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Discussion Starter #1
I'm leaning towards valve seals, but I'm not sure. Here's the symptoms:

I'm burning oil somewhere. I get the blue smoke, but kind of intermittently. There's a small amount of smoke under idle, and I get big puffs when I take off from a stop, but then the smoke stops during regular driving. The turbo has no shaft play at all, which is kind of why I doubt it's the problem.

Obviously, the Aero has the TD04 turbo, but I do have a spare T25 from my old CS lying around. Assuming it is the turbo that is bad, I know the T25 will fit, but does anyone know how the different turbo will affect performance? I'm guessing I'll loose some top end, but I'm dumb with this kind of thing.

Now, assuming it is the valve seals, is that something that a moderately advanced amateur could do? Can it be done without removing the head?
 

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You could try to narrow it down a bit.

For example, if the turbo is leaking oil directly into the exhaust, and it is burning there and in the catalytic converter, some unburned oil would be found inside the exhaust tip.

If it is going into the intake you would find some fresh oil in the delivery pipe and on top of the throttle plate. A little would be normal, but enough to cause smoke from the exhaust would be very noticable.

If the oil is being burned in the engine, and there is none in the intake, then it can only originate in the engine.

...not fool-proof, but a little closer.
 

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What weight of oil are you using and is it synthetic or conventional?

I find these engines can be quite fussy about viscosity when hot and if you are using less than 50 weight synthetic or 40 weight conventional then that might result in the type of blue smoke you are describing.

I recommend 5W50 synthetic or 10W 40 conventional oil. If you run Castrol conventional oil use 20W 50. For winter use the same synthetic or 10W 30 conventional oil If you use Castrol conventional oil in winter consider using 10W 40 or if you use 10 W 30 put up with a little smoking on warmer days. By warmer I mean above minus 10 C!

I would never use a 5W conventional oil ever unless I was in the Arctic (I'm in Calgary Alberta Canada so my winter oil needs to work down to minus 40C.). I would not use 0 weight synthetics nor any 5W that wasn't also 50. 10W 40 synthetic or 15W 40 would be fine for warmer climes.

Turbo seals will leak oil directly into the exhaust under boost but should not leak when idling. The compressor side never goes into vacuum. If the exhaust side seals go then you should get continuous heavy smoke under boost.

Intake valve seals will leak at idle and on lift off but should not leak under boost as any leakeage would blow up the guides not down.
 

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Discussion Starter #4
PMI said:
you would find some fresh oil in the delivery pipe and on top of the throttle plate.
Ok well I can't believe I didn't think to look there. The top of the throttle plate is.. well oiled.

(The exhaust had no unburned oil, and the compressor side of the turbo was dry and clean. I'm pretty sure the turbine side was oil free when I put on my 3" exhaust a few weeks ago, too.)
Superaero said:
What weight of oil are you using and is it synthetic or conventional?

[...]

Turbo seals will leak oil directly into the exhaust under boost but should not leak when idling. The compressor side never goes into vacuum. If the exhaust side seals go then you should get continuous heavy smoke under boost.

Intake valve seals will leak at idle and on lift off but should not leak under boost as any leakeage would blow up the guides not down.
I've been using Castrol GTX 10w30 ever since I "discovered" the oil disappearing problem. Mobil1 just got too expensive to be putting in a quart a week. :( I've got an oil change coming up soon, so I'll try switching to 20w50 Castrol this time.

Sounds like I'll be doing my first valve seal job sometime this summer. Oh baby.
 

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It might be worth it to try to find out if there is a lot of oil in the PCV valve and PCV lines, and then what the top of the engine looks like under the valve cover.
 

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My 86 would smoke intermittently on Castrol 10W 30. I used 10W 40 for winter use and 20W 50 for summer.


Synthetic is even better.
 
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