If 14psi is applied should my AOS leak air from top?

[Dan944t]

Hi guys , just performing a smoke test through my turbo pipes ect to eliminate any boost leaks ect before a tune in near future,…..and i have seen smoke only coming out from the very top of the AOS unit around the edge at the top , where it has the small slots ……just to make it clear this is leaking from the top where the top and side silicone/rubber pipe area and not the top oil cap ,..that’s all fine along with new seals when i rebuilt everything . sure wish i smoke tested back then.

my question is , if applying 14psi of air preasure should this leak at all? i’m assuming it shouldn’t wether under vacume or preasure ?


thanks for any advice known

all the best
Daniel

 

[Eldavo]

14psi is quite a lot to be performing a smoke test with - pretty sure the tester I borrowed is only about 3-5 psi.

That said, no - the AOS shouldn’t leak from the top. In rebuilding my engine I put a new O-ring in the AOS, I can’t remember the dimensions exactly but Google is your friend. A smear of silicon sealant to hold it in place and then I hot glued a bead around the edge of the cap when it was back on to hold it on as it’s very difficult to remove the cap without damaging it. If I was in your situation, given how much of a faff it is to access it, I’d be inclined to just silicone the cap on from the outside.

 

[944Turbo]

I believe there is a metal pipe under the manifold that sucks the gases from there into the turbo inlet - it might* have a small amount of 'leakage' to stop too much vacuum forming in the crankcase?
As an aside that metal pipe can get cruddy - I think carbon and scale from that pipe killed my cars original turbo as it exited into the J-boot just in front of it. I put a small catch can in circuit with it to prevent it happening again
Tony

* Or not as Eldavo says!

 

[Dan944t]

thanks guys ,…

yes i originally tested to 12 psi which is the max that my smoke machine advised ,.. bur obviously i wanted to see if 14 would show anything up as i’ve read sometimes the lower psi doesn’t show up . glad i did now cos that is gonna bug me,…and like you i thought i may seal it up at this point as i’m sure not taking the turbo down pipe off now ,… i remember looking at it thinking i’m sure that’s made to come off, but obviously slipped through the net.

i may ruff it up and alcohol wipe it and epoxy it all around then test again…

on the good side out of testing ,…thankfully only this and 2 tiny pin holes on my stainless jboot i made were leaking smoke , and i turnt the engine with butterfly wedged open to test the manifolds /turbo and exhuast ,..and a single leak , extremely happy —

Now back off with the fuel rail and injectors and manifold i guess [8|]

 

[TTM]

It should not leak but if it does and if it is not a huge leak I would sleep on it. I believe the level of vacuum in the pipe when the turbo is on boost will always be high enough to pull crankcase gases out, and by the time it does not anymore then piston rings may be completely worn out.

 

[Dan944t]

It should not leak but if it does and if it is not a huge leak I would sleep on it. I believe the level of vacuum in the pipe when the turbo is on boost will always be high enough to pull crankcase gases out, and by the time it does not anymore then piston rings may be completely worn out.

thankyou,…

i remmwber ready such things but wasn’t 100% as it was most likely an american forum a long time ago and i could have remmwbered wrongly so thought i’d ask. i also have a catch can in route with large internal diameter piping , wether that’s good or bad we will see,..only that i had oil in the intercooler pipes before i did this conversion with the bigger hx35 twin scroll ect ,…. but after the full engine forge build i rebuilt my standard kkk and saw oil in the intercooler pipes ,..which is why i installed the catch can with decent sized pipes now. i couldn’t understand why the oil but i read it’s supposed to be normal for these to have a tea spoon in the pipes??

we’ll see how consumption goes when i get this on the road after tune,…but for now i am going to have to strip manifold / rail /injectors and i’ve decided i will get that top cap off,..replace the large oring and reseal the lid back,…( won’t be able to rest a surrey if i don’t do it right)

i expect to use more oil this time round becuase of the larger set up but we will see how it goes i suppose

thanks for all advise great help

Daniel

 

[944Turbo]

Oil in the intercooler plumbing comes from a couple of sources - worn turbo oil seals, which can leak directly into the pipes - but also the AOS doesn't completely separate all the oil / air so you have warm 'oil vapour filled' air being sucked into the turbo inlet where it is then cooled in the IC and IC pipes and condenses. The catch can should catch most it it if it is plumbed in between the pipes from the AOS and the intake.

 

[Dan944t]

thanks stuart i thought so,… i think at first i was concerned about blowby by the rings , and as they are new i wondered if i had fitted incorrectly ect , but i’ve documented my build with photos all way through for my history so i checked my work and all seems right. i then installed my catch can but must check i’ve routed it correctly ,. i think/ hope that i have [8|]