Oil in plenum bolt hole

[blindbandit]

 

Merry Christmas all,

 

Has anyone seen this before? Oil keeps coming up through the bolt hole in the plenum chamber?

I haven't had the chance to take it off yet, but before I do I thought I'd pick your brains.

 

Many thanks

[Tricky-Ricky]

That's a very odd one, as due to plenum vacuum if there was a leak it would suck the oil into the plenum, so it cant be coming in for the plenum itself, its got to be coming for somewhere else

[blindbandit]

That's what I thought, but there's no oil drip or spatter and nothing but the bonnet above??

 

 

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[Irn Bru]

I can't see how that is coming from anywhere other than from the plenum chamber, there is no trace of oil leading to the bolt hole. Have you checked the bolts are tight ?. In any case I'd be having that plenum off and get the chamber checked and cleaned out, refit and torque down the bolts to the proper settings and keep an eye on it.

 

You haven't topped up the oil lately by any chance and perhaps spilled some and it's found its way into the bolt hole ?!?!

Edited December 26, 2016 by Irn Bru

[Willsy1980]

If you look closely, around the top of the bolthole. It looks like the plenum is cracked, that could cause a capillary action and allow the oil to seep up and out. If you take that off, be prepared to replace it as torquing it down could finish it off.

[blindbandit]

Cheers willsy, I work in NDT so I'll dye penetrant test it when I take if off. I'll investigate and post the findings.

 

 

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[Willsy1980]

Fingers crossed i'm wrong, but have always wondered if the constant heating and cooling of the cast aluminium would be an issue, could always have been a flaw in the cast that was never detected. Good luck with the tests

[Mopedmark]

I does look like a crack but I think it's just the outer edge of the oil stain, I have members Plenums sent to me fairly regular and Never had one cracked or damaged in anyway But I have had some with staining here

[Tricky-Ricky]

The staining area looks quite big, and although i could understand getting capillary action from a crack, the inside of the plenum doesn't have an oil pooling area that could supply that much oil, and as i said if a crack opened with heat, the plenum vacuum would just suck all the oil inside.

[davey_83]

Looks to me like the oil chamber in the lower plenum (which normally see oil from the pcv valve) is expelling oil up the bolt via the treads, then pooling on the top of the plenum.

 

Possibly the plenum itself hasn't been torqued down in the right sequence previously, leading to the centre sitting slightly proud and therefore the bolt not being able to tighten down correctly.

 

PS the bolts themselves on the inside, aren't exposed to vacuum.

[Tricky-Ricky]

Looks to me like the oil chamber in the lower plenum (which normally see oil from the pcv valve) is expelling oil up the bolt via the treads, then pooling on the top of the plenum.

 

Possibly the plenum itself hasn't been torqued down in the right sequence previously, leading to the centre sitting slightly proud and therefore the bolt not being able to tighten down correctly.

 

PS the bolts themselves on the inside, aren't exposed to vacuum.

 

 

Yes but if the bolt was not torqued down enough for oil to be getting into the drilling, there would also be a vacuum

Plus the oil in the plenum would also have to go uphill in order to be drawn into the drilling..

 

You can clearly see in this pic that the central posts are above the oil pooling area, and should this leak for whatever reason it would receive a vacuum all the time the engine is running, and at no time would there be any pressure, so if it was due to capillary action the oil would be sucked back as soon as the engine was running.

 

Edited December 27, 2016 by Tricky-Ricky