Warp Factor

It's an ECS supercharger kit, been on the car for about ten+ years, with no major problems.

But now, when I'm over 5000 rpm at full boost, I'm blowing quite a bit of blue smoke out the back. Doesn't happen at 6000 rpm, part throttle, or under 8 pounds boost at full thottke. No unusual noises, and no noticeable increase in oil consumption between changes (but that might be because street driving, I don't spend all that much time over 5000 rpm and over 8 pounds of boost).

Would this more likely be an engine problem, or sucking some engine oil past worn supercharger seals, since vacuum levels in the shaft seal area would be expected to increase with increased power levels?

I haven't yet done a leakdown test, because it's such a pain in the azz on a C5, so I thought I'd ask you guys first what is most likely to be going on.

stevieturbo

I would be surprised if the cause of the oil smoke was because of the supercharger unit itself.

I would be inspecting plugs and doing a compression test though

Warp Factor

Thanks for responding, Stevie.
I was hoping that someone might respond saying, "Yup, it's a known issue when the impeller shaft seal (separating the the gearcase from the impeller) goes bad", but maybe that's not going to happen.

So I suppose the first and simplest step might be to pull the hose off the bottom of the intercooler to see if there's oil in the hose or the intercooler. Oil couldn't get from the blower to the intake manifold without passing through there, and one might expect some accumulation at the bottom of the intercooler if oil was passing through it.

stevieturbo

Even if that seal was bad, once boost is built up in there, that should help prevent any oil entering that area simply because of the pressure in the housing.

But what you're saying sounds like a fair amount of oil if it's visible. But definitely yes check hoses...but for a large amount to get right through all the pipes, the IC and then intake and cause lots of smoke....I just cant see it without some other symptoms too. Even oil coming out of the BOV ?

Warp Factor

There would be vacuum at the blower inlet, and probably also around the impeller shaft seal area. And the higher the boost and rpm, the more vacuum there would be between the air filter and the blower.

No noticeable oil coming out the BOV (at least not enough to saturate the filter and drip). No noticeable oil residue in the vicinity of the crankcase breather on the valve cover.

stevieturbo

The only place there would be vac....or lower pressure as opposed to actual vacuum is the inlet. Even behind the compressor wheel is well within the housing which would see positive pressure.

Is this a repeatable thing ? like very time you hit 5k it does it ? Or just occasionally ?

Warp Factor

Well goldangit, the car seems to have fixed itself. Nothin' out the back over the last two days except for a little black smoke from running pig-rich under boost, and tire smoke.

Sometimes ya got to scare a car into submission. Like, I was about to pour a can of "Ring Job, Piston Repair and Total Rebuild" from the auto parts store into the oil filler, and then a little voice (probably the engine talking), said, "Try me once more before you do that chit".

On a less Zen level, maybe some oil or fuel residue accumulated at the bottom of the intake manifold during slower driving (or winter storage), and it took a few high-airflow situations to blow it out.

Still looking for input on this.

JLayer

My seals were bad in my Paxton (Novi 2000) but never noticed smoke out the back when I was in boost. I had pretty big oil puddles under the car near the front. At first I thought it was the front seal of the block but after looking closer, it was coming out of the J-tube.

To me it sounds like it something else.

neverstop

if the blower seal is bad you'll see oil streaks in the rubber tube that is the outlet on the supercharger. easy enough to check but this sounds like something else, perhaps valve stem seals?

stevieturbo

Valve stems seals could not leak oil into the inlet under boost...because of the boost.

And even under vac them and the guides would need to be very bad for it to cause visible smoke.

Warp Factor

Update:
The problem seems to have been solved by replacing a couple of injectors which were leaking when the engine was off. My conjecture is that the fuel left some less volatile fuel residues in the intake tract (resembling oil more than gasoline), which would be blown on through and burned at higher power levels and air velocities, producing the blue smoke.