Intercooler Pipe Leaking Oil

ekka · Jan 18, 2015

The rubber inter cooler pipe has been replaced 3 times and is now leaking oil again. Will be putting truck in to get it done again under warranty.
Question is should this pipe even have oil in it? Where does it come from?
Looking at fitting a Plasman pipe but read the earlier post which said the turbo is very noisy after also fitting 3" exhaust so am unsure if to go ahead with that mod.
Saw another pipe on evil bay that appears to leave the steel section (muffler?) of the original pipe in place. Has anyone fitted this type?
Only trouble in 82,000k so have been very happy with v9x engine.

Old.Tony · Jan 18, 2015

The oil is fairly normal. Here's how it gets there.

When combustion occurs, a fuel/air mix basically detonates inside the chamber, forcing the piston down. A very small (but enough!) of this super-hot gas sneaks past the piston rings, which is why anyone assembling a block should be staggering the ring gaps - makes a longer path = better seal ... anyway ...

This super-hot gas enters the crankcase which is filled with oil. Because the gas isn't completely burned (because EGR doesn't allow complete combustion) it will make your sump oil black fairly quickly and the hot gas heats the sump oil.

That heating continues until some of the sump oil vaporises (basically becomes oil-steam). The excess pressure in the crankcase (which is pretty much exhaust gas, diesel soot and a small amount of oil vapour) heads towards the PCV (Positive Crankcase Ventilation) outlet in the top of the motor. This is then fed into the air intake just in front of the turbocharger.

So what you end up with is blackened oil sitting in your air intake. But wait, there's more - and there are no steak knives in sight!

You've got oil entering the airstream back in front of the turbocharger which is then rammed through your intercooler and into your intake manifold where it mixes with EGR. EGR is "Exhaust Gas Recirculation" - it's an emission control mechanism that cools (dampens) combustion enough so that NOx is not produced as much during normal driving. What is EGR? Exhaust gas and diesel soot.

So have a think about what is sitting in your intake manifold: blackened sump oil and diesel soot. It's a recipe for molasses!

Anyway, that's where the oil's from. You can fit a catch can (Forefront make good ones) to reduce the oil in the air path, and you might consider cleaning your intercooler afterwards.

auggie · Jan 20, 2015

Spot on old Tony. This hose isn't at fault if some oil is weeping out of it. The common name for the oily gas that's heading back in the intake side of the engine is blowby.

Pretty normal among modern turbo diesels. Used to associate it with older engines with worn out rings but modern high pressure stuff seems to due it from new.

I'd advise you to either go down the EGR blanking plate and catchcan route to minimize this crud building up in your intake or the other option is to get a ecu tune and get the EGR turned off. Pretty sure the 3.0V6 has this option, the YD25 definitely does. You'll still get some blow by oil but long as its not mixing with the EGR soot and forming the solid muck inside the intake no real harm done. Burning a tiny bit of oil wont hurt it. Just make sure your MAF sensor gets a clean when the vehicle goes for service.

Old.Tony · Jan 20, 2015

^ Excellent point. While the MAFS is "upstream" of the PCV feed, sometimes you'll get airflow in the wrong direction, for example when shutting the engine down and there's still a rush of air heading in (even air has momentum, or you wouldn't have to hang on to your hat in a strong wind).

If you want to clean the MAFS yourself, go right ahead - just be careful, it's a rather expensive and delicate piece of equipment if mishandled. Mishandling means dropping it, or trying to stick something inside the little hole in the side where the actual sensor is. Either could destroy it - and without it, your engine won't go well at all.

The best way to clean it (and it's so easy to do) is to get your hands on a can of electrical contact cleaner. These things are spray cans, sometimes labelled "MAFS Cleaner" in an auto store where it's 40% more expensive than last week and you're buying it at 25% off. Jaycar also sells it and I guess any electrical warehouse probably does too. Electricians probably stock several cans so if you have a mate who has a frizzy hairdo, ask him if you can borrow some.

Now remove the MAFS (my garage has a pic of the engine bay showing where it is) and spray the cleaner into that little hole. It should run black for a few seconds and once it's running clear, stop spraying, hold the sensor for 15-20 seconds while the last of the cleaner evaporates then reinstall. Done!

ekka · Jan 22, 2015

Thanks for the great info. They replaced inter cooler hose again today, cannot just replace o ring.
Have ordered a plazmaman pipe so will fit it next week when it arrives.
Also fitting a Redback 3" system next week.
K&N Filter to go in tomorrow so will almost have a new truck to play with.
Next project will be a catch can.
Thanks again for the advise

Old.Tony · Jan 22, 2015

Don't over-oil the K&N filter. Excess oil will depart the filter as droplets which will land on the MAFS and destroy it. Change to a paper filter if going on dirt - the K&N will let too much past.