vauxhall vivaro heater takes a long time to heat up, but when it does it runs okay, untill you hit standing traffic and it go's cold??

simmo, December 2010

sorry can't help, on here to solve my similar problem.
even when my vivaro is fully warmed up, i only get warm or hot air when engine is kept above 2k revs.
tried bleading it from the thermostat housing as well as the other 2 bleed pipes and still no luck.
can anyone give any advice.
thanks in advance.

sid, December 2011