Volvo 850 heater core o-ring question

[JimBee]

Are the firewall and lower pipe-to-heater core manifold 0-rings the same?

[erikv11]

Different. From the distant past (viewtopic.php?t=34358):

"... I have an unused, genuine Volvo o-ring and clip kit for the coupler, and I can see those o-rings in the kit are definitely smaller than the ones currently on the pipes at the heater end."

abscate will have an opinion, stay tuned ...

[scot850]

Abscate had a list of 'O'-rings somewhere on MVS.

I looked up on a Volvo dealer website, and they sell a kit of 'O' rings for the firewall coupler for about $49 CDN. None of the drawings specify part numbers. I could only find one for the connections to the heater core.

I have a new firewall coupler for a V/S/C70 which is OE but the rings are not individually numbered. Are 850 parts the same? I have an OE hard copy 98 V/S/C70 parts book. I will have a look and see if they are specified there?

Neil.

[abscate]

More discussion here

viewtopic.php?t=98579

I would put your 1996 into the Volvo parts web store engine to confirm these.

Also see measurements on them here

[JimBee]

I checked with the local Volvo dealership. Tech sent me the blowup. There's a #29 pointer to that area but its for the anchor screw that holds the pipes into the lower manifold. Nothing for the o-rings.
I have a set of those pipes somewhere, If I can find it, I"ll get a diameter reading from with my digital micrometer and see what AIT has to offer.

[abscate]

99% certain the firewall orings and the core/inner pipe orings are different


Let’s put that info both here and in the master o ring thread

Two comments

The T25 thst hold the pipes in is shown backwards in the diagram

There are two different types of firewall connections depending on how deep the yellow snap connectors are, covered in thread above

[scot850]

Not sure if this really help, but I have a heater pipe connector for the firewall. Can't recall if it was for an 850 or V/S70. Anyway, it is a genuine part so I opened it to check the 'O' rings used as they are included as part of the piece.

I also looked up the heater core and firewall junction and the 'O' rings are listed for the core itself but none are listed for the junction part and that is in a genuine 1998 Volvo P80 hard copy parts book:

Heater core parts listing

PXL_20230501_222547246.MP.jpg (284.87 KiB) Viewed 771 times

I removed the 2 x 'O' rings from the engine side of the connector:

Heater junction seals on engine side

PXL_20230501_224652927.jpg (163.15 KiB) Viewed 771 times

The size of the 'O'-rings are:

Engine side O ring

PXL_20230501_224746427.jpg (500.78 KiB) Viewed 771 times

The thickness of the 'O' ring was harder to determine but it is this +/- 0.1mm

O ring thickness

PXL_20230501_224939178.jpg (412.51 KiB) Viewed 771 times

I did not pull the ones on the inner side as they sit in a tight recess and I didn't want to damage the seals trying to pick them out. Sorry!

Neil.

[JimBee]

New data.
I found a set of the aluminum pipes from inside a heater core i pulled from a junk yard car.
The diameter of the pipe at the lower end is 5/8", so those o-rings are much smaller than the upper firewall end o-rings.
NAPA has the right ones. I took my pipes into the NAPA store and the clerk went through 4 o-ring kits before we found the exact right fit. The pipes had the original o-rings in place, which helped a little in determining the thickness of the ring. The way the o-ring beds into the flange that backs it, also helps to determine the thickness.
The NAPA kit number is 727-2502
The specific o-ring from that kit is 727-2114.

One more thing: elastomeric composition: There are two composites: Nitrile and Neoprene. NAPA's set contains only the Nitrile,so we did a quick search while i was there and came up with Nitrile is best suited for auto coolant exposure. Neoprene are best suited for high pressure, caustic and, I think it said, A/C refrigerants.
BUT WAIT:
Not every source agrees that Nitrile is best for cooling systems"
MRS Rubber Supply in Massachusetts seems to be authoritative; they make both Nitrile and Neoprene o-rings and lots of other rubber components. Their website indicates Neoprene for a variety of applications, including engine coolant, oils, hydraulic fluids, etc., (contradicting other online sources). https://www.manuf-rubber.com/news/what- ... -material/

So I called them and got an official (I thnk) technical answer: nitrile they say is the best for engine coolant (antifreeze). That seems to be the official opinion. I didn't ask if you can buy just 2 . Most likely, they sell bulk packs but it's probably a good source for other o-rings and rubber parts.
So, NITRILE seems the way to go for the heater core o-rings and NAPA appears to have what you need.
JB

[erikv11]

New data.
I found a set of the aluminum pipes from inside a heater core i pulled from a junk yard car.
The diameter of the pipe at the lower end is 5/8", so those o-rings are much smaller than the upper firewall end o-rings.
...

Correct, except for the new data part. See the link from 2010 up there at the top of this thread. There are also threads from that 2010 era concluding that nitrile is the preferred material for this application, so that's good confirmation.

Thanks for measuring them and refreshing the discussion, these data will be useful going forward!

[abscate]

We have officially thrashed this one to death. No complaints, documenting this stuff is fantastic when you are on the road in backwoods Egypt and have a leaky o-ring and no clue what size it is…