No heat

Hey, my 01 525i isn't blowing out heat anymore. Just noticed the issue now since its getting colder. It was working fine last Winter and Ac was working great in the summer. Now the heat doesn't work at all. When I'm driving sometimes I'll feel heat start blowing through the vents for a few minutes but as soon as I stop, cold air starts blowing again. My temp gauge is fine, it's consistently in the center, so I know my thermostat is good. One thing I did notice though, the hose that's connected under the cowl (behind the engine) is disconnected. The cowl is broken apart worse than ever, leaving the hose to just hang. My question is does this hose carry heat?

This hose here...does it carry heat? What exactly is it for?

Sorry here it is.

Originally Posted by Sequence

Sorry here it is.

That looks more like an electrical conduit.
You're either low on coolant and have air in the heater core or your not getting hot coolant pumped thru the heater core.
Possible things to check are the heater control valves and the aux pump for the coolant.
On your car I think it's at the base of the radiator on the drivers side. Check out RealOEM, it should have a pic of these parts.
If the above are Ok, it could be your temp control panel of possibly a fuse.

JimLev's a G. I would follow his advice. When I completed the Valley Pan Job on my 540I I knew that I did not have enough coolant in the system when I refilled because hot air was not coming from the vents. I added BMW coolant, BLED the system again, and the heat returned. No SES lights and my temperature gauge was aligned in the middle just like you have described in your scenario. Now I have the drivers side cabin filter disconnected and I'm cooking inside. Back on point, an old school trick to cool an engine down faster is to turn up the cabin heat so that air blows over/thru the heater core which effectively helps lower the coolant temperature, in some manner. If coolant is low the heater core will not have enough warm/hot coolant in the heater core to heat the air entering the compartment which enters the cabin. Or, as JimLev has already indicated, a possible error in the electronic control of said process.

Either way, if this were my car, I would double check the cooling system for small coolant leaks. I don't know where to look on a 525 but sometimes you can smell the coolant from inside the engine bay. It may be proper procedure to check for coolant leaks especially if you have not added or fooled with the coolant system recently. i.e. Find out why are you low on coolant?... That is, if you are low on coolant and it is not an electrical problem. IMO the biggest give away to a coolant leak is the smell. Honestly, let her cool down, FOLLOW THE BLEED PROCEDURE, and test the heat again. I think she may be fine. Your feeling heat while driving because the water pump is pumping the coolant to your heater core with greater force as the RPM's increase. My two cents.

Originally Posted by Sequence

Sorry here it is.

That's electrical. There is one off the back that carries hot coolant to cabin heater valves, but that's not the issue, rather you need to bleed the radiator & if problem keeps coming back, you have coolant leak and/ or cracked head.

Thanks fellas, this is all great advice. I'll take time tomorrow to track down the problem and report back.

FWIW, I didn't have heat (or it would take a while to show up) and it ended up being the upper coolant hose (small crack).

Finally got around to checking everything today. I was just really low on Coolant :/ ...no leaks or anything that I could see. I bled the radiator, topped it off, and was on my way! Thanks for all the help guys.

Originally Posted by Sequence

Finally got around to checking everything today. I was just really low on Coolant :/ ...no leaks or anything that I could see. I bled the radiator, topped it off, and was on my way! Thanks for all the help guys.

And you weren't getting a low coolant light?
Or doesn't this model not have a coolant level sensor?

Originally Posted by JimLev

And you weren't getting a low coolant light?
Or doesn't this model not have a coolant level sensor?

I can't speak for the OP, but I know there's no low coolant indicator on my car (525 w/ low OBC) - at least not one that functions. I can see the dummy light in the dash, but it doesn't do anything.

Yeah I never got a low coolant warning in the dash, I don't think there's one in this model. I'll check the manual to make sure.

Nope, no low Coolant indicator is on the 01's. Only coolant info it says is to mix 50:50 water and anti-freeze to protect against lower temperatures and replace coolant every 4 years.

My current NO HEAT problem is an intermittent one. My heater either works perfectly or blows cold. It may have something to do with engine speed. It blew cold while the car was idling at my daughter's school with the temp gauge at the mid point. It blew cold regardless of the dial placement (the easy-tuning dial between the center vents on the dash), regardless of how hot i set the cabin temperatures, regardless of whether the system was on auto or manual directed at feet or body, and regardless of how loudly i cursed at at it. It blew cold for the entire 1 mile drive back to the house without a hint of warmth. After some forum searching, i went back out and tried the REST button (i hadn't known before what it did...coool capability!) and it still blew cold. My temp gauge is just right...at the mid point. There is no sign of coolant leaks (newer radiator, water pump).

Half an hour later i had to run my daughter back to school. I took the car down a road where i could give it some gas and i had good HOT heat. Parked in front of the school at idle for a few seconds (i turned off the car to go in and see the turtles) there was still heat (though maybe not as hot). Still had heat after starting the car again and waiting for passengers to put seatbelts on (though maybe not HOT) and had good heat on the trip home without giving the car any significant throttle.

I know its a very basic question but how do you know if you're low on coolant? I am not getting a warning light (and am proud that i've been without any warning light for some time...though i hesitate to actually acknowledge it).

Thanks for your attention. The forum is of immense value.

Wait until the car is COLD (let it sit overnight) and open the cap on the expansion tank. There's a red plastic float in there. The top of it should be even with the top of the tank. If it's low, there's a bleed procedure you should follow to add more. Here's what I did... Put the cap back on but not tightly. Turn the heat up all the way and start the car, revving it to about 3-4k a few times and shutting the car off before it starts getting warm- no longer than about 30 seconds. Add coolant until the float says it's full and close it up. Drive normally the next day and check it again when cold the following morning. If you're low again you probably have a leak somewhere. My car does not have a low coolant warning, so I never knew it was low. Good luck!

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Well now I'm starting to smell coolant occasionally while driving. From my research it sounds like it could be a leak. As hard as ive searched, I can't find any leaks though. However I checked under the hood after a quick 10 mile drive one day, I saw that there was a very small streak of dried up coolant on top of the radiator. Only thing i can think of is that i needed to bleed it more. Am I overlooking anything?

smelling coolant inside the car can be a bad sign. i had this happen in an audi 5000 quattro (great car though rediculously unreliable!) and it turned out to be the heater core (what in those cars was a pretty common problem). It was a lot of shop hours to replace in the audi and suspect it is a J O B in the bmw as well. I thought my heater core was bad in my 2000 528iT and purchased one...turned out i didn't need it. I still have the core and would give you a deal on it if you need it.