ok, I am going to attempt to describe what is happening with my car.
I am losing coolant somewhere, it is not dripping anywhere I can see.
I am smelling coolant in the cabin of the car ONLY when I use the heater, and of course all the windows fog up pretty bad.
BUT, I do not consistently smell coolant in the cabin when I use the heater, only on the REALLY cold days do I have the problem. For instance today, maybe 38 degrees F, and I used the heater and only smelt a tiny bit of coolant, and the windows did not fog up.
Now it seems to me that everything is pointing to a leaky heater core. BUT, why would I only experience the problem on really cold days?
Also, I went about 2 weeks without using the heater, since it becomes impossible to drive with the foggy windows. During this 2 weeks I still was losing coolant.
IF I had a leaky heater core, and I for 2 weeks was not using my heater, why would I be losing coolant?
Is it possible that I don't have a leaky heater core and something else could be wrong?
I hope that it could be something else, because I don't have the time to repair it myself, nor do I have the money to pay someone else !!!!
soo hard to say, at first i though yes heatercore (and if you wanna know heatercore replacement is one of the most expensive repairs on our cars) however i cannot be certain therefore please be sure to check with a professional in your area.
i had to replace my heater core in my 300zx. i know its not a bmw but it might have the same concept. well in my case the coolant was leaking inside the dash and causing a little puddle beneath the accelerator pedal. and it would start to leak every time the engine got fairly warm, with the heater on or not. but to take it out and replace, i had to take the entire dash off, steering wheel, and the heater system apart. so it was time consuming. but i don't know how difficult it would be to replace on an e36. but you'll save money if you do it yourself.
Again, from what your saying the leak is continuous...but I think it is possible that the leak gets worse when the heat is on...maybe having something to do with the path of the coolant in the system when the heat is turned on....
the misteriosly loss of coolant is due to a leaky heater core.
the explanation of foggy and coolant smell clearly indicates this problem.
because the heater core is put in the same box as the ac evaporator, when the coolant leakes it ends up being drained on the ac drain.. this drain goes out on the bottom of the car on top of the transmission.
and is problaly leaking so lottle you did not notice. also cooling can only flow to the heater core when the heater valve is open, so if the coolant was leaking even when not using the heating, the valve is stuck in the open position. that is ahy when doing coolant fluhss, you have to have the heating on, so you can take all the air out of the system, including the air that goes into the heater core.
if its not the heater core, it the o ring that are between the pipes from the engine compartment to the heater core, they fail too.
but in most cases it is the core that goes bad.
the reson why you only have fog on very cold days is because you need a lot of temperature difference form outside to inside in order to create moisture, which is what fog and all about.
it is horrable to do this job, removal of dashboard will be necessary.
but if you have a garage and nothing to do on the weekend is not a bad project..
so in case you decide to do it, i also recommend you to clean all electrical contacts underneath the dashboard, this fixes most of the electrical problems that como and go. because of age and air mouisture some rust builds up on the electrical contacts and the electrical system goes cahoots.
hope this helps.
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