Oil build-up in Airfilter

[benno_84]

Hi guys,

I have a 1998 GU 4.2D with an after market turbo. I have just purchased the vehicle pretty cheap and am trying to give it an overhaul. I am no mechanic and am learning as I go so all your tips and suggestions are really appreciated.

The vehicle has 350, 000 kms on the clock. It runs well, drives well and has no major noises etc. I am replacing the following: oil filter and oil, air filter, fuel filter, coolant, diff oils, transmission oils, transfer case oils. I am also wanting to identify anything which may need doing soon or things that I should look our for.

I would appreciate any advice or resources you can point me to to do this.

I have noticed that some oil is getting into the air filter through what I think is called the blow-over valve ( a hole in the base of the air filter housing). I am wondering what is causing this and if I should be concerned about it?

Thanks

[locks]

G'day Benno does it look a bit like this pic below?

[YNOT]

G'day Benno,

That's a fairly comprehensive service you're doing, I would be adjusting valve clearances while you have the tools out. If you havn't adjusted valves before, check this thread for more info;http://www.nissanpatrol.com.au/forums/showthread.php?603-TB42-Tappet-Adjustment.
Check all your suspension bushes for wear and cracking, and check all you steering components for wear and movement.

As for the oil build up, without seeing it Im' only guessing, but more than likely it's PCV (positive crankcase ventilation) oil mist that has collected. If this is the case you might want to investigate fitting a PCV filter or catch can. A small amount of blowby PCV oil mist is normal, and will increase as the engine wears. But if you remove the oil filler cap with the engine running, and the pressure behind it blows the cap out of your hand, then you have a problem!

Tony

[benno_84]

To Locks

Yeah mate, that was pretty much the state of it when I replaced the filter. Looked exactly the same actually. There was a little oil in the filter itself but most of it had settled in the bottom of the pan.

[benno_84]

To Ynot,

Thanks for the advice Tony, and the thread link. I was going to give the valves a go after all the fluid changes. I have never done them before so am a little nervous to be honest. I might try and do it over a beer with a mate who knows what he is doing.

Would you mind just explaining what PCV actually is and what causes it? So far I have gathered that the turbo creates some sort of back pressure in the top of the engine which if not released can cause damage, so basically there is a valve called a blow by valve which provides release of this pressure. Given that there is oil in the top of the case it gets forced up the valve and into the air filter housing. Is this it? Fill me in please as all this stuff is fairly new to me (first time 4wd owner).

Lloyd

[YNOT]

Blow by is present in all piston engines to varying degree's. It's caused by combustion gasses leaking past the piston rings into the crank case, as an engine wears the amount of blow by will increase. With all that hot oil being thrown around inside an engine while it's running there is also an amount of oil mist inside the engine cavities.
The blow by gases need to be vented to stop pressure build up in the crank case (Positive Crankcase Ventilation), any pressure build up would push oil past seals and gaskets. But to just put a vent in the rocker cover would allow oil mist to escape with the gases, creating a unwelcome emission to the atmosphere. This is where recirculating PCV systems come in. By running a hose from the top of the rocker cover back to the air inlet, the oil mist and blow by can be drawn back into the engine to be burnt.
The downside to drawing oil mist back into the engine, is that it coats everything in the air inlet with oil. This oil coating is not normally an issue, but it reduces the effiency of intercoolers, and can leak out if it finds a spot that's not properly sealed. That's why people like myself have started fitting PCV filters to filter out the oil while still allowing the blow by gasses to be drawn back into the engine.
For owners of vehicles with Mass Air Flow (MAF) sensors, if the oil mist is not filtered out, it can after engine shut down, travel back up the air inlet and coat the MAF sensor. This can cause the sensor to incorrectly read the air flow and send false signals to the engine computer. A MAJOR cause of ZD30 engine failure.

Tony

[benno_84]

To YNOT

Thanks for all the information mate. That makes alot of sense. I am not to worried about a little oil in my airfilter if it is normal. I guess it probably acts a little bit like a wet filter does in a motor bike anyway (makes the dirt stick to it). I might have a look into the PCV filters anyway just for interest sake. Where do you get them from? Are they easily installed? Is a PCV filter essentially the same thing as a catch can?

I dropped the oil out of the rig the yesterday and changed all the filters so I am nearly ready now to move onto the suspension and possibly those valve clearances you suggested.

Lloyd

[YNOT]

Catch cans and PCV filters are much the same. I did a lot of research before I got mine, a lot of people have tried a lot of different filters and CC's, the one that stood out as having the most consistant good results was the Mann-Hummel Provent 200.

http://i758.photobucket.com/albums/xx224/tonyh01/HBGCLRica_a.jpg

I've been very happy with mine. Have a look on EBAY or your local filter supplier, cost is about $200 plus about $50 for hoses and adaptors to fit it.
They are easy to fit, you basically just extend the hose from the rocker cover to the air inlet, and divert it through the filter. The Provent 200 has the abillity to be plumbed to automatically drain back to the sump, but most people just put a length of 1/2 inch hose off the bottom of the filter with a drain tap in the end of it. Just drain the collected oil out every 5000km or so.

http://i758.photobucket.com/albums/xx224/tonyh01/P1000707Medium.jpg

Here's a pic of mine fitted, mines a ZD30 but fitting is much the same.

Tony

[Finly Owner]

Blow by is present in all piston engines to varying degree's. It's caused by combustion gasses leaking past the piston rings into the crank case, as an engine wears the amount of blow by will increase. With all that hot oil being thrown around inside an engine while it's running there is also an amount of oil mist inside the engine cavities.
The blow by gases need to be vented to stop pressure build up in the crank case (Positive Crankcase Ventilation), any pressure build up would push oil past seals and gaskets. But to just put a vent in the rocker cover would allow oil mist to escape with the gases, creating a unwelcome emission to the atmosphere. This is where recirculating PCV systems come in. By running a hose from the top of the rocker cover back to the air inlet, the oil mist and blow by can be drawn back into the engine to be burnt.
The downside to drawing oil mist back into the engine, is that it coats everything in the air inlet with oil. This oil coating is not normally an issue, but it reduces the effiency of intercoolers, and can leak out if it finds a spot that's not properly sealed. That's why people like myself have started fitting PCV filters to filter out the oil while still allowing the blow by gasses to be drawn back into the engine.
For owners of vehicles with Mass Air Flow (MAF) sensors, if the oil mist is not filtered out, it can after engine shut down, travel back up the air inlet and coat the MAF sensor. This can cause the sensor to incorrectly read the air flow and send false signals to the engine computer. A MAJOR cause of ZD30 engine failure.

Tonyanother one for ynots file