What's the second most common cause of 'no heat' in a Z3?

[htroberts]

As it's gotten colder this season, I've noticed that I have almost no heat in the Z3. The most common cause appears to be entrapped air, and although the reservoir needed about 1/3L to top off, I'm pretty sure I don't have any air. I followed the bleed procedure, and no bubbles are is coming out, only liquid coolant.

Oddly, I seemed to be getting quite a bit more heat running the motor at idle with the cap off than I get at highway RPM/speed. Maybe because I have no (cold) ram air coming into the radiator?

The car also seems to be running slightly cooler than it does in the summer, according to the temp gauge--in the summer, the needle points straight up, and now it's about 1/3 of the way between straight up and the index mark to the left of center. I understand that the gauge is computer controlled and doesn't move linearly with actual coolant temperature. This makes me think the thermostat is partially stuck open, but I thought I'd ask...

I've got just under 90k miles, and have not (yet) replaced the water pump, although I'm planning to soon.

Thanks,
Heath

[07090]

Failed water pump?

[bimmerbri2]

Does the air temp selector knob turn easily without any resistance? If so, it could be that the lever behind the knob and sheared. I just had to fix mine about a week ago.

[328 Power 04]

Failed water pump?

A failed water pump would definitely overheat the engine.


I would say thermostat is your issue. I know that my z3 has that problem, and it awaits a thermostat change.

[dkindig]

It's common for the thermostats in these cars to go bad. In the summer ambient temps are high enough that it isn't as big of a factor but in the winter the temp guage will act as you described, not coming all the way up to normal position because the thermostat hangs open.

Replace your thermostat and all should be well...

[Kyle Anderson]

I'm also thinking thermostat.

[E36ic4Me]

I would say thermostat is your issue.

That'd be my guess as well. My 96' runs cool and the heater isn't near as effective as it should be. I gotta get off my butt and do a thermostat change!

[BimmerBreaker]

If the car isnt getting up to temperature it will not have enough "extra heat" through the heater core to heat you. Same reason it takes awhile for hot air to come through after a cold start.

I dont think its the thermostat. Is the heater core clogged? It seems like at idle while there isnt extra air going through the radiator that the car gets closer to "at temp" and then you have heat, whereas when driving its cooling dare I say "too efficiently" and it doesnt have the extra heat.

Im sure if I stated some of my car's behaviour here people would blame the thermostat, but I know its fine - it reads accurately, if I drive hard the thermo and the oil temp will read dead center, otherwise at low-rpm around town driving my oil temp is at the first tick and my thermostat never gets to the "middle" - but I do still have heat, which is why I say look at your heater core.

[BlackjackM]

Your thermostat is stuck (failed) open.

[htroberts]

Does the air temp selector knob turn easily without any resistance? If so, it could be that the lever behind the knob and sheared. I just had to fix mine about a week ago.

It does turn freely, but not that freely. And there's a definite difference in the temperature of output air between when the selector is on cold and when it's on hot.

[MrTorque]

Could be a stuck water valve (aka heater control valve). 64 11 8 375 443

[Mr Bingley]

Could be a stuck water valve (aka heater control valve). 64 11 8 375 443

+1

[dinanstu]

Could be a stuck water valve (aka heater control valve). 64 11 8 375 443

How does that affect the engine not getting to operating temperature?

I go with .........thermostat stuck open......

[MrTorque]

I believe it effects the flow of coolant to the heater core. No hot coolant equals no hot air.

[dinanstu]

I believe it effects the flow of coolant to the heater core. No hot coolant equals no hot air.

True, but the caveat is the engine isn't getting to temperature....thermostat....

[eas1974]

I had air in my coolant lines. Take it to a shop and they can force the air out!!! He comes right back!