Anti Freeze loss??

[taralst]

My '95 540i(m60) has BMW anti freeze(proper level), new hoses,new radiator all since June 2005. No problems whatsoever, temperature gauge exactly at 12 o'clock, no loss of anti-freeze.(heater controls are off, both sides)
Now that it is getting colder, in the morning I turn the heater controls to on(all the way clockwise, both sides) and the car heats up perfectly inside the cabin and the gauge is still 12 o'clock. As the day warms up, I turn the heater controls off(all the way counter-clockwise)
The temperature gauge is still at 12 o'clock, still no problem.
After I get home from work (approx 20 min drive), car is parked. After a couple of hours parked, I go to take kids to soccer pratice and I have appox 1.5 quart of antifreeze on the driveway.
(This has happened 2 times, once coming home from work and once on a Saturday, running errands)
The coolant level all summer was at the proper level(when cold, anti-freeze was on the 'cold line). No loss of anti-freeze during the summer.

If I don't use the heater controls, no loss of anti-freeze.

If I use the heater controls, turn them on for awhile and then later as the day warms up , turn them off, I have had a loss of anti-freeze.(not every time though)
Is there air still trapped inside the heater core causing this??
Any help greatly appreciated.
Tim

[632 Regal]

strange animal, is there signs of leakage along the firewall in the vacinity of the heater valves?

Another thing you should do is check the hose clamps, they were all done a while ago and might need to be tightened a final time after the rubber had time to relax.

[uscharalph]

Or Heater Core.

[taralst]

strange animal, is there signs of leakage along the firewall in the vacinity of the heater valves?

Another thing you should do is check the hose clamps, they were all done a while ago and might need to be tightened a final time after the rubber had time to relax.

Thanks for your response: There are no leaks at the heater valves along the firewall. The heater core is also not leaking.

The anti-freeze loss is coming from the overflow tube on the expansion tank.
Can't figure this one out. No leaks anywhere. Only overflows when operating the temperature control for heat inside cabin.
Tim

[Anthony (M5 in Calgary)]

No idea about the coolant loss, but why turn the temperature knobs to the extremes? That defeates the automatic temperature control.

I've always found the car stays comfortable if the knobs are left at 20C (68F) and never move them more than a degree or two. I use the upper vent temp control at the extremes only in extreme weather, usually leaving it midway.

I'm so spoiled by the temperature control in this car that whenever I get in a car without it I find myself wondering why I'm too hot/cold...

[632 Regal]

Ill bet the car wasnt bled with the heater on full hot.


Thanks for your response: There are no leaks at the heater valves along the firewall. The heater core is also not leaking.

The anti-freeze loss is coming from the overflow tube on the expansion tank.
Can't figure this one out. No leaks anywhere. Only overflows when operating the temperature control for heat inside cabin.
Tim