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Disappearing Oil. I'm out of ideas....91 TBI 350

Can the blue smoke be totally covered up by the catalytic converter?

I'm really struggling with the idea that I'm burning a quart of oil every 300 miles and there is nothing visible from my tailpipe when I start the truck, or while it is idling in the driveway or while I drive (that I can see).

I had a bad oil burning truck before and I was making a nice blue cloud behind me all the time that I could easily see while driving. Other cars would swerve to avoid it.:D
 
Aliens are coming down in the middle of the night and stealing it to use for cooking up their foods.
 
Oil has to go somewhere, pull the plugs, you've probably driven it enough now to be able to see fresh oil on them.

Mine didn't burn THAT much oil, but it did burn through some and I never saw any smoke really either, now and then I'd see some mainly during acceleration from stopping.
 
80' 427 said:
intake gasket
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I've come across mention of intake manifold when googling for oil consumption but I didn't know oil went through the intake? I thought only coolant went through the intake manifold?:confused:

Can you provide a bit more detail on this possibility? Thanks!
 
4xcrazy said:
Oil has to go somewhere, pull the plugs, you've probably driven it enough now to be able to see fresh oil on them.

Mine didn't burn THAT much oil, but it did burn through some and I never saw any smoke really either, now and then I'd see some mainly during acceleration from stopping.
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4x...Is there a spark plug that is most vulnerable to oil from valve seals or most likely to be oiled up that I could pull so I don't have to pull them all? Thanks!
 
I think the rear plugs are more susceptible as the engine is slightly tilted to the rear. So pop off the drivers side rear and see whatcha got...
 
Thanks Jessie, will do that as soon as I get a chance which might be a few days...I suppose it isn't that big a deal to pull them all if I have to, I'll get photos too.

*****Edit: here it is (see next page for more photos)*****
402982470.jpg
 
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Anything funny going on in the radiator? Oiliness?- water disapearing? Leaking?

And What kinda oil is being used? Buddy had an 89 burb that would smoke just a bit when on the freeway... Used a fair amount of oil... Previous owner kept adding and adding...
LT1 swapped into that truck, and years later i bought the smokey motor to rebuild. It had a HUGE problem with sludge. I mean 1/2 inch thick throughout most areas it could cling to. Could not even see the lifters when i pulled the intake- just burried in there somewhere. Guy that i got the motor from was a reputable mechanic and claimed penzoil did that (and previous owner only used penzoil). Rings were just about gone in that motor, and the bore had to be cut 60 thousandths... Had about 60k miles on it since it left the factory...
Not sure if i have any basis to be so affraid of penzoil, but im affraid to use penzoil LOL... Not sure if there were other problems that caused that, but wow.
 
Big6ft6 said:
I've come across mention of intake manifold when googling for oil consumption but I didn't know oil went through the intake? I thought only coolant went through the intake manifold?:confused:

Can you provide a bit more detail on this possibility? Thanks!
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If the intake gaskets are leaking it can pull oil from the lifter valley.
 
scouthead said:
Anything funny going on in the radiator? Oiliness?- water disapearing? Leaking?

And What kinda oil is being used? Buddy had an 89 burb that would smoke just a bit when on the freeway... Used a fair amount of oil... Previous owner kept adding and adding...
LT1 swapped into that truck, and years later i bought the smokey motor to rebuild. It had a HUGE problem with sludge. I mean 1/2 inch thick throughout most areas it could cling to. Could not even see the lifters when i pulled the intake- just burried in there somewhere. Guy that i got the motor from was a reputable mechanic and claimed penzoil did that (and previous owner only used penzoil). Rings were just about gone in that motor, and the bore had to be cut 60 thousandths... Had about 60k miles on it since it left the factory...
Not sure if i have any basis to be so affraid of penzoil, but im affraid to use penzoil LOL... Not sure if there were other problems that caused that, but wow.
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Haven't noticed anything in the radiator, that was one of my first guesses since this truck has the engine oil cooler in the driver's-side radiator tank. To be safe (and rule out a cooler line leak) I pulled the engine oil cooler.

It looks clean under the valve covers (as far as sludge goes), I have no idea what type of oil has been used in it previously I've only had the truck for 600 miles or so, but since I've been going through a qt every 300 mi, I've just been tossing in cheap walmart stuff until I can get it figured out.
 
ChrisPerry said:
If the intake gaskets are leaking it can pull oil from the lifter valley.
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Ah ha...that makes sense. Thanks. I dont know how to test for that. It seems if I'm going to do anything, the valve stem seals are what to do first. Even if they aren't the main problem, at this mileage, they're likely contributing. Still haven't had a chance to call to get a quote on that work, I'm not even sure when I'll have time to get it in there.
 
So driver's slide plug is clean...looks just like it did after I'd had the truck for 300mi. Now I've driven it 600+ miles, didn't pull the rest since they all looked the same at 300mi, I assume they all look the same now too.
402982470.jpg

Here is what things look like inside the spacer between the throttle body and air cleaner where the fresh air hose goes into the driver's side valve cover.
402982467.jpg

Here is the back of the injector pod, the bowl containing fuel pressure regulator. This sits directly in front of where the breather hose pipes into the spacer.
402982464.jpg

Here is the sooty exhaust pipe
402982469.jpg
 
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So just talked with my mechanic. From listening to my story he thinks the oil rings are stuck and not scraping the oil off the cylinder walls. He says the oil burning is happening most once the oil heats up and is thin the oil burns fairly clean so it doesn't foul plugs and by the time oil heats up the catalytic converter is also hot and will conceal oil smoke.

He said if it was valve seals, I would see oil smoke at start up because oil would have dripped into the cylinders at the end of the last drive, and the catalytic converter would be cold at start up so you would see a blue plume at the tail pipe.

His recommendation, put a quart of tranny fluid in with the oil and drive it for 500mi. He says tranny fluid has VERY high detergents and maintains a bit of the lubricity of oil. Then drain it out and replace with fresh oil.

He says it works just like sea foam and other "tune-ups" in a bottle but it is cheaper. Not guaranteed to do anything, but he said it is worth a shot, they've had some success with this on junk-yard motors freeing up oil rings. He said they also use it when they pull a cylinder head, if a piston has hard carbon build up, they pour a bit of tranny fluid on the piston over night, and in the morning they can literally wipe the carbon off the piston with a towel.

It'll take me a while to drive 500mi, but I'll report back how it works.
 
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So here is my new theory.

This truck was operated for a long time with a stuck PCV valve. This caused bad sludge problems in the lower engine and caused oil to be blow/sucked up through the vent hose into the throttle body causing the sludge on the throttle body that you see in my photos above.

Now I'm dealing with the consequences and stuck oil rings and who knows what else. Can't prove this is what happened, but evidence seems to point that way.
 
big pappa b said:
Here's an article on doing that:

http://bangshift.com/blog/driveway-...eeing-stuck-piston-rings-did-we-succceed.html
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The first part of the article was great! The conclusion sucked:pimp:

I'm still holding out hope, I don't have anywhere near the problem with smoke that these guys seemed to have (although no catalytic converter on the 73 monte).

But the story sounds almost exactly like my situation. The truck is in great shape but likely sat a lot and had short trips (20k miles in 8 years from the previous "old man" owner!). Everything else about the truck suggests excellent care and an easy life, but short trips, and I think a one-time clogged PCV, might be behind my oil consumption.
 
well one way also would be to remove the hose going into the spacer, and putting an extension to it and drop it below the engine.
And plug the spacer hole, that will put less pressure from the return hose, you end up with less oil consumption and less gas consumption, but since it doesn't go into the CAT anymore you might see white or blue smoke coming out of this tube.
I did that on lots of engines before and got a few more years out of them.
 
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