Water manifold leak, sealing?

[k.alle]

I took the advices and fitted Viton o-rings and silicone grease.
Managed to shave off a bit from one during the install so had to do it twice, might be because of my 7A head with small chamfering?
O-ring size is 15x2.5 mm for reference.

The flange for the funky seal seemed straight.

Pressure tested to 1.5 bar and it didn't drop for at least ~45 min.
I also tested it with vacuum for 5-10 min and it held nicely, so all seems good now.

I was going to upload a picture or two but the forum seems to complain about file type, tried with both .jpg & .png .

[EDIT]
Where's my manners?
Thank you guys for the help!

Added pictures, manifold:
image_78273.jpg

The troublesome o-rings
20200521_131944.jpg

[Error404]

Yes grease to aid install, to help avoid damaging the seal

[k.alle]

Hmm I'll keep Viton in mind if the yellow fails during install, use Viton all the time at work.
Need to find out the sizes though.

Like Andy said, check the flange is flat, use some silicone grease on the seals when you install. Pressure test.

You mean silicone grease as in lube, not a sealant product?

[Error404]

I use Viton o-rings instead. The factory seals are soft and delicate as-said - and they swell in use so they are very much single-use. The o-ring spigot on the water rail is a stainless insert so they hold up well - not the triangular flange though, they corrode nicely.
Like Andy said, check the flange is flat, use some silicone grease on the seals when you install. Pressure test.

[k.alle]

Thanks for the input guys.
Yes the o-rings is yellow.
I'll stick with them since they work properly on the other runners but apply some silicone sealant.

[AndyP]

Just put a straight edge across all the faces as a check. I've seen them corrode too if the correct anti-freeze hasn't been used. I use the high temp silicone sealant.

[John.]

I did these on my S2 last week, the O-rings were yellow and I'm thinking they are original??...mileage is 75k I think. The O-rings that were fitted did appear super soft, I've just used some O-rings from a kit, rubber grease on them and it all fitted up back nice. AndyP Regards manifold being flat, assuming you mean condition around the triangular seal?

[k.alle]

Thanks for that AndyP

Yes that's what I have on right now but without any additional sealant.
They were Victor Reinz and the new ones are OEM, but surely its the same soft material.

What kind of silicone do you use, high temp, specific for water etc?

Good point on the flatness, I'll check that.

[AndyP]

I always put a bit of silicone sealant around the O ring, the yellow ones that come with the Victor Reinz gasket set are quite soft and easy to tear if you don't get them in straight.
Check that your manifold is flat too.

[k.alle]

I got a pressure test kit for the cooling system and found a leak at the water manifold tubing closest to the front.

I have seal replacements (o-rings and funky shape seal) on order but I'm wondering if I should use some additional sealing compound when refitting?
Is there a concensus on how to approach it or should I put my hopes on the new o-ring?

See circled area in picture.