Heater core bypass

[matt]

Well, sort of, but it doesn't tell the whole story. Connect the end of the red arrow pointing down into the inlet to the radiator.

Coolant circulates through the block, the head, the radiator, then back. Things like the heater and throttle body lines draw coolant from high pressure areas (the block) and return it to a low pressure area (inlet of the pump from the timing cover).

[DREWHALL]

You sure it cuts flow to the heater core? I don't remember seeing a valve on the hoses going into the heater core when I swapped mine. I know some cars use blend doors that control the flow of air over the heater core, instead of actually removing the heater core from the system when you turn it to cold/ambient temp air. I know my Rabbit has a physical valve in the heater core hoses, but the E30 did not when I had everything apart. Could be wrong though I haven't looked at my manual for it.

Edit: After looking at the Bentley, it is a blend system, with a solenoid regulating the coolant flow through the heater core.

[etxxz]

So I don’t see it. I’m mind boggled. I want to simplify my engine bay. Tuck the harness, clean this mess up. My engine is out too so it’s the perfect time.

Suppose I block off the back (heater core) and eliminate the throttle body loop (warm FL climate). I no longer need the spyder hose, just go from the head entrance by cyl 1 to the overflow tank. I can chop the spyder hose and go to the overflow tank, this should be a point of negative pressure so I shouldn’t worry about it blowing out if unsecured…. Or maybe not.

Am I missing something here? If flow can’t go to the back of the head, how does it get to and from the radiator?? …I mean water needs to go somewhere otherwise its gonna create pressure and engine resistance with the T-stat closed = blow things up.

[matt]

BMW thermostats do not open or close. It is a 3 way valve.

[etxxz]

that just confuses me more. Its a wax element that actuates by heat and so it does open in that sense. Can you describe the 3-way function?



Plan:
close the back (flat plate).
close TB outlet @ head (plug)
Chop metal spyder hose and route it to the overflow tank.
Sounds good?

[matt]

Coolant in a BMW is always circulating. Either just through the block and head or through the block, head, and radiator.

Your plan works.

[BigD]

Sorry to kick a dead horse again - I've conceded that I need to plug the hoses to delete the heater. But now I need to route my turbo cooling lines. I plan to pick up the coolant from the TB warming circuit but I was planning to use the return from it as well. If what was said above is correct, then I will be heating the coolant up further and returning it to the block without going to the radiator.

Can someone confirm FOR SURE that the barb on the back of the timing cover leads back into the engine, and not through the thermostat first? I would look for myself but my engine is away being built, maybe I'll stop by and have a look. If that's the case then maybe I should tap the thermostat cover so the drain goes right back into the radiator.

[BigD]

I think I found my answer in a pic of my head I snapped while at the builder's. Looks like any coolant that comes up through the timing cover (ie water pump or heater/overflow hose) goes into the block. The only coolant that goes to the radiator is through that outer passage on the head.