*Back of the head coolant hose question*

[blackhawkimpact]

So is this confirmed? Head goes to valve?
Cuz I had it the way everyone said, "back of head to bottom pipe and spider to top pipe"
Maybe that's why my heater core blew up?

[328ijunkie]

If you hook it up backwards basically youre going to be blowing coolant through the heater valve the wrong direction (which it wasnt designed for). If the valve were to hold up in that case it would basically allow hot coolant that is being forced into the valve to also be pressurizing the heater core so yeah it could def blow it up in addition to the problem of running your AC air through a hot heater core.

[328ijunkie]

Yeah you guys had me second guessing myself for a little there as ive done this this way on a ton of customer cars.

[u3b3rg33k]

...unless the flow is supposed to go into the heater core first, then to the valve, it should go to the bottom. I can't imagine the HC being filled with hot coolant on a summer day, bmw designers wouldn't do that to us would they?

What do you mean by that?

Whether or not the valve is on one side or the other of the heater core, there will be no flow, and thus no hot coolant if the valve is closed.
If the valve only functions with flow going one way, that's another matter entirely, but it doesn't affect the heater core.

[monkeytaco]

I mean that if the flow from the head went to the heater core before it hit the valve the core would always have warm fluid pushing toward it. Even if the valve is not open the coolant within the lines will search for equilibrium and thus the turbulence within the hose itself will warm.

You're correct that there shouldn't be flow at all with the valve closed. Based on a couple more cars I checked out today, it appears the valve is always on the inlet. However I don't know if its a one way valve. Next time I'm at a breaker I'll open up one on a donor car...

[u3b3rg33k]

I mean that if the flow from the head went to the heater core before it hit the valve the core would always have warm fluid pushing toward it. Even if the valve is not open the coolant within the lines will search for equilibrium and thus the turbulence within the hose itself will warm.

You're correct that there shouldn't be flow at all with the valve closed. Based on a couple more cars I checked out today, it appears the valve is always on the inlet. However I don't know if its a one way valve. Next time I'm at a breaker I'll open up one on a donor car...

That may be, but the heater core is downhill, and that effectively creates a heat trap, nullifying the issue. That effect is often sought and utilized near home water heaters, to prevent the water heater from heating a large quantity of pipe while not in use. It is also used for the opposite purpose near industrial dishwashers (by the smarter plumbers) by placing the booster heater down low with as few bends in the plumbing as possible to keep the rinse water hot for sanitary (and $ savings) purposes.

As to the latter, I only mentioned it because of the anecdotal evidence pointing toward the valve disliking flow in the 'wrong' direction.

[328ijunkie]

I have taken a few of these valves apart. They simply have a diaphram that when pushed a little downward is forced shut by the water flowing over it. It wouldnt work really at all in reverse as the diaphram wasnt made to fight flow in the opposite direction.

[samiam3356]

I know a lot of people who would have thought like me and just assumed that it goes to the bottom. Glad you said something in the other thread or I never would have started this one .

[328ijunkie]

Werd~!

[samiam3356]

Pm'd Jlevie as well just to run it by him and he said the back of the hose will ALWAYS go to the valve.

[328ijunkie]

Cool Cool!

[Fidhle007]

Sorry to drag up an old thread but I'm hooking up my coolant lines tonight and I happened to notice there is a flow direction on the heater valve itself and this is OUT of the core. Mine is an '89 325i with the valve on top (like the picture earlier) and is obviously designed to have the hot coolant from the head flow through the core first before hitting the valve. Therefore the "Back/Bottom" mantra is correct and Jlevie is actually wrong.

[cabin]

Good to know. I have my intake manifold off right now to clean up my coolant lines, and I was almost going to switch them around due to what was brought up in this thread.

[Fidhle007]

I'm guessing everyone who is convinced the coolant hoses should be hooked up backwards lives in a warm climate...

[samiam3356]

Warmer climate FTW! Interesting find. Going to be tearing mine apart soon. Think I will yank the heater core out and take some pics. Mines on top as well.