Heater not working - E39 M54b25

[jaredmac11]

2001 525i m54b25, 160k miles

Hey all,

I cant seem to get my heat working. I turned the cabin temp to 75 expecting heat and nothing. Eventually cranked it up to 90 and still nothing. I felt the passenger side vent and that one was actually blowing heat. I figured it was a bubble in the heater core, figured it was possible I didnt have it on all the way when doing the coolant last year. I fully bled the system (I think?) and still no heat. I will get waves of heat at random times, like if I push hard accelerations. Mostly nil

I had a bad FSU so that was replaced last week. Coolant was bled. thermostat is less than a year old. Im thinking buildup in the heater core also. Is there anything else I can test? Usually heating is pretty damn simple. Never really have issues in my other cars...

[Hakeem530i]

So one side is blowing heat and one isn’t? Is the dial in the middle of the vents set to “red”?

Sounds like the heater control valve.

[jaredmac11]

Yeah it's set to red but honestly it's been so inconsistent I'll sometimes get heat at both like when I was bleeding. But 90% of the time nothing

[effduration]

simple/obvious stuff:
-make sure there is the proper level of coolant. too little will result in symptoms you describe.
- unlock the hidden menu on your cluster to show actual coolant temp (menu 7 after unlock). I recently had your symptoms, and my car would run at 78-80c- too cold. I replaced thermostat and all is good. I know your t-stat is newer, but test coolant temps anyway.

I have heard of a couple of heater valves failing this season. I hear if you unplug the heater valve it will default to open position - can anyone confirm this?

feel heater hoses going into heater core from engine bay.

[edjack]

I have heard of a couple of heater valves failing this season. I hear if you unplug the heater valve it will default to open position - can anyone confirm this?

That's what I've read.

Have you done any cooling system work recently?

[Santaclaus4]

My heater valve assembly failed a couple months ago. Unfortunately I can't rememember what the default position is. I think it probably is the open position.
The valves can also get stuck closed.
Wait... I do indeed think the default position is "on" or "open".
When mine failed last summer, I couldn't turn the temperature down. Basically the heat was on full tilt. I could only adjust fan speed and change the center vents to "blue".

[jaredmac11]

Its not the heater valve assembly (yet). I checked coolant levels and bled the system a bit more this morning and heat is now working. Takes a wee bit to get hot, even in 50 degree weather so Im sure the heater core needs a good cleaning. Ill look out for the heater valve assembly as well.

Did you buy new? They look pricey.

[Santaclaus4]

Yea, brandy new from FCPEuro. My heat now works better than it has in a couple years.

[geargrinder]

Yep. I say heater valve. Don't forget there's 2 heater cores really. Would be nice if the outlets were such that you could swap L/R hoses and confirm (i.e. make the working side switch sides...) but I don't think they'll reach. I think you can get rebuild kits for them but that is predicated on it being a valve side fault and not a solenoid fault. I've never had trouble w/ mine so I'm not really asspurt on 'em.

- - - Updated - - -

Its not the heater valve assembly (yet)..

Why do you say that? Cuz you got heat on one side? Its a double valvey, drivers-side & bitch-side. One side easily/usually can fail first.

[Santaclaus4]

Why do you say that? Cuz you got heat on one side? Its a double valvey, drivers-side & bitch-side. One side easily/usually can fail first.

That's exactly why I say my heater is working better than the last couple years. My passengers often complained of being cold. I even noticed the lack of heat on the passenger side sometimes. I just ignored it until it failed (full heat valve open) on the drivers side during the summer. Yea, friggin hot even with the A/C full blast cause it can't cool as much as the heat can heat.