blow by advice needed

[canucksafari]

Hijack - seeing Mat has his answers and Dougal started talking about burning oil and valve stem seals.

I have often wondered what causes a diesel engine to burn a little bit of oil after it has come down a long grade on engine compression. It seem to always occur just at the base of the grade as soon as you give it a little fuel. All the way down, there hasn't been any noticeable oil burning. The driver then gives it some fuel and a puff of blue smoke comes out the exhaust. I don't think it is leaky valve stem seals, as on the vehicles I have never noticed smoke after them sitting and idling. I have noticed this following a BJ73/74 and an HJ81. I have also noticed it once on my TD4.2 after a long, but quick, decent from 5500' to about 1500'.

 

[cruisedeisel]

i think that problem might be the bearing/seal between the the two turbines on the turbo but not for sure. my friend had similar problems when his turbo was going down. but far worse smoke. The bearing was the problem.

 

[canucksafari]

That could explain the two turboed engines but the TD4.2 is NA. AFAIK, neither engines have had the turbos rebuilt and this was a couple years ago.

 

[Dougal]

That could explain the two turboed engines but the TD4.2 is NA. AFAIK, neither engines have had the turbos rebuilt and this was a couple years ago.

I think it's simply combuston not hot enough to burn oil from the breather/rings completely. EGT's downhill are usually sub 100C so the oil builds up, first application of power is enough to burn the oil to blue smoke but not yet hot enough to burn it cleanly.

 

[BC40]

that's the type of info I was looking for. Thanks guys! It does make sense that at lower pressure and slow cranking the wear wouldn't be as noticeable, where at 2400RPM and 12+PSI on top of the regular compression I could see some slop.
I'll do some more test over the next few months if I find something interesting I'll let you know.

thanks guys, its pointing me in the right way. a rebuild 4 sure this summer.

HEY FANTOM, do you have hard starts too?

That was just my best guess, so definitely do more testing before doing anything drastic. Mat, that was what I was getting at in your other thread, when I mentioned it could be linked to how your truck seemed to have lost some of its power output after you'd run the turbo a while, then shortly afterward you saw the blowby increased. Really as long as the compression is there for starting and power is ok, I'd just run it.

 

[Fantom]

I've been playing (before this) with some things and managed to get a little more power (removing the 2 33" tires off the roof helped a lot - which I knew they would). I am still running it a little cool on EGTs, I don't want to turn the fuel up too much in the winter and notice that I'm over 1200 in the summer. So right now the power thing I'm ok with.
I will do more tests, especially before I tear anything apart.

Cruisedeisel - I do have hard, cold starts but the truck has had that issue ever since I got it (way before the turbo). Any time the temperature drops below 5C I have to gow the plugs (manual) 10 seconds. If it drops below 0 I have to do it for 20 seconds for it to fire up without shaking itself to pieces. Always been an issue that I could never solve. Changed the injectors, changed the glow plugs, the fuel system does not have any leaks (that I have ever been able to find) so I just gave up on trying to figure that out. Why do you ask?

 

[Fantom]

Turbos push air and exhaust into the crankcase through their oil drain, if your breather is struggling to keep up the extra flow from the turbo could push it over the edge.

Are your valve seals okay? The only time my diesel has ever used oil the valve guides and seals were leaking oil into the intake and exhaust ports. In my experience even low compression on a diesel won't make it burn oil in the same way a petrol engine does.

Even new turbos push air and exhaust into the oil return? the seals around the turbine shaft should stop that from happening? I know mine has several on both sides. When you refer to the breather struggling to keep up, which breather are you referring to?
Valve seals are likely going, the engine does have 533,000+ kms on it so I would bet they are not perfect. Last time I did a leak down test I know the exhaust valves were letting air by.

 

[Dougal]

Even new turbos push air and exhaust into the oil return? the seals around the turbine shaft should stop that from happening? I know mine has several on both sides. When you refer to the breather struggling to keep up, which breather are you referring to?
Valve seals are likely going, the engine does have 533,000+ kms on it so I would bet they are not perfect. Last time I did a leak down test I know the exhaust valves were letting air by.

The seals on a turbo are like piston rings, they aren't a complete mechanical seal, instead a labyrinth which still passes a small amount of air. As the turbo gets older and wears the pass more gas and contribute more to blowby. The breather I mentioned is the engines breather from crankcase (or rocker cover) to either outside or vented back into the intake. This is the only escape for any gas that builds up in the crank case.

How much wiggle do you get from a valve stem? Might be time to pull the rocker cover and take a close look.

 

[Fantom]

the valves have been adjusted about 3 months ago and are tight, although I don't know the status of the seals. The 3B does not have a Valve Cover (rocker cover) breather. If that is the case it would apply the boost pressure to the oil system, since the only breather the oil system has is the blow by tube it would push more oil out that way. With that said you should see an increase in Oil Pressure as you have an increase in Turbo Boost. Since I have not noticed this I don't think this is the case. Unless I'm still missing something.

 

[cruiser_guy]

the valves have been adjusted about 3 months ago and are tight, although I don't know the status of the seals. The 3B does not have a Valve Cover (rocker cover) breather. If that is the case it would apply the boost pressure to the oil system, since the only breather the oil system has is the blow by tube it would push more oil out that way. With that said you should see an increase in Oil Pressure as you have an increase in Turbo Boost. Since I have not noticed this I don't think this is the case. Unless I'm still missing something.

I doubt you'd see much of an oil pressure increase from increased boost. First of all the oil pressures are far more than we'll ever see on the turbo so a 5psi increase in boost pressure likely wouldn't even move the oil pressure gauge needle. It's all about the scale on the meter. Turbo will be 0-20psi more or less, oil pressure 0-150psi more or less.

 

[canucksafari]

I think it's simply combuston not hot enough to burn oil from the breather/rings completely. EGT's downhill are usually sub 100C so the oil builds up, first application of power is enough to burn the oil to blue smoke but not yet hot enough to burn it cleanly.

That makes sense. Also, each time this was observed on a cold fall day.

Hijack out.

 

[Fantom]

I doubt you'd see much of an oil pressure increase from increased boost. First of all the oil pressures are far more than we'll ever see on the turbo so a 5psi increase in boost pressure likely wouldn't even move the oil pressure gauge needle. It's all about the scale on the meter. Turbo will be 0-20psi more or less, oil pressure 0-150psi more or less.

Actually the oil pressure sits at about 50-60 on the highway, and the guage I have would show a 5PSI increase and decrease, which I am not seeing. Maybe I would it I located the pressure sensor in a different spot it would change readings. I'll have a look at the turbo to see if there is any oil getting into the exhaust of intake sides, if air is getting by then oil might be too.

 

[Dougal]

the valves have been adjusted about 3 months ago and are tight, although I don't know the status of the seals. The 3B does not have a Valve Cover (rocker cover) breather. If that is the case it would apply the boost pressure to the oil system, since the only breather the oil system has is the blow by tube it would push more oil out that way. With that said you should see an increase in Oil Pressure as you have an increase in Turbo Boost. Since I have not noticed this I don't think this is the case. Unless I'm still missing something.

The rocker cover and the crankcase are the same enclosed space, an engine can have the breather anywhere on the crankcase or rocker cover and it does the same job. Where-abouts is it on the 3B?

 

[Fantom]

I don't think the 3B has one, that's probably the reason why it vents into the atmosphere via the blow by tube. In later engines that chamber was routed back into the valve cover and intake system for emissions reasons. This engine was built before all that stuff kicked in and is therefore much simpler with less crap on it.

 

[Dougal]

I don't think the 3B has one, that's probably the reason why it vents into the atmosphere via the blow by tube. In later engines that chamber was routed back into the valve cover and intake system for emissions reasons. This engine was built before all that stuff kicked in and is therefore much simpler with less **** on it.

The breather is the blow-by-tube. Same thing, different names. Where is is venting from and how big is it?

 

[VTCDN]

It was called a Draft Tube , Way back when ,,,, was phased out in the early 60's in Gassers.
A few of my cars had them , plus some quirky items also.

3B has it's draft tube on the lifter galley cover, inside is a basic oil trap / oil deflection system/covers.14mm tube size 25cm long and lubes the front U-joint well .

Crankcase internal pressure is oil pan /under valve cover area.OIL PRESSURE is after oil pump through filter to the bearings and cyl head rocker shaft, fuel injection pump and the oil piston squirters.

Like one is your blood pressure (oil), and the other is your lungs, there NOT connected pressure wise.

Max oil pressure is limited by the max oil relief valve in the front timing cover , Min pressure is from wear.

For having high crank case pressure and 500kms , Just internet dart throwing I'm going worn rings .
Valve guides worn that much is a stretch..

On My 3B i'm installing a real Oil trap / "Breather" as some call them.
This will be vented to the inlet compressor turbo .

Another crankcase venting extraction system was the headers drafting used on some fancy sport cars, This was when we all smoked & had hair.

VT

 

[lostmarbles]

......
Crankcase internal pressure is oil pan /under valve cover area.OIL PRESSURE is after oil pump through filter to the bearings and cyl head rocker shaft, fuel injection pump and the oil piston squirters.

Like one is your blood pressure (oil), and the other is your lungs, there NOT connected pressure wise.......
VT

Increase your crankcase pressure by 5psi and your oil gauge will automatically read 5psi higher VT..... (even though your true oil pressure hasn't really risen).

True oil pressure = "gauge pressure minus crankcase pressure" but you can normally ignore the crankcase pressure because it is normally "atmospheric pressure" which is normally taken as being zero (as far as pressure gauges are concerned).

 

[VTCDN]

True Lostmarbles .
BUT !! A 5psig Crank pressure will have seals pissing all over.
Modern engines run a small negative of atmospheric pressure , or should ..
I have 2 different test gauges just for that, If i see fuel trims either way , do that test first, EZ and no amount of any fuel monitoring part will get trims back into range. A crankcase pressure variance
of + or - in major amounts has caused tech's to be parts throwers.

So if I was to see an real Oil pressure gauge read different from a crankcase pressure , thats also stretch. In theory because the gauge is using outside of the engine as it reference of ambient pressure .

If it was 5 PSIg internal crank pressure, and IF the front and rear crank could hold back the pressure without popping out , then the Draft tube would become a blast oil spreader, and the front drive shaft all the Way back and under would be coated with oil.

Just for giggles, Ill patch in one of my crankcase measuring units on the 3B, NA model and see..

I need to go into the village later today.

VT

 

[Dougal]

What Lostmarbles means is the oil pump is both picking up and delivering oil within the crankcase. So any pressure in the crankcase will add to the total pressure of the oil circuit.

You're correct that the gauge is outside the crankcase and will only read the pressure within, but the pressure it is reading is case pressure + oil pressure.

 

[crushers]

holy crap, you have 8L of oil in there and you are concerned about a liter drop over 5000 km?
worry wart.

budget a rebuild for when you start really going through the oil, till then lighten up.

but

keep an eye on it.