Have I got a story for you guys. Got the turbos installed a couple days ago. I let it idle with the existing engine oil because it was still fresh. Checked for leaks while it warmed up, everything checked out and looked good. I drove it up on ramps, changed out oil with brand new Motorcraft 500S filter and full synthetic 5W-30. I cleared engine codes with FORSCAN and took it for a test drive and felt good while taking it easy. I drove it for about 10 minutes and got the urge to give it a little juice and make sure it was making good boost. Pulled nicely and upon deceleration, to my horror I saw a cloud of white smoke out the rear. Freaking out now, I took it back to the shop and looked everything over.
Oil was dripping from the turbos, and the rear one was smoking because that one was hitting the exhaust as it dripped. At first I thought the banjo fittings were the culprit because I couldn't source new crush washers from the local dealer and reused them, but upon closer inspection, no oil on top, just on bottom, and it looked like it was coming from the area of the hose clamp on the turbo inlet. I pulled off the front turbo's intake hose and I saw oil pooled on the cold side of the compressor wheel, so I know it was coming from the turbo seals and not from somewhere else like PCV at the WOT port. I racked my brain for a couple of days and did some research.
At first I was thinking bad turbo seals, but on brand new turbos, I wanted to believe that CF Power didn't stiff me with garbage turbos right from their manufacturer. My research told me that usually when a brand new turbo leaks, it's because of either oil drainage problems or excessive crankcase pressure. Almost never to they leak right from the get go.
I checked the drain lines on the turbos. Ran water through both, no visible signs of oil deposits, and no restriction on the flow of water. Next I did a compression check to see if the rings were totally shot. Got 150-155 across the board except for one cylinder that read 180. At this point I was thinking my engine is completely toast and I need to drop three grand on a new one. But I looked up the specs on this engine in the Ford shop manual, and it says those compression numbers are within spec. A wet test shows that all of them read about 180, so I know I've got some blowby, but nothing crazy according to Ford's specs. I figure that one cylinder had so much oil in there from the turbos blowing oil that it was the same as a wet test.
Next I put my hand over the oil fill hole at idle, and pressure would build up after about 5 seconds and burp out after I took my hand off. Nothing crazy, but I thought it was weird that it was pressurizing like that at idle. Then I thought for a minute, why the heck wasn't this being evacuated through the PCV valve? The vacuum on the intake manifold should be enough to pull these gases out, right?
And then it occurred to me. I thought maybe the UPR catch can check valve doesn't have enough flow to keep up with the blowby, so in an act of desperation, I took it off and put the stock PCV hoses back on. Put my hand over the oil fill, no pressure build like before. Now at this point, I got pretty excited, because I thought I was gonna need to pull my engine and replace it before I did this test.
I took it for a test drive, and other than residual oil burn off the exhaust, no smoke at all under light load and low rpm. I drove it nice like that for about 5 minutes to get the engine up to temp. and I did a WOT pull to ~4500 rpm and still nothing. Mind you, before it was puking smoke out the exhaust by that RPM before I switched the factory PCV hoses back on. Then I drove it up on the freeway and did several red line pulls, and absolutely no more smoke. It took a while to burn off all that oil that had covered the back turbo's exhaust pipe, but as I took it to the gas station and filled it up, idling for 10 minutes in the process, the smell all but went away. I filled up, checked the oil, and off I went again. Still nothing as I did one more red line pull for good measure before getting home.
Moral of the story, if you have a high mileage engine with some blowby, don't install a check valve on the manifold vacuum that restricts down to 3/16" when the original PCV hose is closer to 3/4".
