This one has several good mechanics stumped

1995 Mitsubishi Galant, 2.4L inline 4-banger, 5-speed manual tranny 66,000 miles, one owner, one driver, always garaged Not a commuter car until 2005. Was used mostly as a weekend runabout and a few long-distance road trips here and there. Often sat unused for weeks at a time. (Owner always drove company vehicles during the week . . . and often the weekends, also)

Looks and runs like new still, except it suddenly started losing oil about a month ago. This vehicle was extremely well maintained, well beyond manufacturer recommendations. For just one example, oil changes were always at (not exceeding) 3,000 miles. For the first ~10 years (weekend runabout) conventional oil was used, 5W30 or 10W30. For the last year, it has been a commuter, and oil is still changed every 3,000 miles, but now synthetic blend 5W30 is used. Other maintenance done has all been expected, "scheduled" stuff like tires, a battery, air filters, spark plugs, a couple brake jobs, stuff like that.

EVERY 3,000 miles, the engine would "use" about 1/2 to 3/4 quart of oil between 3,000 mile oil changes. (nothing odd)

Around mid-February, I checked the oil at around 1500 miles past last oil change (synthetic blend 5W30) It was a half quart low. That didn't bother me. The fact that it was PITCH BLACK did. That was unusual for this car. Oil does get darker/discolored, but I've never seen it black before. Didn't think too much about it. Dumped a half-quart of regular 10W30 in (what I had handy). A week later (and another ~300 miles), I checked the oil again and it was A FULL QUART LOW. Since that time, it has lost (for lack of a better word) a full quart of oil every 250 miles.

Obviously there's a problem. Now here is what has the mechanics stumped. Several good mechanics have looked at this car. These are the facts known so far:

1) There are NO oil leaks. I confirmed this myself, but several mechanics have had it up on the lift and can not find even a minor oil leak. I would expect the underside of the car to be covered in oil if oil was leaking at a rate of 1QT/250miles , but there's no oil at all down there, that anyone can find. My garage floor is oil free. My parking spot at work is oil free. 2) There are no problem codes in the computer. 3) Car starts easily and runs well, but sometimes hesitates on acceleration above about 2000RPM or so (that started around the same time that the excessive oil consumption started) 4) Engine easily passed emissions test while losing oil. In fact, the mechanic who tested emissions noticed the engine was again a full quart low, and added oil. 5) Several (dry) compression tests have been run since oil started disappearing. Numbers on all cylinders on all tests range from 190 - 195 (a couple of 200 readings in there somewhere also). According to Mitsubishi, this is good. According to all mechanics I have consulted, this is very good. The last compression test done, I witnessed myself. I read the gauges as (cylinders 1 - 4) 195 - 195 - 190 - 190. A "wet" compression test was also done at one point, and I was told that it was GOOD, but don't remember the readings. Other mechanics have told me that the wet test was redundant anyway. (because the dry test looked good) 6) One mechanic told me that there's no oil inside the tailpipe. I guess that's good? 7) Car has sat for several days (once) after excessive oil consumption started. While sitting (not driven), it apparently lost no oil. 8) In desperation, one mechanic drained out the synthetic blend 5W30, changed the oil filter, then refilled the engine with * 15W40 * conventional oil. According to the Mitsubishi service manual, that is OK for the engine (it'll take from 5W30 up to 20W50?, or somewhere there). But, the thicker oil made no difference. The car still loses a quart of oil every 250 miles, when driven.

To put it bluntly, where the HELL is the oil going? I'm kind of attached to the car, so I'll throw money at it. But first I need to know what the problem IS. I'm stumped. Several good mechanics are stumped. No rings or valve problems, no oil leak, emissions good, exhaust not discolored, but oil is disappearing at rate of 1 Quart every 250 miles. Is this a wierd Mitsubishi quirk that none of my mechanics have heard of? That is, makes oil disappear without burning it or leaking it???

Reply to
George K
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Possibly leaking into the torque convertor or tranny? What was the mechanics' take on the black oil?

acceleration

Reply to
ks

======== ======== When was the last time the spark plugs were changed? Before or after you started to notice the oil consumption?

My suspicion........... the oil is going out through the exhaust. The catalytic convertor has so far been able to contain the oil and burn it off without allowing it to show up at the tail pipe. If the compression tests are showing good, and the techs doing the tests haven't mentioned wet or fouled spark plugs,........I would suspect that the oil is going out through the vacume system, likely a PCV concern.

My suggestion........ check the PCV valve.......see if the hose is oil soaked on the inside. I would also suggest pulling the induct hose off the throttle plate and see if there's any oil up around the throttle plate.

other than that.......I'm admitting I'm stumped too if your techs have checked everything else and it's all coming up good.

hopefully helpfull, let us know.

~:~ MarshMonster ~tech~

Reply to
Marsh Monster

ks wrote: Possibly leaking into the torque convertor or tranny? What was the mechanics' take on the black oil?

===== ===== KS, please detail how in the world the oil is going to leak into the tranny?

(we'll let you slide on the torque convertor part......it's a manual ks)

any whoooooo.......

would be interesting to here yer take on how the oil is getting in the tranny.

~:~ MarshMonster ~:~

Reply to
Marsh Monster

Most likely cause of the oil consumption is worn valve seals. You can try this easy test. With the engine fully warmed up let it idle for around 15 -

20 minutes, then bring the rpm's up quickly ( around 3000 rpm ) and look for blue smoke from the exhaust. If blue smoke is present in the exhaust you need to replace the leaking valve seals. This is a common problem on Mitsu's but usually occurs around the 100,000 mile mark. I would suspect the valve seals are dried out from the car sitting for so long.
Reply to
Mike

Or start it cold in the morning and look for same bluish smoke after reving the engine once quickly. Smoke should go away well within a half minute if the culprit is valve seals.

Mike, do you find specifically that the exaust valve seals deteriorate in the area of the rubber coating inside the seal that make them fit snug over the valve guide (i.e. not the seal lip)?

Toyota MDT in MO

Reply to
Comboverfish

No, they are still a tight fit over the guide. The seal lip hardens and loses it's elasticity, sometimes even cracking. From my experience this is almost always caused by lack of oil changes when it occurs at such a low mileage. If the vehicle is well maintained they generally last well over

100,000 miles.
Reply to
Mike

Wild guess: check the radiator for oil.

Reply to
B.B.

One mechanic thought that gasoline was in the oil, but that was just one opinion, and contradicted by other mechanics. I'm not a mechanic. But, if oil was leaking into torque converter or tranny, wouldn't either place be over full by now? At some point, I imagine that the oil would escape the car completely, or the car would stop "losing" oil. I forgot to mention earlier that two new PCV valves have been installed since the engine started losing oil. The PCV valve was probably good to begin with, but it was changed a couple times anyway.

Reply to
George K

I forgot to mention earlier . . . since the oil started disappearing (for lack of a better word), the PCV valve has been checked a few times. It was apparently good, but it was replaced anyway (twice), because the mechanics were desperate to try anything. The spark plugs were changed JUST before the car started losing oil (about a week or two before, roughly). They've been inspected a few times since the oil loss started. The plugs are not wet or fouled. I don't know if the throttle plate has been checked.

Reply to
George K

OK, I will try this test. I've got nothing to lose except a little gasoline, so what the hey. What you say makes perfect sense. The car did sit for long periods. At one point, I believe I didn't even start it for about 3 months. So having the valve seals dry out is (I guess) quite possible.

But . . . I was told if there was a valve problem, that the engine would fail a compression check. Is it possible to have leaking valve seals AND good compression? I honestly don't know, which is why I'm asking. Last dry compression test was 195 195 190 190, and that is about what all of them have been, since oil started disappearing.

Reply to
George K

Shit. I think that's the one thing that hasn't been checked yet. I will check it myself. I'll be shocked if I find oil in there, but the oil is going somewhere, so why not check the radiator? :)

Reply to
George K

If the oil leak is down the valve stems, then, no, it would not show up on a compression test. And as another poster has mentioned, your catalytic converter could be active enough that it is 'burning' the oil so completely that oil would not show up in the tailpipe (yet).

If you have someone watch the tailpipe when you first start it up in the morning, and they see blue smoke, then that is a good indication of valve stem leakage. Reason: Oil drips down the stem after you shut it off, and only partially ignites when you start it the next morning. The converter is cold so does not oxidize this first shot of oil.

The radiator check is good too. If you are losing oil into the radiator, it will (at the rates you mention) belch over in the the coolant reservoir. Then it will eventually start blowing out of the coolant reservoir.

Reply to
<HLS

Ah, but there's your misunderstanding. Valve problems will indeed fail (or at least show up on) a compression check, but only if the problem involves whether they close properly or not. Valve guide seals being toast won't, unless the seals are so far gone *AND* the valve guide/valve stem is so worn that the valve stem is slopping around enough to "c*ck" a valve and prevent it from seating. (in which case, you've almost certainly got a hosed valve guide, valve stem, or both, and possibly a dead valve seat besides, along with the seal being bad - Nothing you've said yet gives any indication of that being the case, though.)

Yes. Completely possibly. In fact, so possible, I'd call it unusual for a car with "just" bad valve guide seals to show any hint of problem in a compression test.

The "idle for a while then rev" test should show you one way or the other, but based on what's been covered so far, I'm betting on the seals. You've already eliminated leaks, compression testing says rings are good, no oil in the radiator, but oil is still "going away" - These pieces all combine to make a picture that says "Then it's leaving through the tailpipe as smoke". The only path from crankcase to tailpipe that hasn't been eliminated is the valve stems/guides/seals.

Reply to
Don Bruder

Yes, it is possible to have good compression and leaking valve seals. The valves seals jsut keep engine oil from leaking into the cylinders when the engine is running.

Reply to
Mike

Hmmmm . . . I'm starting to suspect the valve guide seals.

Reply to
George K

This is some good information. I haven't checked the radiator yet, but I'd be surprised if the oil is in there. I'm starting to suspect valve guide seals. Will idle for a while then rev. Thanks everyone

Reply to
George K

TOP POST

The head gasket (from oil line to exhause) could have a split. Valve seals seem more lilkely though.

George K wrote:

Reply to
Alan

Turbo model, isn't it? (normal cranking compression in the 90's gives it away)

I'll bet the turbo is dying.

Black oil early is a sign of combustion products contaminating oil. If rings are ruled out, nthing else fits. Worn valve guides, PCV valve, etc, ar unlikely to cause enough blowby to blacken the oil so soon, and you're not running rich, or economy would suffer.

My bet is the turbo is going south.

Reply to
~^Johnny^~

Nope, not a turbo. Pretty sweet ride (IMHO), but not turbo-charged.

Reply to
George K

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