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PirateZHP
10-07-2013, 09:49 AM
Hey everyone... When I first bought my ZHP, the coolant light would come on and off. After checking the coolant levels, and seeing everything was fine, I asked a few people who said the light(s) in older BMWs sometimes go on and off for no reason. Okay, no big deal then... Well, then it went away and was gone for a few weeks. I checked the level again to make sure it was using some sort of sick reverse psych on me (joke, of course), and everything was fine. Well, today is a rainy day here in Raleigh, NC... so I turned my A/C on. A couple minutes later, the coolant light comes on. I then realized that i haven't had my A/C on in a couple of weeks and that something must be triggering the light when the A/C is on. Any thoughts?

TLDR: The coolant level light comes on when the A/C is on: any idea why?
danewilson77
10-07-2013, 10:42 AM
Most likely you're pushing an Air Bubble around in the system, and/or you have a small leak.

Recommend bleed.

Sent from my S4 > Mason, OH now Free ('http://tapatalk.com/m?id=10')
PirateZHP
10-07-2013, 11:57 AM
Most likely you're pushing an Air Bubble around in the system, and/or you have a small leak.

Recommend bleed.

Sent from my S4 > Mason, OH now Free ('http://tapatalk.com/m?id=10')

And... how difficult is this? Something I should attempt?
danewilson77
10-07-2013, 12:11 PM
Simple.

Raise front end of car.
Start car.
Set heater to 91°, fan in low.
Remove cap slowly.
Open bleed screw.
Add coolant until full, and don't overfill.
Shut bleed valve and install cap.

Someone can maybe point you to official procedure, but I should be close.

Sent from my S4 > Mason, OH now Free ('http://tapatalk.com/m?id=10')
PirateZHP
10-07-2013, 12:15 PM
Sounds easy enough... I will see if I can work on that this weekend. Also, did you see the pics I put on my project thread about the front end links, Dane? You were asking about the removable ball joints, so I provided pics.
kayger12
10-07-2013, 02:30 PM
I'd replace the coolant level sensor.

With the coolant system being the Achilles heal of these cars, I'd want to know that my sensor is functioning properly...
PirateZHP
10-07-2013, 03:57 PM
Thanks. Is that something I should attempt myself as well?
danewilson77
10-07-2013, 04:26 PM
Thanks. Is that something I should attempt myself as well?

Yes. It's in the bottom of the exp tank. Simple.

Sent from my S4 > Mason, OH now Free ('http://tapatalk.com/m?id=10')
PirateZHP
10-08-2013, 04:48 AM
Sweet. I will see if we can get it done in the next week!
alexandre
10-08-2013, 08:40 AM
Very most likely an air bubble.

The AC blows hot air when the wipers are on, no matter what, so it opened the heater core and the air bubble moved around.

So the light is actually gonna show up when you use heat (with or without AC)
kayger12
10-08-2013, 08:47 AM
I don't see how an air bubble could trigger a low coolant light.

Am I missing something?

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danewilson77
10-08-2013, 05:41 PM
If the low level sensor is a resistance type element, the reading will change if air flows past it. By design, it most Lilley won't just clear right away. Not sure though. That was my thinking anyway.

Sent from my S4 > Mason, OH now Free ('http://tapatalk.com/m?id=10')
kayger12
10-09-2013, 01:43 AM
Gotcha. I thought that rubber sheath that sits around the sensor probe would preclude an air bubble affecting it.

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PirateZHP
10-10-2013, 06:14 AM
So far Dane has been correct. I turned the heat on this morning and there it was... the coolant light came on again. So, this weekend, with a friend's help, we will do what Dane suggested and see if that helps!
danewilson77
10-10-2013, 11:59 AM
So far Dane has been correct. I turned the heat on this morning and there it was... the coolant light came on again. So, this weekend, with a friend's help, we will do what Dane suggested and see if that helps!

Fingers crossed.

Could be as KG said or could be a small leak that is thermally affected as well.

Sent from my S4 > Mason, OH now Free ('http://tapatalk.com/m?id=10')
JDDsZHP
10-11-2013, 08:22 PM
I am dealing with the exact same issue. The light also seems associated with the heater core.

I first replaced the expansion tank cap, as suggested by Bruce. I will be trying the bleed this weekend as well. If anyone has a quick link to a good tutorial, I would be thankful for saving me some Google time.

I will update results for reference.
kayger12
10-12-2013, 03:11 AM
I am dealing with the exact same issue. The light also seems associated with the heater core.

I first replaced the expansion tank cap, as suggested by Bruce. I will be trying the bleed this weekend as well. If anyone has a quick link to a good tutorial, I would be thankful for saving me some Google time.

I will update results for reference.

http://www.bmw330ci.net/maintenance/coolant.php

Follow steps 1 through 4 and then skip to step 15.

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