Trying to find oil leakage XUD9

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CPtje
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Re: Trying to find oil leakage XUD9

Post by CPtje »

Hi guys, is there a way to check the crankcase breather valve.
I took it off and could easily blow through it from both sides. Is this normally the way it should be?

Just to be sure, guess it's this part.
crankcase breather valve
crankcase breather valve

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white exec
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Re: Trying to find oil leakage XUD9

Post by white exec »

I have a similar one on XM, which removes crankcase (oily) fumes from the rocker cover, and vents to intake duct (low suction). Have had ours leak oil, because of a poor O-ring seal where it slots into the intake duct, and a slightly sloppy fit.

Never investigated the inner workings, although a good few petrol ones explained on the web, where the flow through (usually rocker cover to high-vacuum inlet manifold) is variably metered according to engine revs. The diesel versions may be a whole lot simpler, and maybe even just a one-way valve (spring+diaphragm).

Someone here will surely know!

moizeau
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Re: Trying to find oil leakage XUD9

Post by moizeau »

Mine on the BX blew both ways with a gauze filter in the middle

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CPtje
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What went wrong? Did I overtighten?

Post by CPtje »

I had some leakage at the left side of the seal after 100km, so I tightened the left bolt. Everything looked good for about another 100km. Then things went terribly wrong and the cover seal was torn to pieces during my trip back home.
Did I overtighten the rocker cover?
IMG_20200523_121223.jpg
IMG_20200523_121206.jpg
Hopefully nothing more is broken as I drove about a km slowly while the oil lamp went on and off, before being able to park and refill oil. Then slowly home.

Will need to clean a lot.
Going to try to replace the seal again ASAP. How tight should be tight enough? Other advise?
Feeling embarrassed!

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white exec
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Re: Trying to find oil leakage XUD9

Post by white exec »

Bad luck. You'll need to replace that seal again, preferably with another new one.
You might be lucky and be able to clean it up though, and de-oil it.

Get hold of a tube of Hylomar Blue (it's on Amazon).
Clean all the surfaces with solvent (alcohol, petrol...) and apply the Blue thinly to all surfaces (small brush).
Allow to dry off (15-30mins).
You can then position the seal, and it will stay where you put it. Blue works like a post-it note: it stays put, but is separable and repositionable. Can be separated later, if needed.
Tighten down evenly, but don't overdo it.

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CPtje
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Re: Trying to find oil leakage XUD9

Post by CPtje »

Hi Chris,
I used Loctite si 5926 silicone blue. Is that also okay to use?
I only put a thin line on the head.
Then I positioned the seal on the cover without the Loctite.
Then I carefully placed the cover on the line of Loctite and tightened the 3 bolts.
I really did not have the idea that it was too tight but it looks like the cover cut completely through the seal. I know for sure when I remove it.
Really, I'm not that strong so I'm confused that this might be too tight.

Q's:
Is it okay to use the Loctite?
Should I put the silicon on both sides of the seal?
Should it be a thin line or just a very thin film (like putting it on with a finger)?
How do I know that the bolts are tight enough to not leak and not to tight to destroy the seal?

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white exec
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Re: Trying to find oil leakage XUD9

Post by white exec »

The tightening torque for the valve cover is stated in Haynes as 2Nm (1.5 lb.ft), so quite a low figure.
This is to avoid distortion and gasket 'squelch'.

I don't know that Loctite sealant, but it's a silicone one, with a 24hr curing time.
That suggests it remains fluid - and slippery - for a good while, which isn't helpful if there's a risk of the gasket slipping out from between the two surfaces.
The Loctite fluid is also recommended for metal-to-metal work (like cast some cast engine sumps), where gasket slip isn't a consideration.
Silicone products are also not usually good at staying adhered to hot/oily surfaces.

The advantage of the Hylomar Blue (and there may be other similar products) is that it goes from thick liquid to a tacky Post-It like surface quite quickly (eg 10-15 mins), and the grip available is useful in preventing flexible gaskets from 'slipping away'.

GoceKU
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Re: Trying to find oil leakage XUD9

Post by GoceKU »

I've seen this before, it's caused by pressure build up in the crankcase, nothing scary, cheap or damp air filters cause it.

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white exec
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Re: Trying to find oil leakage XUD9

Post by white exec »

Not sure about that. If the breather valve (in your photo) were stuck closed, it could allow pressure to build up in the crankcase, but a wet or blocky air filter would actually increase intake suction, and assist with crankcase fumes removal.