My Diesel Let me down!

[smithy010]

Hi All,

I was on my way 600km to Narrandera from sydney, when my old girl let me down last night.

I got 100km down the road, and she started running on, and overheating.

I stopped at pheasants nest, topped up the oil, let her cool down, checked the air filter (the manifold had a lot of oil in it, as expected).

I carried on for 20k's (after calling aydan), and she started doing it again. I tried taking the air filter out, but that only created a ****load of smoke because the air filter housing was leaking oil onto the exhaust manifold. So i stopped, rang the old man and said i wouldn't be home that night.
I decide i would limp her home, so i made a catch can (may as well not have).

My car went through 4L of oil (poured it on the ground) on the way back home.

Now i'm trying to diagnose what's wrong. What i don't understand is, why all of a sudden am i having all this blowby?
Have i cracked a ring or something?

Or have i done a valve seal or something like that?

[smithy010]

Oh, and for everyone's information, once it stopped running on, by the catch-can method, the temperature behaved itself quite well, and it ran very well. Smooth as ever.
It also starts very easily.

I don't really believe that there would be anything wrong with the piston/rings, because it would surely be running rougher than before.

The sudden-ness of it all is what confuses me.

But there is definitely some serious positive pressure coming from the tappet cover.

I have the blowby stopper, but with this amount of oil, it didn't help at all.

Please tell me it's something i can fix without taking the head off!

[Greg Roles]

I'm afraid my vote is for a leaking valve seat. Explains the increase in pressure from combustion into oil jacket, thus pumping oil out the crancase vent. Fraid that means the head off mate...

I'm not a diesel guru, so how the heck do you check combustion pressures without sparkplug holes? Pull the injectors?? Anyone??

[cetane]

Compression tests are done through the glow plug hole with the fuel solenoid disconnected and at full throttle.
Sorry, Smithy...It doesn't look good. For that much oil going into the air box it has to be more than just rings. Do you have the VW modified breather?

[gregozedobe]

Compression tests are done through the glow plug hole with the fuel solenoid disconnected and at full throttle.

Just curious - why full throttle on a diesel ? (on a petrol engine yes, but from my understanding of a diesel the accelerator pedal only controls the amount of fuel injected)

[cetane]

Ooops..Been thinking of my Nissan SD33 a bit too much lately! (It has a multi-element injection pump with a butterfly to control inlet air). No...full throttle isn't necessary with a distributor type pump such as the VE.

[gregozedobe]

Well there you go, keep your eyes open, your ears connected, your brain connected and you can always learn something new

[gldgti]

hey smithy,

this is an old time issue that comes up again and again.

i know it seems to be "all of a sudden" but this type of thing occurs when you get the oil really nice and hot - on the highway - and under sustained high rev conditions - highway. unless you have both of these its hard to get to a runaway condition.

the continued high reving allows good buildup of oil fumes to occur, since you have low load conditions and high revs, a nice production of oil vapours will occur and then you know the rest.

get rid of the 10W-40 for some heavier oil, and get ready for an engine pull-down.

basically mate you need to pull her down and do the rings. seriously.

good luck,
aydan

[smithy010]

Well...

It actually does seem sudden, because just last weekend i took it on a hard run up the blue mountains- Got the oil nice and hot up the mountain, then on the relative flats and downs of the bells line, i had her at high revs and there was not even a hint of anything wrong. Up there and back, and 110 on the great western highway and nothing. Then this just a week later. I think something must've happened suddenly.

What i also don't understand, which i took for granted before, was that i am now getting high tappet cover pressure.. Wouldn't bad rings cause high crankcase pressure, and not high tappet cover pressure? Can someone explain to me how the pressure is getting to the tappet cover?

Oh, and i'm sure the high pressure is coming from the top of the engine.

Another theory is that i've done a head gasket, and the pressure is coming up through an oil gallery.

Ok. Next question.

If it turns out i need to re-ring her.. Then assuming it is so bad that i need pistons as well, how much will i be up for, and am i better off hitting loon up for one of those 1Z engines that he's got coming?

[Preen59]

Well...

It actually does seem sudden, because just last weekend i took it on a hard run up the blue mountains- Got the oil nice and hot up the mountain, then on the relative flats and downs of the bells line, i had her at high revs and there was not even a hint of anything wrong. Up there and back, and 110 on the great western highway and nothing. Then this just a week later. I think something must've happened suddenly.

What i also don't understand, which i took for granted before, was that i am now getting high tappet cover pressure.. Wouldn't bad rings cause high crankcase pressure, and not high tappet cover pressure? Can someone explain to me how the pressure is getting to the tappet cover?

Oh, and i'm sure the high pressure is coming from the top of the engine.

Another theory is that i've done a head gasket, and the pressure is coming up through an oil gallery.

Ok. Next question.

If it turns out i need to re-ring her.. Then assuming it is so bad that i need pistons as well, how much will i be up for, and am i better off hitting loon up for one of those 1Z engines that he's got coming?

Crank case pressure is only vented through the cam cover breather. But it mainly comes from the crank case. You have ventilation around the cylinders that vents back up into the head (this is how some of the oil gets from the head back to the sump, too).

On some high performance engines you will see vents on both the crank case and the cam cover, but that is mainly to alleviate the additional pressure (the better you vent it, the less hp you lose). Whether the vent is in the block or the cam/tappet cover is mainly due to the application the engine will be used for and the components fitted.