E36 Coolant Level going down after Air Conditioning on

[StephenMark 0]

Hi, my first post here.

I have a 1994 BMW 320i, had it for about 8 months now. Recently had the radiator, thermostat and water pump replaced after a small leak detected in side tank resulting in a water stop in the system, and temperature creeping up.

Last weekend had the air conditioning on warm most of the day to de-mist the front window - the weatehr was horrible. Got home at end of day and the OBC lit up with Check Coolant Level - which had gone down to just below the sensor in the side tank, so filled it up.

Done quite a few kms since then, with no loss in coolant level. Now, the air con doesn't work on cold at all - there's only slightly warm air at the cold setting. When you turn the air con on, it certainly sounds like the compressor (?) kicks in and the fans are all going.

Could having the air con on, which looks like it needs regassing, have affected the system resulting in the coolant level going down? How would it do that? Is it possibly more than just needing the air con regassing I wonder?

Cheers for any help or advice, Stephen.

[hotwire 352]

Hi, firstly - welcome.

No the air con has nothing to do with coolant.

I wonder though, from your description - maybe there was an airlock in the heater core that cleared once you operated the demister. This explaining the drop in coolant level then & not since.

[joshnz 2]

Exactly the same problem I have had the last couple of weeks with the hot weather.

Very weird and probably a bitch to fix.

[*Glenn* 854]

The heater tap may also be jammed in the open position

[StephenMark 0]

I should of mentioned that I havent touched the air con since topping up the coolant - which has remained level since.

[hotwire 352]

I should of mentioned that I havent touched the air con since topping up the coolant - which has remained level since.

As I said - Air con has nothing to do with coolant. The heater does though - hense mine & Glenn's suggestions

[camera doctor 25]

The heater tap may also be jammed in the open position

I had that in my E39 , the heater tap was jammed on Hot, so AC had no effect - could that be what you are experiencing ?

If you set heater to cold on a cold day ( with the car warmed up ) you should not get warmed air - if you do the heater tap / valve may be jammed open as Glen said.

[StephenMark 0]

Hey thanks for all the help,

Not being mechanically minded at all (at least I know where the engine is!!!).

So, if the heater tap tap / valve is jammed/open, does that mean that coolant is actually leaking through that! So, as long as the heater and/or demister, etc is turned off, there shouldn't be a loss?

As camera doctor mentioned - if I set air con to cold I only get warm air. I thought that it might be a re-gas, but maybe I will get the car into Page and get the heater tap/valve looked at? And yeah hotwire, I was using the heat functions - demister on warm - so not the cold air con!!

The new radiator, thermostat and water pump was put in only a month ago. Would a standard pressure test they did also involve turning on the air con / heater, etc to see if this problem was occuring? I know the air con knobs were turned around to the hottest level when I got the car back, and they were previously on the cold blue line when I bought it in. Would checking the heater tap/valve be part of fittings all the new coolant system in?

Thanks for all the support

Cheers all.

[Docile 64]

the heater tap is located on the left side of the car behind the fuse box and engine. your a/c was on heater mode when you came back because that it how you bleed the system. it opens up all the passages in the cooling system flushing out air bubbles and ensuring the right level of coolant is in the system.

i replaced mine and cost me 75 bucks for the part + 5 bucks for new clamps