rebuild engine

[bushbean]

My 3G has over 1/4 million miles. The oil turns black 100 miles after an oil change. I think the engine is worn out. Should I pull the engine out and rebuild it? Or find a used low mileage engine?

[gfrg88]

Up to you.. depends if you're willing to drop some cash or not.. Cheapest, quickest, and easiest way would be getting a lower mileage engine.. do a compression check on your current engine.. Sounds fine to me.. the oil is supposed to get dirty..

[Dr_Snooz]

There's a risk to buying an unknown engine. The downside if you get a bad one is pretty steep too. I will only rebuild engines myself now.

[MessyHonda]

check for compression. also how does the engine feel? slugish or still has some power for the weight of the car.

[rocketman]

My '89 3g has over 1/2 a million miles . . . oil turns black 100 miles after an oil change . . . and always did. I've changed it every 3000 miles more than 160 times, does it every time. Our "95 Civic gets it's oil and filter changed same way . . . same oil . . . in fact same filter . . . the oil gets gradually darker after the oil change . . . from honey to brown to dark brown to black by the 3000th mile. What's the difference? The '89 is carb'd and the '95 is injected, someone told me that's why it turns black sooner. I don't know. Never has made a difference to either car. Rocketman

[bushbean]

check for compression. also how does the engine feel? slugish or still has some power for the weight of the car.

Car drives pretty good. But engine sounds noisy when idling, like valve noise or pulley squeel.

Engine oil turn black after just 100 miles of oil change. It does not seem to burn oil.

PCV valve is good, not plugged up.

Spark plugs are a little bit whitish.

I just did a compression test.
Cyl 1: 197 psi
Cyl 2: 190
Cyl 3: 200
Cyl 4: 195

I forgot to prop open the throttle. Does it matter? So how are those numbers?

Any idea why engine oil turns black so quickly?

[Vanilla Sky]

Blowby will cause the oil to turn black quickly.

Refresh my memory. How long have you owned the car? Is it possible that it was poorly maintained by a previous owner, and the black oil is bits of gunk in suspension? I think it might me a case in which sending a sample to Blackstone will tell more about the motor than any other test. If you send off, you'll be able to find out what's making its way into your oil.

In my experience, I've always had pretty dark oil coming out of my 3geez. This motor doesn't seem too easy on oil.

[Dr_Snooz]

Those numbers are great! Better than a new engine. Unless you have forced induction, they aren't right.

Oil usually turns black because of blowby past the piston rings. That usually results in low compression numbers. In this case, something else happened.

Can you take a vid of the noise?

[bushbean]

Those numbers are great! Better than a new engine. Unless you have forced induction, they aren't right.


Really!? Oh my gosh. The engine is 240,000 miles old, all stock. And it's never been rebuilt. I know the previous owner. He owned the car since 1988, and he babies it from day one. I've had it for a few years. Since I bought it, it's been turning oil black. I don't drive it much, probably put less than 10,000 miles on it.

[MessyHonda]

yeah engine sounds good maybe you just need a valve adjustment

[bushbean]

I replaced the P/S pump and adjusted the valves. The engine got quieter. It's pretty quiet on the road. But when idling, I can still hear some noise, sounds like the pulley bearing.

So, when I do compression check, I just let the starter crank the engine until the gauge stops going higher. Is this the right way to do a compression check?

Is it possible that the high compression number is result of carbon?

I really don't like the black oil. Is it ok to replace just the piston rings? Ane while I'm at it, I can clean off the carbons.

[YK86]

Those numbers do seem high. The proper step is to have the engine at normal operating temp, test one cylinder at a time (only remove the spark plug from the cylinder you are testing), have the throttle wide open, and crank til the gauge stops rising.

As for the carbon, it is a possibility if those numbers really are right. Seafoam for a one time thing, or just using good gas with a cleaning additive for a length of time like Techron should help a bit to clean it out.

If you don't have much cash right now, I would just leave the motor (no rebuild) if it's not knocking/making seriously bad noises or lacks power. Are you losing any oil between oil changes?

[cygnus x-1]

Modern motor oils have detergents in them which keep contaminants in suspension instead of letting them build up inside the engine. This is a good thing because it allows the filter to do it's job. Particles that are smaller than the filter mesh size will stay in suspension, making the oil darker. After so many years the engine builds up carbon deposits that get into the oil and turn it black. As long as you keep changing the oil at the recommended intervals it's nothing to worry about; especially since your compression numbers check out ok. Which BTW, I wouldn't get hung up over them being a little higher than the factory spec. The highest one is only 12% off the nominal, which is really not that far off. For one thing it's a *nominal* value not a maximum so there will be some natural variation. You compression tester gauge could read a little on the high side. There are likely also carbon deposits built up in the chambers that are raising the compression a bit. Carbon deposits around the piston rings will also reduce natural ring gap blow-by.

If you're paranoid you could do a Seafoam treatment to clean out some of the deposits. You could also drop the oil pan and clean it out. And then of course there is always the "Italian tuneup".


Regarding the noise, some valve clatter is normal on these engines because of the solid rocker design. If there is a dry bearing kind of sound it might be the timing belt tensioner, water pump, alternator, AC compressor, or PS pump. A simple diagnostic method would be to remove each accessory belt and see if the noise goes away.


Overall I think your engine is fine. Compression is good, no excessive oil consumption, power is fine, I assume fuel mileage is still ok? Don't look for problems that aren't really there.


C|

[bushbean]

Yes, mileage is great, over 30 mpg. And the engine doesn't burn oil.

I didn't know the oil pan is supposed to be cleaned. I just spent all day replacing the oil pan gasket. I didn't clean the oil pan. It didn't seem all that dirty to me though.

I guess I'll do the Weber carb upgrade next.

[Vanilla Sky]

If you had the pan off and it seemed clean, then there's probably no use cleaning it. There's always going to be some gunk in your motor. Keeping the oil changed is what gets rid of that gunk.

What kind of oil filter do you usually run? There's the possibility that it's bypassing oil instead of filtering it.

[lostforawhile]

Really!? Oh my gosh. The engine is 240,000 miles old, all stock. And it's never been rebuilt. I know the previous owner. He owned the car since 1988, and he babies it from day one. I've had it for a few years. Since I bought it, it's been turning oil black. I don't drive it much, probably put less than 10,000 miles on it.

this is why your oil turns black so fast, the car needs to be driven, the oil needs to heat up to get rid of the crud in it that needs to boil off, change the oil, get a good filter like a WIX, pack a lunch and spend a day driving it. make a point of doing this