Radiant Heat questions

All,

First time poster here.

We have owned our Eichler for 5+ years and during that time seen the heating efficiency of the radiant heating system go down. Nowadays, it is not able to hold the house temperature at even 63F. In the past it did better.

I hence tried to understand the various components. One thing I am finding is that the copper pipe leading into the slab is not particularly warm to the touch (and the temp meter reports sub 100 F temperatures). In addition, the exhaust for the flue gases leaving the boiler is hot. To me it suggests a bad pump or a a clogged boiler. Not sure which one. Any ideas on how to determine if the pump is working or not? It does hum when its turned on - just don't know if it is pushing any water.

I have to admit that these past 5 years I never paid attention to it. Infact I did not even know that the pump I had was one that needed oil every year for lubrication - so I never lubricated these past 5 years. Could it be that the pump is hosed?

Any thoughts on how I should proceed are welcome. I am a DIYer, so would prefer to troubleshoot myself, if at all possible.

Thanks