Bleeding coolant after motor install, can't get any heat

[SmokeE30]

Just put an 89m20b25 in a 92 325ic all went pretty smooth except bleeding the cooling system resulted in the temp going up to near 3/4 mark once before falling back down to just before half way and staying there but no heat would come from the vents. I had the heat set to Max but I don't think coolant Is getting circulated through the heater core.

The 92 had the later recall valve at the firewall so I left it there but now I'm thinking maybe it's the issue, I've never delt with these valves before but my understanding is that it could prevent flow to the heater core if it has failed. Anybody had a similar experience?

After work I'm gonna drive the car around a bit and see how it goes but looking for ideas if that doesnt do it.

[vpilarrt]

You sure you don't have the heater lines switched (in to out and visaversa)?

[SmokeE30]

Not 100% sure since I did move hoses around but shouldn't coolant still flow through the core regardless?

[jlevie]

If the hoses are swapped, there will be no flow through the heater core.

[SmokeE30]

Currently I have the spider hose connected to the top and the valve Off the back of the head to the bottom is this correct some searching around has me confused As to which way it goes

[SmokeE30]

Ok well my routing matches both the early and late model cars I have here so I guess that's correct. The bottom hose coming from the back of the head is hot but the spider hose is not hot, from the thermostat housing to the firewall it's cool. Ideas?

[jlevie]

This could be a problem with the heater core valve or it's control circuit. The valve is power on to close so disconnecting it will open the valve. The valve has flow direction marked on it and the flow is from the rear of the head to the thermostat housing. So it isn't difficult to check the hose orientation.

[SmokeE30]

I will try unplugging the valve after work as I will be bleeding the car again after work due to the top radiator hose springing a leak

[SmokeE30]

Ok well after replacing a hose and refilling with coolant and bleeding the car acted same as before. No heat, temp gauge stays just below half way, bottom heater core hose hot but the top hose cold.

Decide to try unplugging heater control valve, I get to it and see the valve is located on the top hose feed before the heater core, so I unplug the electrical connector and run the car again. Same as before I can feel the metal feed pipe to the heater core is hot. As is the plastic where it enters, but the top line and the plastic near it is still cold.

At this point I'm pretty sure the heater core is clogged. I mean is there any other explanation? I talked to the cars owner and he stated that the heat did work before but always took a while before it got warm so I'm thinking it has been failing for a while.

One thing that confuses me though is why did BMW put the valve on the top return line to trap all the hot coolant in the heater core? Shouldn't it be the other way around to keep the hot coolant out untill needed?

[SmokeE30]

Well finaly got the old heater core out and wouldn't ya know it wasn't clogged I flushed out some very brown coolant but it flowed right through.

The water valve however did not flow, it was failed in the closed position not allowing coolant to exit the heater core. I'm not sure why the heater core wouldn't still get hot and thus alow for heat but it deffinetly is stuck closed so I'm replacing it with a good used part as you can not buy them new at the moment.