What causes the oil seals to go bad on the stock VGT turbo? - Ford Powerstroke Diesel Forum
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Old 05-24-2011, 06:42 AM
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What causes the oil seals to go bad on the stock VGT turbo?

i just dont get what causes it to fail again. another question i have is why there is only the one seal. its set up like a piston seal so you would think there would atleast be a second seal with the gap in the opposite direction.

anyway, thats a discussion for another thread. i'll just be happy to have the powermax installed and not smoke out the county.
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Old 05-24-2011, 06:52 AM
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There, now we can continue our discussion.

I have heard that kinks or severe bends in the CCV hose can cause your oil seal to blow in the turbo. Mine went out in my truck and with it came a decrease in overall engine performance. It was especially noticeable while towing up a grade.
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Old 05-24-2011, 06:56 AM
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i did check my ccv and even re-routed the hose thinking it could have caused the problem. no luck though.

my other thought is the feed line could have caused it since i still have the one with the flex section. i'm taking that out of the equation when i install the powermax. i'm also installing an egt probe so i know for sure when its safe to shut down. currently i let it idle for a few minutes, but dont know if its long enough to cool it down.
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Old 05-24-2011, 07:03 AM
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I also have my CCV rerouted, although mine is just replumbed to the inside frame rail with an aftermarket breather valve clamped to it. I have verified that it isn't kinked, although I really have no idea what it does when I'm cruising down the road. It's 5/8", oil rated hose, so I would imagine it would be fine.

I also have the flex oil feed line, but I would imagine that both designs (flex and rigid) would ensure adequate oil flow even at peak demand.
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Old 05-24-2011, 07:50 AM
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If you are referring to the floating bearings on the turboshaft then you have hit upon the primary cause of failure in shut down procedure shortcuts. Seizing of a turboshaft is frequently the result of coking due to excessive heat. The shut down procedures for all military vehicles equipped with turbos calls for a cool-down time of five minutes or more in some cases. As the turbo can spin at several tens of thousands of RPMs the need for a nearly frictionless bearing is critical. Unfortunately upon engine shut down the oil that provides the lubrication and cooling for the turboshaft is denied continuous circulation so if temperatures on the turboshaft are consistently higher than the thermal breakdown point of the oil, you get coking. The only way to assess the turboshaft temperature is through an indirect method: either with a pyrometer pre-turbo or post turbo, or perhaps an additional oil temperature sending unit in the vicinity of the VGT piston (I have no idea how that could ever be made to work in practice though). I have a pre-turbo pyrometer and so I have to estimate the heat transfer across the turbo. With a post-turbo pyrometer you'd have a more precise assessment of the heat transfer to the turbo. Obviously synthetic oils are more resistant to the effects of heat and there is variance between synthetics too. As an example Rotella T (full syn 5W40) had a flash point of 399F while the new T6 (full syn 5W40) has a flash point of 446F...the turboshaft can easily get this hot (and even hotter) so a proper cool-down is really important.

Jonathan
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Old 05-24-2011, 07:55 AM
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Don't forget there is an upgraded turbo oil drain line that has less restriction. I your oil is foaming up at all exiting the turbo it will create backpressure and cause turbo seal problems.
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Old 05-24-2011, 08:59 AM
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without knowing egt's i cant say for sure if im allowing enough time for it to cool down, but that will be taken care of before i install the powermax. i plan in putting the probe in the drivers side exhaust manifold. from all the reading i've done this seems to be the spot most use.

I believe the newest drain line is currently on the truck as its a 2006. it looks like it anyway.

the actual bearings arent what is causing it to burn oil though, its the oil seal that does (as far as i know). it basically looks like a piston ring seal and there is only one, whereas on a piston there is usually three so that the gaps dont line up. I dont see how is one ring supposed to work.

Last edited by diablos30; 05-24-2011 at 09:05 AM.
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Old 05-24-2011, 09:20 AM
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Yes I believe '06 has the updated drain. I agree with Howell's post that the turbo is being shut down too hot. Any coke deposits is like running your turbo shaft and seals in sand. Two fixes, idle your engine until your turbo has cooled down or install an electric oil pump which starts up when you shut off the engine (can also be used to pre-oil your engine before startup). I have the electric oil pump as I sometimes park in an underground parkaid so idling your vehicle is strictly inforced.
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Old 05-24-2011, 09:33 AM
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why does the heat affect the oil seal though? i can see it affecting the bearings, but the seal is locked into its groove.
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Old 05-24-2011, 11:11 AM
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Quote:
Originally Posted by diablos30 View Post
why does the heat affect the oil seal though? i can see it affecting the bearings, but the seal is locked into its groove.
Yeah, I guess the title of the thread is a bit misleading. I'll fix it.

BTW, I have a pre-turbo EGT and I don't shut it down above 400*. The journal bearings themselves weren't bad, my oil seals went out as did the OP.
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