My vaillant 824/2e ecomax on start up has fast rise in temperature up to between 80-104 c and pump stops. central heating pipes are cold by boiler and there is only a bit of hot domestic water before it goes cold, because the pump stops.
A plumber has replaced the pump, but this did not solve the problem.
The heat exchangers have been removed and do not appear to be blocked.
Can anyone please help?

scott, March 2012

I had a similar problem, where the temperature would rise to over 90 degrees and the the burner would stop. Initaially thought it was the divertor valve as Central heating would be on when only the hot water was selected. Turns out there was sediment in the boiler that was restricting the flow. Squeezed the rubber tube inside the boiler and felt the crunch of the sediment. Found this out after power flush was conducted. So check that first, I'd say

Sidder, January 2013

Could be faulty boiler thermostat causing early cut out although diverter valve seems more likely or sludge build up or limescale. You could try a descaling solution and system flush . The process is too long to go into here and takes time and patience to do properly but it can be done D.I.Y. but you can get info from various how to sources. Try the library D.I.Y. section or B&Q how to leaflets. Good luck.

John Mantova, March 2012

diverter valve is faulty

ltd, March 2012