Uneven heat?

[roccaas]

'87 M6...

Heater blows very hot when the car first gets to operating temperature. Then it begins to alternate between very hot and lukewarm even though the engine temp gauge is very settled at 1/3 of the way up from cold.

I'd guess the heater core needs to be flushed (as in any car with hot water heat). Is there a thermostat on the heater circuit?

Any other ideas??


Thanks!

[sixseries]

how do you flush a heater core? and could this be the problem that my car has when the heat will sometimes work when the car is fully warmed up and sometimes it will blow out cool air

[CW6er]

The failure mode of the heater valve (when it loses power) is to fail full open, so if it is varying between very hot and lukewarm it seems the valve is working.

Check that the small white nylon vacuum line is connected to the intake plenum in the engine bay and to the interior temperature sensor clipped to the drivers kick panel inside. The vacuum draws a small amount of air through the interior sensor to help keep the temp constant (fig. 4 below).

There is also a heater core temp sensor (Fig. 6 below) that can be tested with an ohmmeter, do you have a Bentley manual?

http://www.stormpages.com/countchocula1/bmw/bmwetm157.jpg
http://www.stormpages.com/countchocula1/bmw/bmwetm213.jpg

[CW6er]

Check out this article on the heater valve core, scroll down to it:

http://bigcoupe.com/phpBB2/viewtopic.php?t=2418

[Alex E24 E30]

Interesting point on the interior temp sensor. Mine has nothing on the kick panel to attach to. Since it's still open (been meaning to plug it), could it be the cause of my car ALWAYS blowing hot air? No matter what I do, it always wafts out hot air to the top and bottom vents.

[CW6er]

Interesting point on the interior temp sensor. Mine has nothing on the kick panel to attach to. Since it's still open (been meaning to plug it), could it be the cause of my car ALWAYS blowing hot air? No matter what I do, it always wafts out hot air to the top and bottom vents.

There is a plastic grill that snaps into the fiberboard kickpanel and then the sensor snaps into the grill from behind. I have found that if the grill is missing, you can line up the ears of the sensor and twist it into the opening in the kickpanel.

If the heat is on all of the time, this usually means the heater valve has failed. Go through the article in the link above and check the heater valve.

[bimmerjo]

I know, I'm posting in an old dead thread, but at least it shows i'm searching! :)

Okay, I have a crumbled up interior temp sensor. And I'm wondering how in the world do I find another?? brand new these are 200 from both pelican and bavauto, and ebay has squat... Any suggestions on locating one of these? Last one I bid on in ebay was 12 bucks and lost do to the fact that I couldn't get to it in time to place a higher bid.

Any help would be greatly appreciated :)

[smaglik]

you are on teh right track with used. hopefully someone here has one. back in the haygood days, i purchased a used one from him for 40something.

[86GT635]

We're about to start up a swap-meet thread like we had last fall. Somebody should have one of them for sale. Actually I do. 20 shipped sounds good?

[bimmerjo]

Think you can hold on to it for about a week and a half? I just bought three U-Joints for her so I can rebuild my driveshaft. But the price is just fine.

[86GT635]

no biggie. take your time. get back to me when you want it! if money is tight I am flexible as I am not using this piece. i just threw that price out there because of umm what smaglik paid and then for the new one.
-DJ

[bimmerjo]

no biggie. take your time. get back to me when you want it! if money is tight I am flexible as I am not using this piece. i just threw that price out there because of umm what smaglik paid and then for the new one.
-DJ

Hey, still have it? I can buy it now :)