I got no interior heat?

[Swede]

Even when the egine is hot i cant get hot air in the car,its warm but its not as warm as it should be!any ideas?i really hasnt found any leaks but il check it again!

[project86]

Heater core no worky. Maybe

[UofOm3]

thermostat possibly

[project86]

Thermostat would cause the engine to heat up. If the engine is running hot and there is no heat coming into the car then it could be the thermostat.

[AlpineRunner]

Is there a valve that controlls whether coolant flows through the heater core? I don't know how that works but it seems a likely culprit.

[UNHCLL]

Originally posted by AlpineRunner
Is there a valve that controlls whether coolant flows through the heater core? I don't know how that works but it seems a likely culprit.

Yes. Electronically actuated "ball valve" I think. Located inside the cabin, drivers footwell, near the firewall.

[ColinM]

A very common mistake is switching the hoses that go into the heater core. The heater core pipes emerge from the driver's side firewall. The top hose is the coolant return hose.

[jimmyC]

1) Coolant Level (2) Loose belt causing poor circulation (3) restriction in the heater core circuit
4) Air flow problem thru the heater housing
With the engine fully warmed up, and the heater control lever on full hot, rev the engine to 15 - 1800 RPM and check the temperature of the two hoses going into the firewall (next to the brake booster). They should both be VERY hot, like you can only comfortably touch them with your fingertips for 2 - 3 seconds. If this is the case, I would check your that your temp door in the heater box is opening fully when you adjust the temp switch to fully warm.
If both hoses are only warm like you can keep your hand comfortably on them for 10 seconds or longer, I would suspect low coolant level or a loose belt.
If the top hose is significantly warmer than the bottom hose, i would check your heater on/off valve to make sure it is opening. Also possible would be a restricted heater core, but I've rarely seen this on a BMW.
If the bottom hose is hotter than the top one, I would say your hoses are backwards.

[jimmyC]

Colin, I thought the bottom was the return hose

[jimmyC]

Yes, well, in my previous post there, please reverse the words 'top' and 'bottom' in the last two sentences.

[ColinM]

I'm pretty sure the top hose is the return hose. THe valve controls the return flow.

[Swede]

Thanks boys il try and check your ideas in the spring when the car is ready for the streets.

[hardtailer]

Originally posted by UofOm3
thermostat possibly

Originally posted by project86
Thermostat would cause the engine to heat up. If the engine is running hot and there is no heat coming into the car then it could be the thermostat.

It’s not the thermostat.
The thermostat can fail in 2 different ways:

1. Stay open all the time: your engine won’t reach proper operating temps in cold weather (and outer city driving) and your heater won’t work properly either. In fact, you might see a further reduction of coolant temp.
2. Stay closed all the time: your engine will overheat and you will have a working heater. Turning the heater on full blast will actually help cooling down the engine

And then it can fail somewhere in between, i.e. half open.

Coolant flow is like this:
from the water pump the water flows into the ‘3 arm hose’ that’s connected to the thermostat and to the pipe that is connected to the heater core. So wether or not the thermostat is open, coolant will always flow to the heater core. The only way to prevent flow through the heater core itself is the valve that is controlled by the temp knob inside the cabin. As long that’s turned to fully cold, there’s no flow through the heater core.

[powerslide91730]

Hate to be that guy but i dont wanna start a new post.

My heat doesnt work, the hose on the top going into my firewall gets hot but the bottom one is ice cold. had my console out, you think its the valve?

Is the top hose the feed or return, the posts before were confusing, the valve is on the top hose.i think the top is the feed if its the one getting hot, no?

and is there anyway to fix the valve instead of payin 150 for a new one. thanks.

[Sin3]

I just had the same problem and replaced the valve and the core. Its not a hard job at all. If I had to put money on it I would say it is the valve.


As far as fixing the old one I read that some people have done it with some success. I was not in the position to try and fix mine so I just replaced everything. Now the heat works great!