Turbo oil return pipe seal

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Turbo oil return pipe seal

Postby HJ2 » Sat 08.04.2017, 19:55

Evening all,

I have a small problem I'd like to share and perhaps get some good pointers to fix it.

After fitting the Daihatsu Rocky replacement turbo cartridge, A leak developed in the connection between turbo housing and the oil return pipe.
I took the return pipe off and machined the mating surface so it is perfectly flat (it was, but still..) and replaced the gasket with a fresh one.
The effect was none, the gasket developed a leak again.

This must mean that either the surface of the gasket on the turbo housing is warped, or the return pipe is blocked, causing overpressure. Since the pipe was ultrasonically cleaned and inspected, I suspect the surface...

As this is a turbo-off job, I thought I'd cut a seal from 0.8 mm silicon rubber first to seal it off in situ. The pipe is not pressurized, so there is no large force blowing the seal out of position and the silicon rubber should be well able to withstand the max. temperature of the water cooled housing at the location of the mating surface turbo ...

Before I fit the home made gasket...
Any thoughts?
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Re: Turbo oil return pipe seal

Postby Simon_P » Sat 08.04.2017, 21:59

What does the gasket you took off look like? Look for witness marks around the bolt holes.

It would be hard for the turbo casting to not be flat. Check with a mirror and clean the surface with a razor blade.

If you still think it is the surface it might be more successful to use a new gasket and oil proof RTV. The gasket will be more stable and if you let the RTV cure a little before tightening it doesn't all squeeze out.
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Re: Turbo oil return pipe seal

Postby HJ2 » Sun 09.04.2017, 08:11

Simon,

The turbo is almost new and the gasket is even newer, so nothing to scrape off :mrgreen:
Are the bolt holes open to the oil flow? Then that might cause the leak indeed and I need a better seal around the holes. I thought it was only the pipe that needs a good seal between both flanges.

I'll try the custom cut Silicon seal this morning, see what I end up with.
I'll guess I have an increased risk of the bolts becoming loose in this way as here is no 'hard' fit of the mating surfaces. But if it saves me from removing the turbo again... :roll:
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Re: Turbo oil return pipe seal

Postby HJ2 » Sun 09.04.2017, 11:43

Well,


It is leak tight and all the oil scent in the cabin is completely gone.
However I'm not going to leave it as is.

The rubber is soft (obviously) and the layer is too thick, so too much material is squashed out of the mating surfaces.
On the outside this is not a problem, but you don't want to reduce the pipe diameter as this might kill the turbo due to oil starvation. :shock:

This is also the reason why you should not use RTV on the mating surfaces. You never know how much ends up in the pipe, reducing the flow there. As it is not pressurized you don't need much blockage to disturb the flow...

That said, I'll cut another seal but now out of 0.3 mm sheet and see what I'll end up with.
By the way, Google showed a lot of results on warped mating surfaces of turbo oil return pipes. Also my friendly Porsche 911 turbo neighbour immediately said "warped turbo mating surface' without me telling him anything else that there is a leak i can't fix... :banghead:

In the process i replaced the hex. bolts for allen key's for better access from below. If you use an extended Allen key in a socket, removing the pipe is a piece of cake now.
To be continued...
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