Coolant hoses to heater core: which where?

[Slaloms]

Hey everybody, I'm hoping somebody can help me out here.  Despite looking through both Bentley's (E30/E36) and the BMW TIS CD, I can't seem to find which coolant goes to which heater core inlet.  There's a coolant line from the head and one from the plastic pipe attached to the block that are supposed to go to the heater core.  Which one goes where or does it not even matter?  

I've tried both configurations but haven't been able to get good flow through the core (one hose is hot and not the other).  I think there's still a lot of air trapped in the system as I had drained everything while installing a different M42.  I'm also getting an annoying leak from the "additional thermostat" that was part of the heater core recall, and plan to just eliminate it from the system.  I was really careful to reinstall that in the proper configuration, but that could be related to my flow issue as well.  I feel that as long as I don't let the car overheat, the pressure shouldn't get too high in core.

So head hose to top core line, or bottom?

TIA,

Brian

[Febi Guibo]

going to the heating system:

top = outlet (this goes from the plastic pipe)
bottom = inlet (this goes from the head)

post engine install... I had to bleed my cooling system like... 6 times (sad, I know);

while yer in there, I would replace that heater core thermostat

[Slaloms]

Thanks!  

Yeah, there seems to be a LOT of air trapped in the system.

[individualist]

I went thru a similar issue yesterday on my 91 318is, inadequate flow thru the heater core. Turns out that the valve on the bottom hose that feeds the core was plugged at the pilot port, (hose T'd off from discharge side of core connects to pilot port) I'm not sure if this port operates the valve via pressure or temperature but I do know if it's plugged nothing is going to get thru the main part of the valve. I didn't have a replacement and didn't want to clean it (badly corroded) so I picked up some 3/4" barbed fittings and bypassed it for now. There's more cabin heat than I can stand, now I'm ready for winter.

[Alpine003]

I went thru a similar issue yesterday on my 91 318is, inadequate flow thru the heater core. Turns out that the valve on the bottom hose that feeds the core was plugged at the pilot port, (hose T'd off from discharge side of core connects to pilot port) I'm not sure if this port operates the valve via pressure or temperature but I do know if it's plugged nothing is going to get thru the main part of the valve. I didn't have a replacement and didn't want to clean it (badly corroded) so I picked up some 3/4" barbed fittings and bypassed it for now. There's more cabin heat than I can stand, now I'm ready for winter.

I might have to try bypassing my temperature valve too as I've noticed recenlty that my heater doesn't seem to blow very hot in the recent cold temps. As I understand this valve is more a safety thing than anything else?

One other note about the heater pipes at the bulkhead/firewall.
There is a BMW service bulletin that changes the configuration of the coolant flow. It's a saftey issue so the bulletin does not expire. Meaning they will do it under warranty...as in no cost to you. You can call your dealer and give them your complete vin number, then they can tell you if it has been done. The idea of this change is to keep coolant from flowing onto your feet in the event of a core failure. It includes a valve that shuts flow off to the core if it senses a sudden loss of pressure. I had mine done, it gives the car new heater hoses and fresh coolant.

I'm not sure if this is true or if it applies to all models but worth a shot to ask your dealer.

[FL318is]

Whats a heater?

[Alpine003]

Whats a heater?

Haha. It's the litte red zone on your dial that you rarely set to. I like to show you some white powdery substance that also numbs your tongue and melts in your mouth, but this one is cold, not like the Florida stuff.

[FL318is]

That 'splains it! :cool:

[achtungE30]

so is it just a matter of pulling out that lower hose and the valve is there?