Oil burning Honda w/ 248k miles

[rollingrex33]

I've got a 1.6L honda motor in my 1991 CRX that has become a severe oil consumer. When I first noticed the oil consumption, at around 235k, it only would smoke out of the tailpipe whenever I was above 5500 rpms and under load. Now, with around 248k miles, it smokes out the tailpipe at anything above 2500 rpm and even with the slightest load. A good time for ARX I thought.

I'm about 600 miles into the first cleaning phase and it appears that the oil burning is a bit worse during the cleaning phase. Is this to be expected?
After 600 miles of the initial cleaning phase, I've driven conservatively and used about a quart of oil, should I be adding 2 oz. of ARX for each qt of oil that I replace?

I have a feeling that this motor is suffering from either worn valve seals/guides or worn out oil rings on the pistons. I've checked static compression on the bottom end and it is very good with very minimal deviation from cylinder to cylinder (220 psi +/- 5 psi). I've also had a leakdown test done on the motor recently and it passed with flying colors. I would imagine that if air from a leakdown test would not make it's way past the piston rings, then oil would NOT be able to get by the rings during engine operation.
I've seen oil piston rings on these little motors and they look pretty robust, I have a hard time imagining that these would EVER go bad. My question is this; how do I pinpoint where my motor is using oil from, the head or the bottom. It would be extremely easy for me to pull the head and rebuild it, but that would also be an opportune time to remove pistons and replace the ring packs. The later would be more time consuming and would cost more money in addition to the head work. What symptoms do I look for to determine where my motor is using oil from?

Sorry for the length, I just need a good educated answer.

 

[RF Overlord]

quote:

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What symptoms do I look for to determine where my motor is using oil from?

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rex:

I was taught that if the motor smokes under load, then it's the rings...if it smokes when you accelerate after the motor has been idling, or after coasting, then it's the valve seals/guides.

In other words, if it smokes with low intake manifold vacuum, then it's rings; if it smokes just after having high vacuum (like idling or decelerating), then it's the valve seals.

Also, I would imagine that it's possible your oil control rings be worn, but the compression rings be OK...the oil rings are designed to scrape excess oil from the cylinder walls during the downward stroke, while the compression rings are designed to be loaded by gas pressure from above, so it's certainly conceivable that your leakdown test would be fine, but still be burning oil.

[ April 01, 2004, 06:18 PM: Message edited by: RF Overlord ]

 

[rollingrex33]

So would it be feasible to replace the rings without honing the cylinder walls (without pulling the motor)? Or is that just asking for trouble? It smokes so often, it is hard to tell if it smokes more under load or if it is just always smoking. It started out by only smoking at high rpms, does this indicate seals or rings?

 

[RF Overlord]

Replacing rings without honing is asking for trouble, especially on a motor with that many miles...if you have the pistons out anyway, honing isn't THAT much more work, and at least then you know the new rings will seat properly.

And since you'll also have the head off, just put new valve seals in, too...they're (relatively) cheap...and MUCH easier to do with the head off.

 

[Jeff in Western WA]

Geez 235 K, just some good 'ol SAE 30 in the winter, SAE 40 in the summer w/ a filter change each time, worked well on my well worn 231 (3.8L) Sunbird years ago, my pressure would drop to 2 PSI when "hot" in gear, nice red light on dash..

...hey, throw some "motor honey" in it too....I'd not bother opening that motor unless you rebuild it all including the head...I'd just keep driving it if it runs well, are the plugs clean?

 

[DZello]

i replaced my rings on my 92 civic (d15b7) without honing the cylinder walls and everything is perfect after 40 000 km.

 

[AV8R]

The compression and leakdown tests won't tell you anything about the condition of the oil control rings. The Honda motors seem to have a problem with the oil rings losing tension after a lot of miles, rather than wearing out. If you don't make any big blue puffs on startup in the mornings, your guides and stem seals are probably ok. Do a decent engine-out honing and ring replacement. If the guides are showing wear (have them miked) install a set of manganese bronze guide liners and be done with it...they'll last you forever. (this is a job for a competent head shop with a Serdi, not a mechanic)