Only 1.5 rads warm up after draining,boiler switches off!!!!

[ProfessionalPlasteringSer]

hi, i'm new to the forum, looked everywhere for info could find it so thought id join and start new topic!!
I added sentinel central heating cleaner, drained the system and removed a rad in the bathroom to change it to a towel rad. now i've put new chrome valves on in the bathroom but havent put the rad on yet. allowed the system to fill, added some inhibitor, and turned it on. the hot water is fine, but only one rad warms up, and 1 only gets luke warm, and the boiler switches off after a couple of mins, i've bled the system and the pump. Its a oil boiler, i think the pump is fine as pipes get hot as far as i can reach, even though its only on for a couple mins, the house is a bungalow, dont know about the valves. another thing is that there was no drain cock on any of the rads, i know a couple of rads where removed few years back for fitted furniture and presume the drain cocks went with them!!!! i added one to a random rad nearest the back door whilst the system was empty (dont know if this was the lowest point) any help much appreciated,

cheers in advance

John @ PPS
P.S im a plasterer, specialising in damp-proofing solutions and am happy to get into the forum spirit so happy to aid any damp issues!!!

 

[sloppytom]

How old is the system?

 

[ProfessionalPlasteringSer]

Not to sure, its in my mums places, she had the pump done a 4 years back, don't know about valves or boiler. Though I don't think it is very old. This morning the rads where a bit warmer, but only 3 of them. Guessing its sludge, so going to try and flush it again! Any thoughts. Cheeers