the time. It had a wood burning stove in the basement to supplement electric baseboard heat.

During the winters, the kitchen became quite cold. It was located some distance from the stove on the upper floor. And next to the cold basement.

To allow more of the stove's heat to reach the kitchen, the insulation was removed from the basement ceiling under the kitchen floor.

Assume it had some positive effect.

Later, an oil furnace was added along with associated plumbing to replace the electric baseboards with hot water. And the wood stove was taken out.

At that time the cold bedroom was discovered. Since it was unoccupied, not a big deal.

Then we needed to make full time use of it, again.

I didn't know the history when I added insulation, fixing the problem.
Was then given the history and all fell into place.

"And next to the cold basement."

SHOULD HAVE READ

And next to the cold bedroom.

I have a hot water baseboard system in my house. When I purchase the home it had one zone for the entire house. Since then I have added two additional zones by installing thermostats and zone valves in strategic locations. These modifications worked well for a couple of years. However, recently the zones are not functioning properly. When the thermostat calls for heat the zone valve opens, then once the set temperature has been obtained the zone value remains open. This causes the temperature to continue raising in that zone. I then have to reset the thermostat to a setting higher then the room temperature. This causes the zone valve to actuate to the closed position and back to open in one continuous cycle. I then reset the temperature to the normal setting and the valve closes. After this the valve functions properly. This phenomonom is sporadic and can happen in any one of the zones. I am unable to leave the house for any extended time in fear the heat will come on and not shut off. I recently replaced all thermostats but the problem still exist. What can I do to resolve this problem?

Bigred04,
It would be much easier to help you if you would be kind enough to start a new thread with your question. Entitle it something like "Zone Valve problem, hot water baseboard".

Thanks, Grady White