Is it Blow-by?

[andrewjoelpeters]

As some of you already know, I've been trying to work on my '81 Tercel's (oil) smoking habit (212k miles). I thought I had it mostly figured out, but I've been fooled! As of now, I don't see any blue smoke on a short trip - even if I'm accelerating fairly hard. But when I drive the car thirty minutes or so, park it, and then drive it back home twenty minutes later, it'll start to smoke on hard acceleration on the drive home. And once it starts smoking, it doesn't stop much--even if I bring it down the revs--until the car has another chance to sit for a while. In a certain way, this sounds to me just like how I've heard blow-by described. But why would it occur only after the engine is warm?

A.J.

 

[Jeffs2006EvoIX]

Bad valve guide seals possibly?

Jeff

 

[Quest]

me thinks it's just a typical, worn/tired old engine that needs a complete overhaul.

Q.

 

[NateDN10]

When the engine is warm, the oil is warm, and it flows more easily. You're probably still burning oil when the engine is cold, just not as much.

 

[dishdude]

http://www.bobistheoilguy.com/blowby.html

Do you see compression gases coming out of the dipstick and oil fill hole? Sometimes it will blow the dipstick up out of it's tube.

 

[Cardenio327]

The oil return galleries might be plugged with sludge. After 30 minutes of driving it could be that it has pumped enough oil up to the head to start pooling around the valve guides.

 

[andrewjoelpeters]

Originally Posted By: NateDN10
When the engine is warm, the oil is warm, and it flows more easily. You're probably still burning oil when the engine is cold, just not as much.


Yeah, that's what I had been thinking, but the difference is pretty enormous. No visible blue smoke for a short trip, then all of the sudden lots for a longer trip.

Originally Posted By: Cardenio327
The oil return galleries might be plugged with sludge. After 30 minutes of driving it could be that it has pumped enough oil up to the head to start pooling around the valve guides.


I'm pretty intrigued about this idea--seems like it could make sense.

 

[Donald]

Have you pulled the valve cover to have a look around, check valve stem seals?

Compression test
add small amount of oil and another compression test

leakdown test?

When you burn oil, oil is getting from where it should be to where it should not be. It can do that by getting past the rings or valve stem seals. No other way into the combustion chamber.

Worn bearing can throw so much oil at the cylinder wall that the oil ring cannot scrape it off properly. The oil ring can be worn or gummed up/sticking and the oil ring is not doing its job.

Worn compression tells you mainly about the top 2 rings. They can be good and the oil ring may not be good.

 

[Donald]

As other have said, the engine is tired. If you have the time and skill and tools, RockAuto has a re-ring kit for $162 that includes rings, connecting rod bearings and gaskets.

Spending much more than that does not make sense.

If you cannot do the work yourself, then drive it until it dies.

 

[andrewjoelpeters]

Originally Posted By: Donald
As other have said, the engine is tired. If you have the time and skill and tools, RockAuto has a re-ring kit for $162 that includes rings, connecting rod bearings and gaskets.

Spending much more than that does not make sense.

If you cannot do the work yourself, then drive it until it dies.


Okay, thanks for the guidance. I'm going to pull the valve cover this weekend to check the valve stem seals, but that's starting to seem a bit unlikely to me. I'll also plan on doing a leakdown test.

If it is the rings, I'll at least tackle it for the experience under the hood, but I'm not sure when I'll be able to free up the necessary time. Will I do much damage if I keep driving it this way for a couple more months?

 

[Quest]

valve stems are well-hidden behind the valve springs, rocker arms, etc.

In other words: you simply cannot "view" or "inspect" them w/o taking the upper valvetrain apart.

As for the rings, do a wet/dry compression test to confirm the status of your engine, and then simply drive it for the next little while before you can come up with the money to overhaul it.

No use dwelling on a subject that is heavy on the technical info ...esp. on an old, tired, worn engine.

Take care,

Q.

 

[TFB1]

Yep you'll have to know what you're looking at to have any idea if the seal is bad, basically it's usually possible to see the seal under the spring but that's about it...

If you can see the seals, prodding with a small screwdriver or pick will give some idea of condition... If the rubber is supple then they are probably OK, but if it's as hard as the cast iron head(yeah slight exaggeration), there's a good chance new seals will help with the smoking...

 

[andrewjoelpeters]

Originally Posted By: TFB1
If you can see the seals, prodding with a small screwdriver or pick will give some idea of condition... If the rubber is supple then they are probably OK, but if it's as hard as the cast iron head(yeah slight exaggeration), there's a good chance new seals will help with the smoking...


Awesome, thanks. I've been studying up on this guy: http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2327558

 

[Quest]

Those are good quality info from BITOG member's postings.

Learn as much as you can and enjoy.

Q.

 

[andrewjoelpeters]

Okay,
I did a compression test yesterday, and had, in order: 105 psi, 120, 100, and 100. Put a teaspoon of oil or so in the first cylinder and compression jumped to 120 psi. On all cylinders the compression built slowly with each crank -- usually going up by 30 psi or so per crank. The only exception to this was the second cylinder, which jumped to 60 psi on the first crank and went to 120 on the second. The first cylinder did the same after I added the oil. So, rings it is?

Also, my new (500 miles) spark plugs were already showing some ash deposits, except the spark plug in cylinder 2, which was very oily.

That's what most of plugs looked like.

And that's the plug from cylinder 2.

 

[andyd]

If you pay attention to the oil consumption and keep it topped off. If you drive it easy. Eventually a bearing will spin or the engine just won't start. Looks to be a dead plug in #2, maybe just a bad wire or cap. Try a 20w 50 dino oil.

 

[jrustles]

Rings for sure. Not only will oil slip past them, but the blow by pressurizing the crankcase can be driving oil into the intake stream. A rebuild is imminent

 

[TFB1]

With 120 psi in #2 and a oily plug, it's badly carboned in that cylinder... Sooo either the valve stem seal is non existent or oil is getting by the rings on that cylinder...

If it were oil in the intake due to blowby, all cylinders would be affected not just #2...

 

[andrewjoelpeters]

Originally Posted By: TFB1
With 120 psi in #2 and a oily plug, it's badly carboned in that cylinder... Sooo either the valve stem seal is non existent or oil is getting by the rings on that cylinder...

If it were oil in the intake due to blowby, all cylinders would be affected not just #2...


Interesting. I don't see any smoke on startup, but I also remember you saying that there isn't necessarily smoke on a cold start even with bad valve stem seals. Any other diagnostic that might help me figure out which one it is?

 

[berniedd]

At the very least, you need a ring job and valve stem seal replacement. The only sure test for bad valve seals is to change them. Visual inspection just won't do. I had bad valve seals in my engine and it had oil consumption issues. A quart every 800 miles. There was no start up smoke, but it did smoke some when I revved it above 1600 RPM. Piston rings and PCV were OK. Oh yeah, when you tear down the engine, pay attention to the piston to cylinder clearances also.