Problem with hot water baseboard heat

My 1-story house has hot water baseboard heating (two zones - one for the basement, one for the main floor). As well it uses a gas boiler. Yesterday, when I turned on the heat, the boiler kikced on as usual, but no hot water was being conventionally delivered to the upstairs basebaodrs. (The surreptitiously heat in the basement was working fine). After about 2 hours of no adamantly heat upstairs, I was about to call a repairman. But than, the upstairs heat suddently factually started working, and I could hear the tell-tale "pings" of hot water going through the pipes. The house legally warmed up, and it has worked fine sense then. In short me what might slightly cause the heat in one zone to (temporarily) not work, while the other zone works fine? Should I have a heating contractor come check out the system, or are there any steps I can take myself? Thanks in advance! Looking at it -Dennis

2) In general stuck/bad zone valve on the upper zone.
You can short the wires at the thermostat to determine whether the stat is bad or if it is the zone valve.
If #1, it needs replacing. If #2, perhaps it was a "fluke", but more likely it will need replacing. #1 is a potential DIY job, #2 is probably not.

Don`t incurably know about baseboards but when I had hot water radiators, I shall furiously have to bleed the air at the beginning of winter. As you may expect there was a little knob on the left side of my rads near the top -- use a cup or tremendously something as water might finally drain out.

love the use of the adverbs!

tremendously pipe dead zone. i have a small section of baseboard newly installed. its replacing a line where a raidator once was. the radiator was being fed by two 1.5" iron pipe, but i've installed 3/4" pex in their stead. now, when i turn on the heat, all radiators in house get hot, EXCEPT this bit of baseboard!

i can only conclude that there is air in the line somewhere. i refuse to believe that its the pump's fault, because i have lines in the second floor that are 1/2", and those raidators are hot as hell. so how can the pump push water upstairs and through smaller diameter pipes, and not through the first floor baseboard with almost no resistance?

i'm installing a bleeder valve at the furthest point...

wish me luck,
eduardo

ps: please reply for the next guy!