Missing oil mystery?

[amaurer]

Well, I haven't noticed any smoke, but I do smell something from time to time (its tough to me to choose between diesel exhaust and burning oil). When I use the engine to brake, like when coasting down a hill without pressing the clutch, I smell "something" the most; someone told me that means you need valve seals.

I'm really at a loss to find where all this went, its frustrating.

 

[crushers]

are you SURE it was topped up properly at the beginning of the test?

 

[amaurer]

are you SURE it was topped up properly at the beginning of the test?

No. I'm checking it daily now trying to establish a baseline. I'll have 200km's by Tuesday of next week, maybe I'll see something.

 

[Granite Grinder]

Correct me if I'm wrong (happens all the time)
If your oil rings are worn, you'd see blue smoke from the tail pipe.
If your valve guides are worn, you'd see smoke in the form of blow by... might show up from the breather tube or if you opened up the oil filler cap it would be coming from there?
GG

 

[amaurer]

I don't think so, the valve guide seals the valve stem, which passes through the intake/exhaust channel, not the combustion chamber. Any blowby would have to sneak around the (closed) valve itself, through the intake/exhaust channel and out of the seal... i kinda doubt that.

 

[crushers]

blow by is the excessive pressure that can be built up in the oil system (not related to oil pressure)... i.e. oil pan, rocker cover area etc
so worn oil rings can let combustion pressure leak past into the oil pan area and thus pressurizing the rocker area and the blow by, since there should be no pressure in this area (other than that created by moving parts.
worn oil rings and worn valve seals and valve guides allow oil into the combustion chamber there is evidence of blue smoke.

make any sense?

 

[RufusTheDufus]

When I use the engine to brake, like when coasting down a hill without pressing the clutch, I smell "something" the most; someone told me that means you need valve seals.

The 3B in my BJ42 does the same thing. I know I need new rings. My compression numbers are very low so I put a leak down tester on it which confirmed it's the rings.

I go through what I consider to be a lot of oil. 1 quart every 500 to 700 miles depending on altitude and load. Most of that goes right out the breather tube in the form of oil vapor, much of it ends up coating the underside of the vehicle.

My uneducated guess about the smell being stronger on deceleration is the throttle plate. Take your foot off the pedal when the engine is spinning faster than idle and it's going to create vacuum in the intake tract and combustion chambers. If you've got bad rings and/or valve seals the vacuum generated is going to suck oil past them into the combustion chamber.

I really noticed a difference in smell when I took the top off this year. There's a noticible difference in the smell of dino oil and synthetic too.

 

[RufusTheDufus]

BTW, have you tried to get a friend to follow you to watch your exhaust color? Mine puffs blue only on deceleration. It's not enough blue smoke to see from the driver's seat though.

Do you get blue smoke at startup? That would be the most common indicator of bad valve seals.

 

[lostmarbles]

My 2c .... As I see it..........

The exhaust valves run far hotter than the intake valves - so wear on their stems and seals occurs faster. Thus, when you have "worn VALVE seals/guides/stems", the symptoms are normally caused by oil from the rocker-cover area (top of engine) dribbling down the exhaust valve stems/guides into the exhaust ports. This is seen as blue smoke -

• On start-up after the vehicle has been left sitting for a while (where the oil has had time to dribble into the exhaust ports and accumulated there), and
• When you first apply power again after "engine-braking down a long gradient" (where again, the oil has dribbled down the exhaust valve guides/stems). - But this time, because oil is still being continuously pumped into the rocker-area, there is usually a greater amount of oil that has accumulated in the exhaust before you hit the accelerator to burn it - So the smoke cloud should be more noticeable in this test/scenario.

Now if you have worn compression rings, this allows combustion gases to escape into the crankcase on each cylinder's ignition/explosion (rather than being contained in the combustion chambers). This abnormal flow of gas, if it becomes high enough, will carry oil droplets with it. And an engine must be "vented" to prevent this "gas leakage" from pressurizing the engine crankcase (and thereby prevent any pressure build-up from blowing out the crankshaft oil seals). Mine has a "breather/blow-by tube" that exits above my front driveshaft. So this tube will cover my front driveshaft with engine-oil if my compression rings are badly worn. Other engines may have the blow-by routed into their air-intake - Here excessive blow-by (and consequent oil-carry-over) will result in blue smoke from the exhaust whenever you apply power (- as that oil passes through the engine and gets burnt).

Now - to have oil-loss caused by "worn oil rings alone" (while your engine still has good compression on all cylinders) - Well - I'm not sure that is likely/possible. --- Is it? (Rare enough to be ignored?)

So - as you have good compression figures Drew - I would think leakage from seals/gaskets is the likely culprit - and that perhaps you are mistaken about the magnitude of your oil-loss.

And I doubt you have a valve guide/seal/stem problems because I would expect you to have noticed the significant smoke that would have generated.



PS. I know I'm repeating what's already been explained by others. But I thought there was a need to throw it all in one post.

 

[amaurer]

Good advice, and summary Tom.

A lot of my symptoms are contradictory...

-No smoke, at any time. Not even at startup after a long sit. Its warm here in the mornings (low 60's F) so that helps, but I haven't noticed anything blueish.

-Stinkiness when decell'ing.

-Good compression, but I do have blowby. I run a catch can to stop the occasional drip. (brain bender, I know)

I'm watching the oil level daily, I'll try to get a good number.

 

[lostmarbles]

.... but I do have blowby. I run a catch can to stop the occasional drip. ....

I have blowby too Drew. And my front driveshaft is always "wet" with oil. But where I park in our concrete driveway has no oil stains whatsoever. So that's the guide I go by that things are really OK for me.

Ps. - Under Sandy's (my wife's) car is a diiferent story. There's a real oil slick there!

Also, lately I've been starting up the cruiser and leaving it running for a while in the driveway. (I know - I'm "a neighbour-from-hell.) And when I come back to it I sometimes smell that unpleasant "blowby smell" as I walk alongside the vehicle.

By the way - I will get aound to doing "compression" and "leakage" tests and I've got the "Harbor Freight" gear (compression tester exactly the same as yours) ready for it. Thanks for putting me onto that source - because there's no point in my going for expensive gear when it will see little use.

It is just that I'm majorly sidetracked at the moment. ----- Sandy has insisted on a new stove/oven in the kitchen and yours truly is during all the install/modifications work there.

 

[amaurer]

Based on what I can see so far, it seems the oil loss is "real"

I topped it off on the 9th and I pulled the stick first thing in the morning on the 11th, 13th, and today:

s***.

 

[crushers]

try it again for the next few days...
make sure you are on the same level spot when you check and the engine at the same temp (i.e. not cold verse just running)

that last drop seems irrelevant..

 

[amaurer]

try it again for the next few days...
make sure you are on the same level spot when you check and the engine at the same temp (i.e. not cold verse just running)

that last drop seems irrelevant..

Yep, been checking in the garage, mornings only before driving. I've got a long drive tonight and will keep checking it.

 

[amaurer]

I put 75 highway miles on yesterday, sure enough, its dropped a little more...

 

[crushers]

deffinately looks like your eating the oil but you say no smoke...
how big is the puddle from the blow by tube recently?
is the front of the engine any "wetter" since you last looked?

you should not be going through that much oil that quick...agreed.

 

[RufusTheDufus]

When was the last compression check?

 

[amaurer]

deffinately looks like your eating the oil but you say no smoke...
how big is the puddle from the blow by tube recently?
is the front of the engine any "wetter" since you last looked?

you should not be going through that much oil that quick...agreed.

I keep watching for blue smoke but I've never seen any. It certainly doesn't puff blue when its sitting still, as I've gotten out and tried several RPM's with the hand throttle but see nothing.

It doesn't leave any drips on the garage floor. I have a catch can on the breather because once upon a time it would leave a single droplet each day. The catch can is largely empty, I've never emptied it and it has less than a few mL in it.

The engine is wet with oil, from the valve cover (which I haven't torqued fully because I cracked it, doh), side cover, pan gasket, and front main seal area. However none of it seems to be enough to drip, which makes me think I'm not leaking it away.

When was the last compression check?

A month or so, maybe two? Compression was good 395's average. That makes me thing the oil rings are OK too, but hell, what do I know...?

EDIT: I should add that I don't think I was losing oil when I bought the truck. The first thing I did was drive the 400 miles from LA to cupertino without using a noticable amount.

 

[eleblanc]

I remember on a post i did, i mention the maximum allowable pressure in inch of water that you should read throught the oil dip stick.

I was told to remove the oil dip stick, put a small rubber hose in the dip stick hole, long enough to be able to read pressure in the truck while you are driving. Surely at the other end of the hose (in the truck) connect a dwyer gage that read 0-10 Water G (inchs of water).

Unfortunately i don't remember the pressure not to exceed. Search my nick and "pressure" you might find it on the forum.

This test will tell you if your rings are due. basicly it tells you the pressue in the crank case.

I personnaly never did the test. I do have some blowby and the front drive shaft is always wet, but i do not loose oil like you do, at least not has much.

Also, if you run a catch can, and the vent on the catch can is not big enough, this may cause back pressure. So what should be coming out from the crank case vent is not and going else where. Therefore you wouldn't be noticing serious oil leak from crankcase vent.

 

[amaurer]

I remember on a post i did, i mention the maximum allowable pressure in inch of water that you should read throught the oil dip stick.

I was told to remove the oil dip stick, put a small rubber hose in the dip stick hole, long enough to be able to read pressure in the truck while you are driving. Surely at the other end of the hose (in the truck) connect a dwyer gage that read 0-10 Water G (inchs of water).

Unfortunately i don't remember the pressure not to exceed. Search my nick and "pressure" you might find it on the forum.

This test will tell you if your rings are due. basicly it tells you the pressue in the crank case.

I personnaly never did the test. I do have some blowby and the front drive shaft is always wet, but i do not loose oil like you do, at least not has much.

Also, if you run a catch can, and the vent on the catch can is not big enough, this may cause back pressure. So what should be coming out from the crank case vent is not and going else where. Therefore you wouldn't be noticing serious oil leak from crankcase vent.

The crankcase pressure test measures the health of the compression rings... which I already did directly with the compression test. I do have some blowby, however.

My catch can vent is big enough, I actually made that mistake and suqeezed some oil out from, well, everywhere. Now its simply a can clamped to the breather, the top is wide open.