current opinions: best value Volvo 850 heater core

[JimBee]

For reference: viewtopic.php?t=100473&hilit=Heater+core .
The pennies in that picture are resting inside the boss on top of the ridge seats so you can't see the seats.

The surface "boss" openings in the mold aren't carefully spec'd. Their job is to guide the pipes into the bores. Because of the restricted view in that area, the larger boss openings are very helpful.
Inside the boss the bores appear to be uniformly round and the ridge seats, which are recessed only about the thickness of the o-ring, seems to be flat. Well, they're molded so they aren't glass-smooth flat, but pretty close. That mating point between the ridges and the o-rings is what makes the seal. Obviously the o-rings need to be fully and firmly seated to make the connection leak proof.

As I previously mentioned I have a pipe set from a junked 850, so I fitted the o-rings that came with the Nissans core to the pipes and holding the core securely, with no visual restrictions, I couldn't press the o-rings fitted onto the pipes fully into the bores so they would reach the ridge seat. I can't imagine getting them properly seated in the dash without significant force that would be hard to carefully apply at that angle.

ALSO: I compared the Nissans o-rings that came with the core to the NAPA 2114's. They're extremely close. I measured them installed on my spare pipe set. The Nissans ones measure at ~ 20.65 mm. The NAPA ones are a skillionth thicker at about 20.75 mm. Neither the Nissans nor the NAPA ones installed on the pipes would go into the bores. Off the pipes, they fit tightly, they don't just drop in. (The original o-rings are still on the pipes. Installed, they measure ~20.4 mm.)

The bores that need to accept the o-rings are just under 20.mm (~ 19.8 mm), so the o-rings are supposed to be a squeeze and slightly compression fit around the sides—as well as at the face of the ridge seat. No surprise there. But they can't be distorted at assembly. So that's tricky.

To ease fitment and proper seating, I'll spray the o-rings with silicone.

Then, the center screw that holds the yoke and o-rings firmly seated has to be tight, but tightening it too much I suppose would distort the o-rings and possibly cause a leak. I'm going to check with a Volvo tech on whether there's an nm spec for that.

Without the silicone spray, I can see how it would be easy to hang up and pinch one or both o-rings on the side of the bore and not get them properly seated.

[ZionXIX]

I will say as far as o rings go, I added small washers to the pipeset for a little more compression and I haven't seen a drop since install 6 years ago.