Help Needed With Heater Problem

[Jeff & Jo]

I recently bought a 1991 300CE and the only issue with it involves the heater. The heater blows cold until the car is in motion and then it appears to work fine. My instinct tells me there is probably some sort of restriction going on here... the main water pump replaced 2k ago. I plan to have the system back flushed under pressure to try to clear out heater core. If this fails, I thought of checking the 2 auxillary water pumps next. How is this best done? Also, any other ideas/thoughts on this? Could the mono valve be the culprit? Many thanks to all in advance,
Jeff & Jo

[taker22]

this is normal. not to worry. heat doesn't come on until coolant temperature rises to a cetrtain level. don't start back flushing systems uneccessarily.

[TX76513]

Also...check you coolant level. Sometimes simple is overlooked