318ti heater blows cold

Hi Last winter I froze as the thermostat in my 99 318ti was open and the car never got warm. a few months ago I replaced the rad, water pump, thermostat, hoses. I followed the procedure to bleed the coolabt system. The car was much happier and it started running at a decent temperature. The heat also worked really well. Two days ago the stopped. It only blows cold air now. The car is still getting up to temperature. Any suggestions? Its really cold.

Did the cable to adjust temperature snap?

It doesn't feel any different than before. I don't think I turned it off hot in the last week.

Inspect the wires going to the heater valve. If you don't find a problem, get a multimeter and see if you are getting anything through them. If they are fine, maybe that expensive ass valve is out.

Coolant level ok?

The thermostat housing cracked?

If you grab the hoses going into the heater are they hot? There are only two real issues that can cause this.
1. Core is not getting warm coolant.
2. Air is not blowing across core into car.
First check to see if both lines are hot. If they are then coolant is circulating in the core. If not then check the valve/coolant level and all of that (actually, check coolant level first just because) if fluid is circulating then you need to check whatever system of doors your car has. I have not advice for that other than to manually set them to hot and don't touch them until spring when it's warm enough out to actually work on a car.

At least you still have a heater core.......

check the coolant level. It sounds like you have an air bubble in the system.

btw, when I had my Ti, I -never- bled the system, I would just pop the bleed cap, fill the system till coolant was visible through the hold where the cap went, close everything up, and go along my way.

Had the same problem in mine. There's a TSB about the bowden cables controlling the heat (if you have the manual hvac cables). Basically the cable pops out of a mount so the control feels like it has normal resistance, but doesn't actually move any of the doors/controls so there is little or no coolant making it to the heater core. The usual suspect is on the right side footwell. To get at it, remove the rt side dash cover - the underside bit, and glovebox door, remove a piece of plastic ductwork and you can see where the cable attaches to the side of the heater box. If it's come adrift the fix is a very short #8 screw.

here is a link

Thanks for all your help. I will try and tackle this tomorrow. That link you posted oldtin is very helpful looking.

the dash is very easy to take apart.

as others have said … check the coolant level

with the Suby, the rad. was leaking (not readily noticeable) … the temp gauge wouldn't show you anything was wrong (at least not until it was dry ) but the heater would start blowing cold air long before that

OK. here the "progress" so far. The coolant was a little low. About half way up the expansion tank level. I filled it to the top. went for a drive, no heat. I then checked the Bowden cable. It was intact and the heat selector was moving the arm appropriately. I pulled the plug off the heater control valve. The plug was sending the right info (open when hot, closed when cold). The hoses going through the fire wall were warm, not hot like the main rad hose. I took the heater control valve off. It appeared clean and when hooked up to the electrical plug, it moved back and forth when the heat knob went from hot to cold. I held my garden hose up to one of the hoses going through the fire wall. water flowed out the other hose. Actually hot coolant came out first, then the cold water that was pushing it. (these were the two hoses that were connected to the heat control valve). I then hooked everything back up and attempted to bleed the cooling system. I turned the heater on lifted the front of the car 2 1/2' off the ground and ran it for fifteen minutes. there was still a small stream of bubbles coming from the bleed valve after fifteen minutes of idling. the hoses going through the firewall were cold and there is still no heat.

Should I just keep letting it idle with the bleed valve open?

Do I need to keep filling the tank when it gets low while I'm trying to bleed the air?

How long should this take?

Any more suggestions?

there will be those that'll post here with much more experience and knowledge that I have … that said … yes, it can take a long time .. sometimes… and yes I'd make sure the tank stayed full

fixed. I started revving the engine and lots of air and coolant came out the bleed hole. Now I have heat. Filled the rad tank up and good to go. Thanks everyone for their help.