Heater not working

[Rasta]

I have seen posts about this topic but I cannot seem to fix my problem. I am trying to fix the heater on my '91 318is. The heater has not work since I had to do a cooling system repair about 10 years ago. Long story short, the car overheated and burnt head gasket. I fixed it but never installed a thermostat in it. A couple of years after that repair, the heater thermostat, the one by the break pump, broke the top seal and was leaking so I eliminated it. Since then the heater has not worked. I am doing miscelaneous work to the car right now and I installed the front thermostat and also bought a new heater thermostat and installed it. I filled the system with water/coolant and bled it but the heater still doesn't work. The temperature gauge does not rise over a little less than half. Hoses that go to the heater core do not warm up. The system blows cold air. The blower works on all speeds. Can anybody share some wisdom?

[BETTERTECH824]

hey there,

 I have the exact car you have, 1991 BMW 318is .
There is only one thermostat, its behind the part that the radiator hoses attach to
on the front of the motor. You said "the one by the break pump" what on earth
are you talking about there is one only. if you have a thermostat down where you
say remove it . post a pict of it.  cause Id love to see it.

[Bald Eagle]

There was pressure relief valve installed as part of a warranty issue that is attached on the rear heater port of the head. It regulated the flow of coolant to the heater core which prevented the heater core from exploding (which is interesting). Its a mess of hoses and not really needed in most cases. I eliminated mine without issue. You might check to see if your water-pump is dead or double check coolant as the M42 is a PITA to "burp" the air out at times which can prevent coolant flow.  You might also have blockage somewhere.

[colin86325]

I belive the OP is talking about the heater valve, #16:

http://bmwfans.info/parts/catalog/E30/2-doors/USA/318is-M42/browse/heater_and_air_conditioning/heater_radiator_blower/#16

[BETTERTECH824]

i was wrong to say there is only one thermostat.
recently I replumbed my m42 & found that there is
one on the heater hoses.
im very sorry to say there isnt when obviously there is