new e36 m3 owner with problem

[ecosse109]

hi there i have been searching this site and i seem to have a problem no one else has and i am needing some help, i have an e36 98 m3 euro

when i start my car up with the heaters on 37 and full blowers i get heat coming out from all vents but only for about 5 minutes, after this i get cold air blowing from all the heaters, the longer i leave or drive the car the air gets colder, i had problems with the hvac unit and final stage resistor on my 318 and it isnt these, it also isnt the hot/cold air switch on the dash

i have bled the radiator 3 times but to no avail, the temp gauge on the dash dosnt go above halfway, i have the seperate expansion tank on the radiator, is it true these are self bleeding or do they have a bleed valve

everyone else seems to be overheating but im not im just getting cold air from everywhere, cant see any leaks on the system and in not loosing any coolant

any ideas on where to start would be much appreciated

thanks

[Manolito]

This is an interesting problem.

First we have to figure out whether the heater valve on the firewall is staying open. After the car has run a while and the air is blowing cold, touch the hoses that go to the heater valve under the hood, one hose should be too hot to touch. If the hoses are both just warm, then the problem is likely the heater valve or the electronics controlling that valve.

The climate control computer in e36s is notoriously prone to failure, but yours is not showing the usual symptoms of failure. I discuss fixing the common problem on my web page:

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