Vaillant Ecomax expansion vessel fault?

[bodgit]

My Vaillant Exomax 835 is losing pressure and I have top it up daily to 1.0 - 1.5 bar to use it. Water coming out of the overflow outside (did the bag on pipe test) so i believe it to be the expansion vessel. I turned off the boiler, emptied the water down to 0 bar and depressed the schrader valve - no water just air.
I pumped up the vessel with my (admittedly cheap) foot pump which showed 0 continuously on the gauge, but the gauge on the front of the boiler increased (is this supposed to happen?)
When I removed the pump fitting, the valve continued to leak air slowly - i had a poke st the central "nipple" with tweezers and stopped it leaking. Bar showed 0.8 on front of boiler so i restarted the boiler, but after a while the bar reading is back up to nearly 3.0. Any ideas?

 

[bodgit]

I understand that I can buy a replacement Schrader valve core from Halfords, but is it the long or short core?

 

[SimonJohns]

I understand that I can buy a replacement Schrader valve core from Halfords, but is it the long or short core?

Don't play with it. Save yourself money in the long run and get a GSR around. Won't take them long

 

[bodgit]

Thanks, it's just that I'm still trying to diagnose the fault and rule out some possibilities. I believe that it's either the expansion vessel or the valve on it.

 

[SimonJohns]

It's the complete unit. And if you have a GSR in they will be able to do it the cheapest and safest way.

 

[bodgit]

Any idea what the cost of replacing the expansion vessel will be (vaillant ecomax 835)?

 

[SimonJohns]

£150 ish

 

[bodgit]

Cheers

 

[jtsplumbing]

Q" Did you open the prv wile you were pumping up the tank ? you need to do this to clear the water out of exp tank

 

[southcoastboile]

needs a new prv and vessel idealy, if you were recharging it and the pressure on the boilers gauge was rising then you haven't done it properley, you need to keep draining it untill the gauge on the boiler shows 0 and the vessl shows 1 or whatever it needs to be charged to, just change it, if the vessel has lost its charge theres a reason, its faulty, ive never had one that hasn't lost it again after a few months weeks or days, the hose could also be blocked up to the vessel, you should get a gsr engineer round to look at it, if you dont no exactly what you are doing you could do more harm to the boiler then good. Could be the schrader valve if you are lucky and you won't need to change anything but doubtfull. prv will probably not reseat now so that will need changing.

 

[bodgit]

Many thanks for the info, it seems to have settled down in the last couple of days - not had to top up the water for the first time in a week and pressure back down below the 2.0 bar level. Probably a false dawn , but heating engineer coming tomorrow to service it so i should have a better idea then.