Bleeding radiators

[Derek Porteous]

I have an Eberspacher on our narrowboat heating three radiators and the calorifier. The heat from the radiators has been falling off for the last couple of years (hot/warm at the bottom, cold at the top). Time to bleed them all.

I have had a search, but couldn't find the answers to a couple of questions,

 

I understand I should run the system for a half hour or so before I bleed the radiators and that I should start with the first one in line and works my way onto the next in line and so on. However

 

1) should I leave the pump on whilst doing this, or does that just add to the aeration?

 

2) should I turn the other radiators off whilst I am bleeding one of them?

 

Thanks,

Derek

[David Mack]

I just turn the heating off and bleed the radiators. No need to preheat, as you are releasing the air which is already in the top of the radiators.

 

If a lot of air comes out, then better to top up the header tank before bleeding the next radiator, otherwise you may end up introducing more air via the header tank connection.

 

It shouldn't matter what order you do them, nor do you need to turn any radiators off.

Edited October 17, 2016 by David Mack

[NMEA]

I would always start with the furthest away, no need to do anything other than just bleed them. You will need to keep a close eye on the header tank during the process, or make sure you top up the pressure if a closed loop system. If the system is a header tank type then bleeding may be a slow process as there is usually bugger all head of pressure. If you have had the boat a while (3 years +) it may be worth draining down the coolant and replacing with a 25% antifreeze solution as it may not be air but the gaseous products of internal corrosion.

Edited October 17, 2016 by NMEA

[Derek Porteous]

Thanks guys, My one concern now is the comment from NMEA as the system is 10 years old. I will try bleeding it only first, and then if I am not happy with the results, do a complete replacement. Thanks again.

[Neil Smith]

I would drain it down and replace the anti freeze solution as at 10 years you wont have much corrosion protection left, then bleed it.

 

Neil

[ditchcrawler]

I would drain it down and replace the anti freeze solution as at 10 years you wont have much corrosion protection left, then bleed it.

 

Neil

And if its 10 years old you probably wont know what to top it up with

[NMEA]

And if its 10 years old you probably wont know what to top it up with

I think at 10 years I'd be wanting to flush, clean and then refill so you could use whatever you want.

[Derek Porteous]

Thanks everyone. Drained down yesterday, refilled with mixture and all seems good.

[Neil Smith]

If you replace the bleed screw on the furthest rad with an auto bleed one you wont need to worry again.

 

Neil

[Bee]

If it is the other way round, i.e. cold at the bottom and hot at the top then suspect sludge, might just help someone.