Heat at speed, cool air at idle

[Severian]

Hello again everyone, I endeavored to fix the heat in my car last night, and it worked! See this thread (http://www.318ti.org/forum/showthread.php?t=2273) for details if you want. But now that the Bowden cable properly operates the heater flap (so it shouldn't cause any problems), I notice that even though the car is up to temp the air is cool at idle. Only when I hit the revs does the heat kick in. So, hot air at speed, cool air at idle.

Any ideas? This was unexpected. It may be unrelated, but I noticed that I couldn't burp my cooling system without revving the engine last night, either.

Thanks in advance guys.

[1996 328ti]

Could also be the heater bypass valve located on the firewall.

[Severian]

When you say "on the firewall" does that mean under the hood up against the wall between the engine and the cab? Or do you mean inside the cab up against the wall in between the engine and the cab? Thanks cali.

I found a heater valve for $74.95 at bavauto.com, but is this something I could replace on my own? Do those hoses all have antifreeze in them?

[1996 328ti]

It is on the engine side. Don't replace it unless it's bad.
Turn on your heat and be sure the engine is at operating temperture.
I think there are two hoses going to the valve. Both hoses should be warm.

Those hoses would have antifreeze in them. Then the system would need to be bleed again for air. I've never done it, just watched a mechanic do it.

[Severian]

Thanks Cali, I found the precise diagram for this part (it's item 5, but you knew that (http://www.realoem.com/bmw/showparts.do?model=CG73&mospid=47506&btnr=64_0202&hg=64&fg=18)), and I see where it should be in relation to the heater radiator. Now that I'm becoming more comfortable with how these "cars" work I think I can test to see if the two tubes are warm at idle. As you suspect, I suspect they will not be until I rev the engine, and even then the valve will only push hot water for as long as I throttle. But these are only guesses.

To bleed the entire system there's a valve on the bottom of the radiator, no? If I catch all of the coolant/antifreeze, can I reuse it after I perform the operation if I use a clean container to catch the coolant mixture?

[1996 328ti]

There is a bleed valve or screw on the top of the raditor.
You should have water flowing through the valve at idle.
And STOP calling me Cali. ;)

[Severian]

****! SO sorry about that, man. I feel like a jerk for getting you confused with another member.

I know the plastic bleeder screw you're talking about next to the coolant fill cap. Perhaps I can just lift the pump up and out of there (if the tubes are flexible enough) and use a vise to clamp them while I change out the part. Is that what you're thinking?

Thanks 1996 328ti
:)

[cali-ti]

****! SO sorry about that, man. I feel like a jerk for getting you confused with another member.

I know the plastic bleeder screw you're talking about next to the coolant fill cap. Perhaps I can just lift the pump up and out of there (if the tubes are flexible enough) and use a vise to clamp them while I change out the part. Is that what you're thinking?

Thanks 1996 328ti
:)
LOL ... i'm so good, i answer questions when i'm not even on! :biggrin:

cali-ti = eric, 1996 328ti = steven :)

[aceyx]

And STOP calling me Cali. ;)

At least he didn't call you Shirley. :biggrin:

[1996 328ti]

I know the plastic bleeder screw you're talking about next to the coolant fill cap. Perhaps I can just lift the pump up and out of there (if the tubes are flexible enough) and use a vise to clamp them while I change out the part. Is that what you're thinking?It's not difficult to open the bleed screw. But be sure it's a bad valve first. Don't change perfectly working parts for another perfectly working part.

[Severian]

An update (and solution) to our quirky problem; a new Water Pump.

Recently our engine started making a slightly alarming metal-on-metal style noise...it was running louder than it should have. Our mechanic said the water pump was on the verge of going bad, and it was making the loud noise. With the new water pump we have heat all the time (even at idle).

WoOt!

[Severian]

Update: We no longer have hot air at idle. On days when it's really cold I just turn off the blower since it starts blowing cold air. I'm going to have a new Water Valve put in.
http://www.realoem.com/bmw/showparts.do?model=CG73&mospid=47506&btnr=64_0202&hg=64&fg=18

[teetime4one]

so, your car worked fine for the past 2 years with the new water pump...then the heat went out recently?
i also have a problem like this...the heat problem i mean.
post again if the water valve works for ya.
thanks

[Severian]

I will indeed. The problem is not an overnight development...I've been dealing with it by revving the engine at stop lights. I am tired of this though, and I would like my car to blow hot air while at idle RPMs. My wife would also like it; she's ready to disown the car. Such animosity towards a car into which I've poured so much work cannot go unchecked!

So far I've performed (or had performed) the following on this car:
* Replaced Thermostat
* Burped
* Fixed bowden cable problem
* Replaced water pump

All fixes resulted in improvement of some kind. This is sort of the final frontier for heat issues I think.

[teetime4one]

good luck

[elchicano318ti]

Yea i have the same problem, it just started like to two days ago i'm gonna check it out and see if i can fix it.

[teetime4one]

sounds good Dave.
let me know what you find.

[elchicano318ti]

I gotta go to school in a bit but i 'll check it when i come back.

[elchicano318ti]

Is the heater bypass valve and the heater control valve the same thing? I just checked my car the heater gauge is in the middle and its blowing out warm air. I'm gonna check the coolant it might need some. I checked the hose in the bottom of the radiator it is warm so it might be the bypass valve right? I'm starting to get confused with all this stuff.

[Severian]

Now, after some time has passed, I'm happy to report that I was probably just suffering from a shortage of coolant all along. Once I used the bleeder screw technique and added plenty of coolant I was good to go, the heat works MUCH better than it did before.

Again, this is also when the following things have been done already:

* Replaced Thermostat
* Fixed bowden cable problem
* Replaced water pump

Hey, at least we're warm now! That's what counts.

[elchicano318ti]

Okay since winter is on its way. I need to fix my heater. So where is the bypass valve at. I tried looking for it and i couldn't find it. It's prolly somewhere under my nose but i don't see it. Can someone show me on the pic where i should be looking at.

http://i210.photobucket.com/albums/bb309/elchicano411/engine.jpg

[aceyx]

Wrong side of the firewall. Go in through the passenger side kick panel.

[elchicano318ti]

It is on the engine side. Don't replace it unless it's bad.
Turn on your heat and be sure the engine is at operating temperture.
I think there are two hoses going to the valve. Both hoses should be warm.

Those hoses would have antifreeze in them. Then the system would need to be bleed again for air. I've never done it, just watched a mechanic do it.


hmm i thought it was under the hood since thats what i got from steve's comment. I guess i read it wrong. Well if its true and thats where its at no wonder i couldn't find it. haha:biggrin: Thanks i will look for it then and see if i need to replace mine.

[aceyx]

I may be confusing this with some other part.

[elchicano318ti]

I think you are talking about the heater cable with the yellow tab. I will check that as soon as i check this, i read in another thread where its located and have a general idea of where it's at. So i'll see if i can find it tomorrow.

[RidingSimple]

It's located on the back right of the motor from that angle, near the fusebox. Two heater hoses go from the back of the motor, and in through the firewall to the heater core behind the radio area. I have an extra heater core and switch if anyone needs them (building a track car in Hawaii, don't need heat).

[Mr.Squeelerz]

I'm having the same problem too. What good is my remote start if I only get heat at speeds?....boooo

I'm watching this thread for possible solutions.

[nyle]

hm. generally the lack of heat at idle is because the system has a little bit of air in it.

which is a bitch. there are a bunch of different ways to bleed your coolant (and verify that it is properly bled). search around and try a couple.

I would do this before jumping to the assumption that the heater core valve is broken.

[elchicano318ti]

Well i finally got around to check my heating issue. I check the yellow cable and the PO fixed it by getting it screwed on. I checked the hoses that go to the heater core valve and both of them are hot. I had the car at an incline on my drive way. I bled the radiator and waited until i got the bubbles out. What i noticed is that i was getting hotter air while the car was on my inclined driveway then when i was driving with the heater on. So i'm lost i don't know where to go from here. The radiator and thermostat where changed about two years ago. Any suggestions would be welcomed.