Z3 Heater or is it just me.

[Mnbrennan]

I'm a little late to the party, but if anyone found the right answer, please share. My heater heats fast and is quite hot, except when I stop for a light and am at idle, then it cools almost immediately. If I let it idle for 10 minutes without the heater on and the fan on high, it will over heat.
With the heater on or off, it will overheat without the fan on high. Past experience tells me the possibility of a damaged/worn water pump are at least 90%. I have had a few vehicles in the past with the same symptoms, both were water pumps. Any input?

I have the same problem on the smurf, when it's idling its goes lukewarm but it hot when moving. I've heard that the heater control valve stops the flow when below a certain rpm but I've not had this issue on any other zed

 

[Sam Schwartz]

Thanks... i would go straight to the heater control valve if it wasn't for the overheating issue at idle and the heater fan off.... I'm thinking the worn water pump (possibility) is not creating enough pressure at idle to activate the control valve, but at higher RPM's more pressure is created, opening the valve. 100,000 miles ago the heat was hot at idle, so I am thinking (oh, oh) it's not a design defect. I'll let you know if the water pump fixes anything...

 

[Andy-M]

Funny thing the Z3M come with a additional pump built into the heater control valve which makes me think there must be a problem.

 

[Sam Schwartz]

Could be! Because of the overheating at idle, I am replacing the water pump first. I talked to a couple of real auto part store salesmen, and they are pretty sure that year z3 doesn't have a pump built in to the heater control valve. I'm not sure how accurate they are... As far as I can tell it has two solenoids, a 3 wire plug and a manifold.... I'll let you know ...Thanks!

 

[Andy-M]

Water valve with additional water pump part no 64118369807 is fitted to some Z3M's