# Bleed your thermosyphon!



## Taff (May 5, 2015)

Did this on the francino classic I'm rebuilding and was amazed by how hot the group head got. Had never done it on my magister.. until this morning. Really glad I did. Must have been an airlock somewhere as I've had to turn the pstat down quite a bit to keep the grouphead temp where I want it. Seems much more stable during a shot now too.

Why/ how do they get air in? Any ideas how often this should be done?!

Ta!


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## jeebsy (May 5, 2013)

How did you do it?


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## Taff (May 5, 2015)

@jeebsy when the machine is hot, crack the top nut on the boiler (on the pipe join from the boiler to the group) half a turnish. Tighten when hot water comes out and not steam/ gas. The magister is not e61 so on that I also did the joint into the group afterwards as it's higher than the boiler outlet. Machine now behaving very differently, idle temp is super stable and group temp rises a lot faster during flush!


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## bronc (Dec 10, 2012)

Wouldn't the air come out when you let water run through the grouphead?


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## Dylan (Dec 5, 2011)

bronc said:


> Wouldn't the air come out when you let water run through the grouphead?


I guess, like a home central heating system, air can become trapped at high points in the system.


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## Taff (May 5, 2015)

bronc said:


> Wouldn't the air come out when you let water run through the grouphead?


I don't necessarily think it does as the thermosyphon loop is like a tube in a tube. Happy to be corrected, but I think the thermosyphon and delivery loops are separate some or all of the time.


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## Dylan (Dec 5, 2011)

Taff said:


> I don't necessarily think it does as the thermosyphon loop is like a tube in a tube. Happy to be corrected, but I think the thermosyphon and delivery loops are separate some or all of the time.


I dont think this is so on most machines...

My VBM feeds cold water into a thick single tube within the boiler, this feeds the group which then feeds back into the boiler. No double tubing.


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## jeebsy (May 5, 2013)

If there's air in my Expo (eg if i disconnected the water and braided hose was empty before i reconnected it) it can sound like it's sneezing for the first 20 or 30 secs the pump is on but it (seems to) work its way out itself


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## Taff (May 5, 2015)

I've possibly got it a bit wrong, but im sure I had air in both my loops. Some further reading:

http://www.frcndigital.com/coffee/stall.html


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## Dylan (Dec 5, 2011)

Ah, sorry yea I misunderstood what you meant. My machine does indeed have that 'tube', but I am confused by what you mean by the thermosyphon and delivery loops being separate.


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## Taff (May 5, 2015)

I'm quite surprised at the difference this has made. I was doing big flushes before as there was a lot of steam coming out in the flush. What I now think was happening is that there was some local boiling in the HX, which means the flush water was noisy and steamy.

This is now not the case, and extraction seems better now - maybe some trapped air was still causing local boiling during the brew cycle. Taste is better, and extraction in the naked is much more even.


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## Dylan (Dec 5, 2011)

Not in any way doubting that it has made a difference! Just curious


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## jeebsy (May 5, 2013)

Interested in this too, always just assumed air would work itself out. The equivalent bolt of the group of my Rancilio wouldn't budge when i stripped it down


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## espressotechno (Apr 11, 2011)

The Fracino Classic "airlock" is well known in the trade. The airlock is due to the design of the top HX pipe. On newer machines I think Fracino have managed to solve the problem.

I haven't come across this problem with other brands using the E61 head, in my travels....

Rancilio, Magister, Cimbali don't suffer from HX airlocks.


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## Taff (May 5, 2015)

@espressotechno interested in your take on why this has improved my machine.. surely there is the potential to trap air in most systems somehow?


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## espressotechno (Apr 11, 2011)

On the Fracino Classic the upper HX pipe has a slight "swan neck" on it which causes an airlock to form - usually after an overhaul or if the machine has been transported & manhandled a lot.

Other machines tend to have a steady incline on the top HX pipe, from boiler to grouphead. So any air bubbles get flushed out at the grouphead.... I have not yet had to de-airlock any other makes of machine (keeps fingers crossed).

PS When doing the Fracino Classic airlock removal, stuff an old towel down the front of the boiler to soak up any escaping water.


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