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Old 10-27-2014, 02:34 PM   #1
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Default Blow-by (not the typical "have you searched yet")

So I'm having a blow by issue but it's not exactly run of the mill, and hoping one of you guys have some ideas. As a summary if you don't want to keep reading, oil coming out from oil cap, proper PCV system, rebuilt engine, new turbo.....

Recently rebuilt my 1.8 as I was pulling the engine to replace the clutch and rear main, and ended up going all out with ARP, new bearings, rings, seals, cleaning pistons & looking for det, and checking clearances. Ended up being in spiffy shape but I did find something got into my first couple main bearings. Checked all tolerances including ring gap and everything was in spec.

After rebuild, put on a new garrett 2554 and good to go. Only there is an issue now.....I am getting some smoke (oil) on long idle and on first acceleration once the engine is up to temp. This is most certainly not coolant, my oil cap isn't milky in the least. Pulled my plugs, and they look brand new even after 600 miles and my power is really excellent. This kinda rules out an issue with the rings ( I compression checked too and all the numbers are even), the valve seals, or anything else within the engine (to my knowledge???). It's pointing to the turbo, but the key is that I have been seeing oil leaking around my oil cap. I think there is blow by which is preventing the turbo to drain oil (and there are no kinks in the drain fwiw, and running a .850 restrictor as it's journal bearing), which in turn is causing smoke.

For the PCV I am running the Mazda (323?) turbo right to the intake mani, and for the CCV I am running a line from the VC to a harbor freight catch can, over to the turbo compressor inlet.

As far as vacuum lines the only thing I changed was the charcoal canister which I blocked off with a nipple on the intake manifold.

Why would I be seeing oil come out from the oil cap? I covered all of the basics which I found searching, but I must be missing something?
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Old 10-27-2014, 05:00 PM   #2
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This may be a stupid recommendation, but sometimes the easiest things are overlooked. Is the oil cap gasket in good condition? I've had a few go bad and cause leaks before.
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Old 10-27-2014, 06:17 PM   #3
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Quote:
Originally Posted by dieselmiata View Post
This may be a stupid recommendation, but sometimes the easiest things are overlooked. Is the oil cap gasket in good condition? I've had a few go bad and cause leaks before.
Mine is rock hard, but isn't there supposed to be no real pressure there? I thought about this first, but this thread made me question....Oil cap leaking? - MX-5 Miata Forum
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Old 10-27-2014, 06:23 PM   #4
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There's no pressure, but try leaving the oil cap off and starting your car. You'll be in a mad dash to get the cap back on. Think open milk container on a bumpy road.
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