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2004 330ci (6MT Swap)
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Discussion Starter · #1 · (Edited)
I am currently in the middle of a full rebuild and have come across a $70 part that "needs" to be replaced because the $1 o-ring does not have a part number... The part being the non return valve in the cylinder head.

Before buying and testing o-rings out, I wanted to know if anyone has found an o-ring that works for this part so we don't have to buy brand new assemblies for a simple o ring.
 

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E30M3 Race F10 535 R1150Rt M Coupe
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Too deep in to save $$. What if the O Ring fails prematurely because cheap?

Oil with draining back out of the head/lifters and every morning you'll have a tappety tap car for the first 2 minutes.
 

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2004 330ci (6MT Swap)
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Discussion Starter · #4 ·
I did not bother trying to look it up on realoem.com, but can’t you just measure the old one?
Edit: I see realoem.com does not show the o-ring, just the non-return valve.
Yeah you won't be finding a part # for the o ring. It just doesn't exist. I did take some measurements of the old flattened oring. A brand new one off a new valve would be best but from my measurements I can guess it is a 14mm ID with a 1.5mm cross section. You'd be surprised how hard it is to find correct size o-rings that don't require you to buy 50x and your already $30 deep with shipping.

However, after scouring site after site for over an hour, I did find this website: FKM O-ring 14 x 1.5mm Minimum 10 pcs
Priced how I think orings should be priced and doesn't cost a lot for shipping. I would be in $6. Plus it says it made with genuine Viton

Too deep in to save $$. What if the O Ring fails prematurely because cheap?

Oil with draining back out of the head/lifters and every morning you'll have a tappety tap car for the first 2 minutes.
And this is another concern. I'm not an oring expert and I don't know how to tell what's good and what's not. To be honest, I never even thought about varying qualities of orings.

Is it worth spending the $70 and having peace of mind? Or do I become the guinea pig to see if I can find a working solution? What would be the worst that can happen if the o ring fails? Tapping on startup for a couple of min? Anything else?
 

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2004 330ci (6MT Swap)
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109 Posts
Discussion Starter · #6 ·
Why disturb the valve/O-ring? Leave it alone and it should be fine. Unless the O-ring is broken I wouldn't worry about it as very little pressure to cause leaking with 4" of oil on this earth gravity (I would worry if we live in the Black Hole though).
Long story short, I have 2 heads and needed to transfer the valve to the other head. aka it needed to be disturbed. The o ring was very very hard and I could not in good faith just plop that into the other head without replacing lol. But you do have a point about it being very low pressure. So maybe I shouldn't be as worrisome as I am being. I can always test and pour oil into that galley and see if any passes thru before installing the head on the block
 

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Long story short, I have 2 heads and needed to transfer the valve to the other head. aka it needed to be disturbed.
No reasons to remove the check valve when transfer the valves -- not related.
The o ring was very very hard and I could not in good faith just plop that into the other head without replacing lol.
with the head bolted on the block, the O-ring is clamped shut and no where to shift.
I can always test and pour oil into that galley and see if any passes thru before installing the head on the block
Do this. I would also test the head chambers for any leaks via the closed valves -- pour gasoline on the head chambers with no cams, and if no leaking in 5 minutes then they are passed.
 

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2002 330ci auto
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I don't see why a new viton o-ring would fail. Get the replacement and if it fits snug into the bore then it'll be fine.

Also out of curiousity, do you have a scale small enough to measure the old o-ring? From the weight and size of the o-ring you can tell what material it's made from. Probably viton in this case.
 
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