burning oil

[72ZR1]

i think 1990 is going throw to much oil.it has 87,000 mi. i used 3qt. this summer and only put 1,500 miles on.and smells bad out the exhaust.runs great.any thoughts would be helpful. thanks.

[Polo-1]

90's do not have valve stem seals. They can be upgraded, and installed.

[Kevin]

the lt5 will use oil when run hard.

[tomtom72]

Not trying to be a wise guy....so take this as a fwiw.

I figure you have run down the list of the usual leak source suspects? It's true that the 90's don't have exhaust valve stem oil seals and if you drive enthuiastically you will have some loss from there. I assume that by 'smells bad from the tail pipes', you mean burning oil smell?....not gas from bad spray patterns causing wash down & loading up?

Just in case....
Header bolts in the center of the manifold go thru oil galleys.
CCVBox cover gasket & hoses. This was my biggest leak, it was enough to run out of the valley tube & stain the oil pan. It looked like an oil spill in the valley! You can see in thru the passenger side plenum runners to the valley floor.
Oil pan bolts....even the ones up front.
Oil cooler lines.
Oil senders. 2 of them.
PCV valves need to be in good shape along with the plumbing.Much oil can be ingested thru this avenue if the PCV's are not 100%.

If most of the above have been gone over and nothing too dramatic was found; then I suggest compression & leak down tests maybe the next diagnostic to run. Maybe even throw a vac gauge on her and see if it bounces alot, usually that could be bad guides but not always...then do the leak & comp tests. That's all I can think to check....sorry I'm still learning too. Oh, forgot....what's the plugs telling you about what's going on in the chambers!:redface:

Tom

[72ZR1]

thanks guys yes oil smell. no oil leaks.it burns oil when a don't drive it hard. I tryed just to see!

[tomtom72]

Okay I'm lost. :redface: You checked the plugs for signs of oil? The exhaust tips usually get fairly sooty, is it dry or wet? If there were a mechanical issue like rings or guides you would loose oil under load for sure and at light to moderate loads also....:icon_scra

Not to beat a dead horse.....you say you smell burnt oil, or burning oil...from where do you smell it? Standing at the exhaust tips you smell it? Or sitting in the driver's seat you smell it? Those exhaust bolts that leak will dump small amounts out on to the exhaust manifolds but usually it burns up before ever reaching the ground....so no tell tale spots in the parking space. If that motor used up 3 qts in 1500 miles.....something is amiss....I'm out of ideas, sorry.

[72ZR1]

smell is at the exhaust.and the tips are black hope to pull all the plugs this week

[72ZR1]

got the plugs out last night.7 of them like good but #4 plug had oil on it. tear down?

[tomtom72]

got the plugs out last night.7 of them like good but #4 plug had oil on it. tear down?


Okay, now we have something to work with. IMHO, if just one plug shows signs of oil in that chamber, I'd start with that cylinder and do a compression test and a leak down test. I would still put all the plugs back in and connect a vacuum gauge so I could see what the readings look like. Here is a link to reading and interperting vacuum gauge readings. http://www.secondchancegarage.com/public/186.cfm

I still can't see one cylinder eating that much oil by itself and the motor runs without a big miss due to an oil fouled plug....JMHO

Tom

[flyin ryan]

90's do not have valve stem seals.on the exhaust valves.

[blackjack]

generally speaking.an engine with a lot of mileage will show some oil deposit on more than one plug...i wouldnt be surprised to see a lower compression reading on that cylinder
bj

[HADI-ZR1]

oil leak in that chamber will give high comp. reading!!:o

technically, its wrong to say it gives low reading!

[tomtom72]

oil leak in that chamber will give high comp. reading!!:o

technically, its wrong to say it gives low reading!

Hadi, not exactly. You do the comp test by just spinning the motor say five times at each cylinder. The motor is off & you turn it by hand w/a breaker bar on the crank pulley. If you got a way low reading at any holes you would then squirt oil to see what affect that has on a re-test....in theory if the rings are that bad the PSI will go up with the oil shot.

That's why I kind of like to see what the vacuum gauge says before I do a comp. test....it kind of points you in a direction rather than starting off blind.

:thumbsup:
Tom

[HADI-ZR1]

Tom this is your opinion! :hello:
better make Leak Test to find out.

http://www.wcengineering.com/articles/ill/leakdown.jpg

[blackjack]

Hadi, not exactly. You do the comp test by just spinning the motor say five times at each cylinder. The motor is off & you turn it by hand w/a breaker bar on the crank pulley. If you got a way low reading at any holes you would then squirt oil to see what affect that has on a re-test....in theory if the rings are that bad the PSI will go up with the oil shot.

That's why I kind of like to see what the vacuum gauge says before I do a comp. test....it kind of points you in a direction rather than starting off blind.

:thumbsup:
Tom
thats what i meant...if you do a compression check when cold and you have more than,say,25% difference in that cylinder,you might have more serious problem than simply worn ring...i just didnt want to scare 72zr1;the fact that only one cylinder would be low is sometimes-did i say sometimes?-an indication that there is something wrong in that cylinder,other than normal wear...jmo
bj

[tomtom72]

Tom this is your opinion! :hello:
better make Leak Test to find out.

http://www.wcengineering.com/articles/ill/leakdown.jpg


:worship: You're correct it is JMHO. That's why I'm partial to using my vacuum gauge as it can help point you to the next logical diagnostic test....it's not fool proof by any means. I'm lazy and hooking up a vac gauge is easier than doing a comp test and a leak down test...:mrgreen: :redface: