Heat at speed, cool air at idle

Severian · 12-02-2005, 02:04 PM

Hello again everyone, I endeavored to fix the heat in my car last night, and it worked! See this thread 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** · 12-02-2005, 02:20 PM

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

Severian · 12-02-2005, 02:40 PM

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** · 12-02-2005, 02:58 PM

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 · 12-02-2005, 03:04 PM

Thanks Cali, I found the precise diagram for this part (it's item 5, but you knew that), 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** · 12-02-2005, 03:06 PM

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 · 12-02-2005, 03:22 PM

****! 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 · 12-02-2005, 04:16 PM

Quote:

Originally Posted by 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

LOL ... i'm so good, i answer questions when i'm not even on!

cali-ti = eric, 1996 328ti = steven

aceyx · 12-02-2005, 09:08 PM

Quote:

Originally Posted by 1996 328ti

And STOP calling me Cali.

At least he didn't call you Shirley.

**1996 328ti** · 12-03-2005, 02:20 AM

Quote:

Originally Posted by Severian

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 · 02-16-2006, 01:33 PM

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 · 02-21-2008, 02:18 PM

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...02&hg=64&fg=18

teetime4one · 02-21-2008, 02:35 PM

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 · 02-21-2008, 03:04 PM

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 · 02-21-2008, 03:12 PM

good luck

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