Heater core?

Ever since I've had my iX, the heater has acted a bit oddly. When the temperature control is turned all the way up, it blows nice and hot. In fact, even in the middle of winter in the frozen north, it's often too hot, and I want to turn it down. The problem is that if I back off the temperature know just a few degrees below full, it gets way too cold. The progression is very non-linear -- there's a big step, and it happens right near full warm.

Possibly related to this is that in order to get warm air out of the vents, the blower fan needs to be on 2 or higher. If I turn the fan down to 1, the air goes cold.

Is this a sign of my heater core needing replacing? If so, how horrendous a job is that?

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Dave
'91 325iX

It sounds more like the electronic valve needs replacing. If the core was plugged, it wouldn't be blowing hot at any time.
Replacing the valve should be a relatively simple job. Once the center console has been removed, you have complete access to the valve.

Hi Dave
I will be watching this one with interest, my heater does exactly the same, if I turn it all the way up, it heats the car up like nobody's business, but just turn it about a quarter back and it is ice cold again, either one or the other, very no progession.
Mine has the aircon so the heater box and valve are situated low down almost on the floor od the transmision tunnel, so as Pete said, once the center console is out, it is not too bad to get to. Apparently the cars without aircon are harder, as the heater core sits a lot higher under the dash.

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E30'S AREN'T BUILT, THEY'RE CAUGHT IN THE WILD!!!



When in doubt, use full throttle,
it may not improve the situation, but it will end the suspence.

Thanks, Peter. I'll give that a look sometime. (Not real soon since I'm not real excited about taking apart the dash in an unheated garage. )

Is the heater valve you're talking about the one that looks like this?


i.e part #7 in this diagram?


__________
Dave
'91 325iX

Quote
Dave_G
Thanks, Peter. I'll give that a look sometime. (Not real soon since I'm not real excited about taking apart the dash in an unheated garage. )

Is the heater valve you're talking about the one that looks like this?


i.e part #7 in this diagram?

That looks like it Dave, I think there are two different kinds; one has a plastic top or hose and one has a metal one. It's been awhile but there is some difference in there, maybe it relates to the heater core itself but be careful and ask questions.

I agree with peter about the heater valve being at fault, it's a common problem with these electrical things.... Rick

I will also be watching this one with interest, as mine also has the same behavior. Though I suppose if mine goes the way of a track car, full blast hot or cold is about what I'll want

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1989 - E30 - M20 - Manual. Approximately 270,000 miles
2000 - E46 - M52TUB28 - Manual. Approximately 110,000 miles

I'm resurrecting this one from hibernation for a report and another question.

Now that winter is coming again, I just finally replaced the heater valve. It wasn't too bad except for one of the five screws being almost inaccessible and requiring me to do the oh-so comical standing-on-my-head-under-the-dash dance, accompanied by considerable swearing. Now that I know how all the pieces fit together, it'll probably be easier if I ever need to do it again.

But still all is not well. After refilling the coolant, getting the car up to normal temperature, bleeding out the air bubbles, turning on the heater and checking my work for leaks, there is now NO warm air coming out of the heater at all. Before I replaced the valve, I at least had hot air, I just couldn't control it very well. Now I've got nothing.

The heater valve itself seems to be working (it should, it's new), as I can hear it click when I adjust the temperature. It's also clicking in the right place (a few degrees above full cold), so it seems to be adjusted correctly. The only thing left I can think of is the heater core. The lower heater hose going into the heater core is fairly hot, and the one coming out is completely cold. This seems to support the heater core being plugged. But why would it suddenly become plugged at the exact time that I replaced the heater valve? Maybe it was marginal to begin with, and flushing and refilling the coolant sent junk into the core, clogging what was left open? But the fact that the heater was so hot before I began the work doesn't seem to support the idea of a mostly-clogged heater core.

I'm kind of at a loss. Before I go out and spend $200 on a new heater core, does anyone have any ideas?

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Dave
'91 325iX

try reversing the hoses to see if any blockage might be cleared.

I agree, if it was hot before then it still should be.

Perhaps it has an airlock...

Quote
Archeo-peteriX
Perhaps it has an airlock...

Peter, you're a genius. That's exactly what it was. I was quite thorough in bleeding the system after filling it, but it was not enough to get the air I had introduced to the system way down by the heater core. Taking inspiration from a hint I found elsewhere on the Internet, I raised the front of the car up on ramps, and after running the engine some more, that was enough to get the air bubble out of the system. I've got heat!

__________
Dave
'91 325iX

Quote
Dave_G

Quote
Archeo-peteriX
Perhaps it has an airlock...

Peter, you're a genius. That's exactly what it was. I was quite thorough in bleeding the system after filling it, but it was not enough to get the air I had introduced to the system way down by the heater core. Taking inspiration from a hint I found elsewhere on the Internet, I raised the front of the car up on ramps, and after running the engine some more, that was enough to get the air bubble out of the system. I've got heat!

Congrats!
I'm always happy when something actually works

No genius here...I had to learn that one by experience



Edited 1 time(s). Last edit at 10/15/2011 05:28PM by Archeo-peteriX.

Interesting. Our heater hasn't worked for a long long time. My son is griping about the cold. I assumed that the valve or something else has died. Now I'm wondering if I have this airlock.. BUT it's been a couple of years since it quit working. Could it have this airlock for that long?

Not likely, the changes in pressure from hot to cold would evenually cause the air to be dissolved in the water. It may be the valve..

Bob in Lake Havasu

Yeah, I think Bob is probably right. After that long, whatever is plugging up the line probably isn't air. My guesses would be the heater valve or heater core as likely candidates. On the other hand, if you're gonna have a car without a heater, at least you're living in the right location.

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Dave
'91 325iX

True.. we are definitely in a temperate climate but it does get into the 30's for a good portion of winter where I live.

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sdp
True.. we are definitely in a temperate climate but it does get into the 30's for a good portion of winter where I live.

When the car is hot and the heater is on full blast check the in and out hose on the firewall that lead in to the heater; one should be hot (ideally both but...), if that's so you have a blockage at the valve/core and if don't get any heat it's usually the valve. If both hoses are cold you have other problems... phone home

Rick