Heater Core Valve Question

[nlav26]

I had a nasty leak coming from the heater core valve, which was shooting coolant onto my ankle by the pedals. After a bit of searching it seems this is a fairly common E30 issue, whether from the core itself, the valve, or one of the pipes. I considered buying a new valve but it's a 300 dollar part and after reading reviews on multiple sites, people state that the brand new part was leaking upon install. I decided to disassemble the valve and found the o-ring to be destroyed. The one in my car is only 2 years old, so there is obviously either some assembly flaw at the factory that makes these, or a poor choice of o-ring material (to me it looks deformed from heat). Next step is to find an appropriately sized, high temp o-ring to replace it with. Unfortunately when I took the valve apart I lost track of the orientation of this part on the inside (pics attached). Can someone explain to me what this piece is, how this valve actually functions, and hopefully tell me which is the correct orientation for this piece when I reassemble it (I labeled the pics Option 1 and 2)? This job was a real pain (literally) because I disassembled the valve while still connected in the car (S52 swap so I would have had to remove the intake manifold to access the heater pipes at the firewall in order to remove the entire thing). The last thing I want is to put this valve back together incorrectly and have it either not function properly or leak. Any help would be appreciated!

Nick

[Northern]

Looks like they just rammed the valve home and tore the oring on install.
Not sure which way it goes, but thank you for documenting this because I'll be following in your footsteps this winter...

[KIRIEIW]

Just put a brand new heater valve in my car today, after a failed rebuild attempt rebuilding the original 30yr old valve. Crazy how different the new valve looks.. Let us know what size O ring you end up using, I wouldn't waist another $2xx on a valve. Just replace the O ring and call it a day.

Can't comment how it goes back together though.. Wish I would have seen this just a bit earlier and I could have had answer but it's already in the car now...

[ZeKahr]

Can someone explain to me what this piece is, how this valve actually functions, and hopefully tell me which is the correct orientation for this piece when I reassemble it (I labeled the pics Option 1 and 2)?

As per the E30 online wiring diagrams, heater valve is an on/off solenoid that allows water to flow through the heater core when the temperature knob is rotated 20 degrees from the coldest position. Assuming the temperature knob has 270 degrees of rotation, the valve is responsible for only about 7% of the total temperature blending; the remaining 93% of the temperature blending is handled by the blend door (also controlled by the temperature knob) in the heater box.

As to why BMW added an on/off solenoid to help control temperature blending when they could of simply used the blend door to control temperature blending is anyone’s guess; my theory is that it allows the AC to be more efficient - one side of the heater core is always exposed (even with the blend door fully shut) and this allows a bit of heat to leak out. I unplugged mine and am still getting cold AC. The problem this valve creates is it allows coolant to stagnate in the heater core, allowing for degree buildup and clogging of the core.

[cornchip]

RestoreIt has a video on this I believe.

[nlav26]

UPDATE: I replaced the o-ring with Mcmaster p/n 1283N32. Ran it for about 20 min last night with no leaks. Much cheaper than risking $300 on a new valve (which may still leak based on the reviews I've read). This is a good option for someone with an M52/S52 swap who doesn't have easy access to the heater hoses at the firewall. I'll report back if anything changes but so far so good. Also, per my original post, I reassembled per my photo labeled Option 1.

[cornchip]

UPDATE: I replaced the o-ring with Mcmaster p/n 1283N32. Ran it for about 20 min last night with no leaks. Much cheaper than risking $300 on a new valve (which may still leak based on the reviews I've read). This is a good option for someone with an M52/S52 swap who doesn't have easy access to the heater hoses at the firewall. I'll report back if anything changes but so far so good. Also, per my original post, I reassembled per my photo labeled Option 1.

very cool - nice work man!