Z4-forum.com

Its a 2.0i, 2005 and I know some on here just love them!
Symptoms:
Heater only blows cold air. Apart from De-mist setting which then only gets 'warm' at best on the driver side.
A/C works but only from cold to ice cold, no heat.

Checked and OK, even double checked:
Bled coolant (on steep drive) twice - no air at all and level as should be
Engine reaches and maintains temperature
Felt, squoze both inlet and outlet pipes to heater matrix - both hot and even
No drop of coolant level at all

No smell of coolant in car even after a long drive.
Theres no issue with temperature or overheating so I'm ruling the thermostat out.
I'm aware these models use an auxiliary motor just for the heater matrix but would I still have even temperature on inlet and outlet if this has failed?
I have read the heater has 'blender' flaps which have been known to cause this but does anyone on here know of this being an issue?

Not sure where the issue lies so anyone's input is appreciated.

I'm able to carry out the motor swap myself and these are relatively inexpensive so may try that first.

Also, could I still get a flow and even temperature through matrix if it's blocked and needs backflushing?
I can easily do that using hose clamps then re bleed the system a couple of times.

Thanks in advance

I'm afraid I can only offer the tiniest of help. Many years ago I had a similar problem in a previous car. It wasnt the coolant at fault. I think it a was a thing called a Heater Control Valve which had to be replaced. I'm not sure if these cars have one.
....
A quick google later and, yes they do. I found parts stores selling them and youtube videos on how to repair and replace them. Maybe this could be your problem?

These cars don't seem to have a water mixing valve, but there is an air mixture flap actuator drive (servo motor). One thing to check. There are even more of these actuators, each for different functions. You should be able to test move them with a tester. Are there any faults on a tester anyway, have you checked?
Another possible thing is an additional water pump your car should have. But I doubt this would cause your issue since your pipes are all hot.
The last possible cause would then be a blocked heater radiator. It might be letting hot water just pass by but not heating up itself.

Gebbly wrote: ↑Sat Jan 11, 2025 12:22 am I'm afraid I can only offer the tiniest of help. Many years ago I had a similar problem in a previous car. It wasnt the coolant at fault. I think it a was a thing called a Heater Control Valve which had to be replaced. I'm not sure if these cars have one.
....
A quick google later and, yes they do. I found parts stores selling them and youtube videos on how to repair and replace them. Maybe this could be your problem?

I can't find a heater control valve anywhere in part ETK, it shows direct pipelines from the engine to the heater radiator and back to expansion tank. I also saw parts stores selling them, but each of them looks entirely different. And none of the videos is actually for the Z4 or have I missed one? I guess these cars don't have this valve at all as strange as it seems not having it. Or is there a mistake in the part ETK?

It could be the flap mixture valve as suggested.

I'm thinking of trying a new (used) heater control panel as they're only cheap and easy to fit. There doesn't seem to be any sound when I turn the heat settings so might not be sending a signal to the said mixer door.

Also, these cars don't have a heater control valve as it's done via the mixer door withing the heater unit.

"I can't find a heater control valve anywhere in part ETK,"
Again, I really dont know if this is the fault but just in case you start looking in that direction I see parts in places like
Heater control valve BMW Z4 E85 2.5 i 177 HP 2.5L Petrol

And a more general rough guide, heres a chap with a different BMW actually doing a fault find and then swap of Heater Control Valve to fix a problem that matches your description.

If this isnt the fault then apologies for misleading you.

Gebbly wrote: ↑Sat Jan 11, 2025 12:11 pm "I can't find a heater control valve anywhere in part ETK,"
Again, I really dont know if this is the fault but just in case you start looking in that direction I see parts in places like
Heater control valve BMW Z4 E85 2.5 i 177 HP 2.5L Petrol

And a more general rough guide, heres a chap with a different BMW actually doing a fault find and then swap of Heater Control Valve to fix a problem that matches your description.

If this isnt the fault then apologies for misleading you.

This is an early UK 2005 2.0i model.
Thanks again, but like I said these have constant hot water from the coolant system running thru the heater core and there's a mixer actuator to control the amount of heat from the matrix to the blowers. So no in-line heater control valve on the coolant system.

Could the system need flushing or bleeding. Might be an air lock somewhere

An airlock would result in cold pipeline somewhere. But his pipes are all hot.

Gebbly wrote: ↑Sat Jan 11, 2025 12:11 pm "I can't find a heater control valve anywhere in part ETK,"
Again, I really dont know if this is the fault but just in case you start looking in that direction I see parts in places like
Heater control valve BMW Z4 E85 2.5 i 177 HP 2.5L Petrol

And a more general rough guide, heres a chap with a different BMW actually doing a fault find and then swap of Heater Control Valve to fix a problem that matches your description.

If this isnt the fault then apologies for misleading you.

But can you show me where this part is being built in the car?

Update.

Took air vent and radio out. Got right up to opening and the mixer doors are operating so that's ruled that out. Also turned every vent to closed and put heating on full and facing downwards and I have control from cold to hot (well slightly warm) albeit only on the driver's side.

I'm reckoning there's flow thru the matrix but very limited so I'm gonna back flush it next week. I'll also test the auxiliary motor while I'm at it.

Both pipes enter the same end of the matrix.
Due to poor design, sludge builds up at the far end. The water takes the easy option and simply circulates straight back out without passing through the matrix pipes.
You may be able to improve it slightly but it'll need a lot more than just a simple flush.
street rigged up an external pump and circulated house radiator cleaner through his for hours. even then i don't think it completely cured it.

enuff_zed wrote: ↑Sat Jan 11, 2025 3:33 pm Both pipes enter the same end of the matrix.
Due to poor design, sludge builds up at the far end. The water takes the easy option and simply circulates straight back out without passing through the matrix pipes.
You may be able to improve it slightly but it'll need a lot more than just a simple flush.
street rigged up an external pump and circulated house radiator cleaner through his for hours. even then i don't think it completely cured it.

That's what I'm going to do mate. Bucket of mixed rad cleaner, bilge pump and then into empty bucket backwards and forwards.

x-driver wrote: ↑Sat Jan 11, 2025 1:16 pm But can you show me where this part is being built in the car?

I'm sorry I dont really have any more info than I gave previously. I think it was a problem on my old M135i and I took it to a garage to fix rather than doing it myself.