Leaking pump part - do i just screw it tighter?

[bananax]

Hi guys, i hope you can help:

My boiler is old ( Vaillant VCW sine 18 ) but has been working beautifully for years. Today it started leaking (hot water), quite badly, from what looks like a little valve / screw on top of a little cylinder (hot to the touch) whenever the boiler is on (for either HW or CH or both). This small cyliner is attached to the back of the pump and is easily accessible.

I have attached photos.

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• bananax
• 21 Mar 2009
• 1

Untitled

• bananax
• 21 Mar 2009
• 1

Untitled

• bananax
• 21 Mar 2009
• 1

My question is, do i just tighten this screw? or clean it or something easy? Or do i need to get a boiler technician to look at it (wait a minute, that's you guys i hope!). Please let me know if it's something straightfwd - i'm capable.

Thank you very much for your time.
Marios

 

[nickso]

ideally you need to change it, it just screws out once you have drained the boiler.

you can close it until you get a replacement organised. the worst that will happen is an airlock in the pump/boiler.

 

[gorepairs]

The part thats leaking is known as a A.A.V or Automatic Air Vent. You could strip it down and see if the balls sticking because of sludge or (and probably your best bet) just replace it. Hope that helps.

 

[bananax]

Crickey nickso, that was quick! Thank you!
A couple of questions - i hope you don't mind:

Do you know why it is leaking? can i assume that's an air bleed point? So do you know why water is coming out? Any idea of cost to replace? That part alone? or whole pump?
Finally, i don't want to cause further damage - airlock sounds nasty! Is it???
Thanks again! Much appreciated!
Marios

EDIT: THANKS gorepairs! You guys have been very very helpful / quick!
gorepairs, do i need to drain the boiler in order to clean the part?

 

[gorepairs]

Hi Marios, yes you will have to drain the boiler either to repair or replace the valve. But that shouldn't take too long as it's a sealed/pressurised system.

 

[nickso]

its leaking due to old age and dirt. easier just to replace than faff about cleaning it, they are pennies to buy.

 

[Gasguru]

I suggest you obtain another AAV (standard Caleffi), remove the top part just replace that (the knurled part seals with an O ring).

Looking at the scale around the fitting I wouldn't risk replacing the whole part (I've had the valves disintegrate leaving the threaded part still in the pump, even after copious quantities of WD40).

 

[bananax]

gorepeairs, nickso, gasguru, thank you all.

Great advice gasguru, i was worried about that too - so will just replace the top part. Hopefully, that's all it is.

Weird thing is I had the whole diverter unit changed only a week or so ago, and it was running perfectly, no leaks, no issues, and suddenly - major leak from the AAV. Weird. As temperamental as the mrs!

If it starts to give me repeated problems, it may just be time to retire it. If that happens, I'm thinking of another Vaillant, but the ecoTEC pro 24 (it's only a small 1 bed flat, and i'm going to rent it out so need something cheap and easy to manage). Any strong opinions against this boiler?

Thanks again all. I'll let you know how I go with the repair tomorrow.