Help! Heating acting up

I'm sorry for the long message. I really want to avoid having to bring a 'pro' to check this out, so I want to exhaust my capabilities before I have to shell out lots of cash:
The whole second floor of my house is frigid. I have a oil based boiler (replaced new in late 2004), and the system is water based (hot water flows into the radiators in the house). It has two zones, the first floor and the second floor, controlled by separate thermostats.
Problems started a few weeks ago. Temperature was erratic upstairs. Sometimes we'd set the thermostat to off and upstairs would be boiling. Other times the thermostat would be high and heat would be non-existant. Most of the time it worked fine. We still had the thermostats from the older boiler (20 y/o at least) and after tinkering w/ the temperature one day the front plate fell out (w/ the thermometer coil) and heating stopped on the 2nd floor altoghether. I replaced the thermostat w/ a nice new digital one (24V compatible w/ my unit), and connected the R and W wires just as they were identified in the original thermostat. Heat never came back to the 2nd floor.
The boiler is in the basement. (As my install guy explaned it) the heating water coming out the front pipe, splitting into two, and one going to the first floor zone, the other going to the second floor zone. After the water makes it's way around, two pipes come back down to the basement, each with a small pump. These pumps are hooked up to the box that also connects the cables from the thermostats. The pipes after the pumps join into one pipe and go back into the system. This is the loop of warm water. Touching the pumps they are both running.
I noticed the back pipe coming down from the second floor was cold, while the one coming down from the first floor was hot. I took this to mean that the hot water wasn't making it's way around the system. I 'bled' the system to get rid of air in the 2nd floor zone (you could feel air being forced out the pipes while it was being 'bled'). Now both pipes are warm, which is good... but no heat upstairs yet!
Tracing the front pipe that pushes water from the boiler into the upstairs rooms, I find that it starts off scolding hot, and the first floor section is scolding hot all the way till the pipe leaves the basement. Following the split for the second floor, it is hot initially, but as I move farther away from the split it gets cold (even before it leaves the basement).
What the heck could be going on? Could it be the thermostat causing issues still? Tomorrow I'm going to pick up a voltage meter and make sure the connections are good. Apart from that, what else could be going wrong? I was quite surprised that the 2nd floor front pipes were cold, given that the corresponding pipes at the end of the loop (w/ the pumps) were warm. I made sure my installation guy explained everything to me. Could I be misunderstanding how the system works? How could there seemingly not be any hot water going up to the second floor, but the pipe at the end of the loop is warm? Is the loop flowing the other way instead (pumped up the back?)? The manual for the unit is useless.
Ok... that's about it. I'll be eternally greatful for whatever guidance you can give me.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I agree with Paul's advice. I want to add one more thing. The boiler was recently installed you say? I would think the installer would come back and take care of any problems that may show up. Try the bleeding as that is simple and free, but don't hesitate to ask the installer for help. He may have bled the system originally, but it just needs more or some sort of adjustment.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 1/8/2005 12:58 AM US(ET), coldguy took fingers to keys, and typed the following:

zones (floors)? If so, the following pertains to my Honeywell zone valves, yours may be different. I have had to replace the whole zone valve in one case and in a couple of other cases, just the electric motor because the motor's brass drive gear had worn out. The zone valve is a square box mounted in the hot water lines going to each zone (floor) and has wires going into it (in my case, at least, 2 red and 2 yellow). You may or may not have a manual lever on the bottom that can be set to 'auto' or 'open'. If you do have the lever, push it all the way to the right and then pull it towards you a little to get it into the lock notch to keep it open (look underneath to see how to lock it). If the top floor then gets hot, you have found the problem. The problem with the valve could be electrical or mechanical. If the electric power is getting to the valve motor when the thermostat is calling for heat, then it is probably mechanical. If you feel adventurous, Turn off the boiler with the emergency switch, and then pull the cover off the zone valve (it should just slide off when you pull on it, in my case anyway) Unhook the wires to the motor and remove the motor (just 2 screws in my case). Observe the motor gear. If it has a worn groove around the circumference, you probably only need to replace the motor. I don't know if you can get just buy the motor, but I have bought the whole valve and just used the motor from it. I have a couple of new motorless valves in case the valve ever goes. It the gear looks intact, the whole zone valve will probably have to be replaced (Plumber time!). Put a new motor in the valve, wire it up, and see if that corrects the problem. If it doesn't, call that Plumber.
--
Bill

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.