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Engine's burning oil - how much longer will it last?



  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 58,459
    Not buying it either. You can't fix worn rings with something in a can. We are talking here about missing metal that's worn away, in a combustion chamber exposed to incredible heat and stress. So a can of goo is going to fix this?

    There MIGHT be situations where oil-burning is correctable, but actually engine wear is not one of those situations.

    Also, using engine sealer is a bad idea. This swells the seals temporarily but they become flabby and rubbery and will leak worse shortly.

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  • canoeboatercanoeboater Posts: 1
    edited August 2010
    I have a 1997 Subaru Outback with a manual transmission. 97,000 miles. For the last five years or so, the car has been driven occasionally, but not for many miles , because I have a company car. Despite this, the car still runs very well.

    Now the car has oil leaks from the engine block and oil pan, and a transmission leak from the front end. The estimates for repair are a few thousand dollars, which I have trouble justifying on a car this old. I am trying to decide whether or not to keep driving it and feeding it oil until it dies, or replace it.

    I have been monitoring the levels of both the engine oil and the transmission gear oil. Both leaks appear to be slow leaks. I have seen very little fluid in the driveway, and no tailpipe smoke. I see some smoke from the engine compartment when I sit at stoplights for long periods, presumably from engine or transmission oil dripping onto the exhaust pipe. There is some odor.

    The car runs well, and I don't mind feeding it oil for a while. However, I do not want to get stuck somewhere. I often carry canoes/kayaks on the roof rack, and having a breakdown with boats on the car could be a bit complicated.

    My question is this: Do these kinds of leaks typically lead to a sudden catastrophic failure that would leave me stranded someplace? Or, will the car just gradually burn more and more oil and lose more gear oil?

    Also, do the engine oil stop leak products that are widely available on the market actually work, without harming the engine? Is this a viable strategy for engine oil leaks?

    Thanks in advance for your help.
  • kiawahkiawah Posts: 3,666
    The vehicle is probably worth around 2-3K if trying to trade in or sell.

    Since you already have a reliable daily driver company car, I think the decision on this is partially dependent on how much the value will reduce if you keep it a year, and the oil leaks get progressively worse. Just keep the thing alive to haul your sport gear, and don't spend a ton of money on it.

    If this were mine, I'd probably look to replace the top valve cover gasket, it that is where it is leaking and dripping down on the exhaust pipes. That should be much easier and cheaper to repair. I'd then degrease and clean off the engine and transmission, which would give you the ability to monitor closer where and how much it's leaking.
  • shiposhipo Posts: 9,152
    First off, unless you run the engine (or transmission) low on oil, then they'll go on running for a long-long time.

    Second, for the cost of the gasket replacement service you can buy lots and lots of oil and still never justify the cost of the service, even if you drive the car a half of a million miles or more.

    Third, as a general rule, engine stop leak products do not work well.

    Finally, long ago when I was quite poor and needed a car desperately, I bought a car that was leaking a fair amount of oil, burning a fair amount more (to the tune of 100 miles per quart), and the previous owner's mechanic told him that the engine wouldn't go more than a few hundred miles more before suffering a catastrophic failure. I was pretty handy with engines and figured I'd take a chance on it; I paid $250 for the car which had 105,000 miles on it at the time. At the 220,000 mile mark the oil consumption hadn't gotten any worse (better actually as I'd replaced a number of leaky gaskets), and the engine still ran well. By then I was making a little more money so I yanked the motor and rebuilt it. My bet is that that darn thing would have gone easily twice that mileage without being rebuilt, but I finally just got tired of putting oil in all of the time. :)

    Long story short, I say keep your car, feed it oil, and save your money. :)

    Best regards,
  • srs_49srs_49 Posts: 1,394
    edited August 2010
    I agree with Kiawah and Shipo. Oil is cheap, relative to replacing crankshaft and driveshaft seals. Valve cover gaskets can probably be done for less than $50, if you can do the work yourself. Forget about the engine stop leak products.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 58,459
    Before you do anything, you should have the car checked for the dreaded Subaru 2.5L engine's headgasket leak---which occurs right about at your mileage, and which can cause external as well as internal leakage.

    If you're lucky, maybe the oil leaks are not so hard to fix...if it's just valve gaskets, the only real risks are a) running out of oil and b) excessive oil catching fire at some point--if it started leaking A LOT.

    A good Subaru specialist should be able to diagnose for head gasket failure pretty easily and cheaply.

    If you need head gaskets, that's also a good time to fix the transmission leak. If it's a very clean car, otherwise functioning well with good AC, upholstery, tires, brakes, etc., I'd say go for it. These cars can run a long time. But if the leaks are only one of a number of other issues, and if the car is kinda beat, I'd let it go.

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  • hpmctorquehpmctorque Posts: 4,600
    Interesting, shipo. Can you tell us what kind of car it was?
  • shiposhipo Posts: 9,152
    edited September 2010
    A 1966 Plymouth Valiant 200 with the "Certified Bullet-Proof" 225 Slant-Six engine. :)
  • hpmctorquehpmctorque Posts: 4,600
    Oh, well, that explains everything. My parents owned a couple of those, and other family members owned a couple more. I can't think of any engine that was more durable and rugged in its day. I'll vet the Mopar slant-six would give a Mercedes diesel of the '60s and '70s a run for its money.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 58,459
    They have a lot in common actually. Both long-lived, noisy, like to burn oil, agricultural in personality, and they go shakey-shakey if neglected.

    The Slant 6 was simpler of course. That thing has about 4 moving parts. I've seen wood stoves more complicated than a Slant 6 engine.

    I've seen Slant 6s wheeze and cough and throw out a smoke screen and wobble and sputter and refuse to start, but I never actually saw one that had thrown a rod.

    Benz diesels liked to crack cylinder heads. You'll often find that the claim of "this engine has XXXXXXXXX miles on it" doesn't include the cylinder head.

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  • I had a "Slant-6" in a 74 Plymouth Valiant. The engine developed an oil leak and needed a quart every 500-800 miles. Being the kid that I was, (18 and should have know better), tried drag racing a friend and didn't check the oil. :blush: Needless to say, it threw a rod, (Rod Knocking) Check the oil and there was no oil on the stick. Took three quarts to bring it back to full. But would you believe, I drove that thing another six months with it knocking before it finally quit. Put another one in it from the junk yard for $150 and drove it another year. :shades:
  • new head,oil,and cover pan gasket new oil pump and new connecting rod bearing and new lifter and its still has a light tap to it i know what else to do help.....
  • shiposhipo Posts: 9,152
    edited September 2010
    "Needless to say, it threw a rod, (Rod Knocking)..."

    You got it right the second time. :)

    Typically a "thrown rod" implies that a rod has broken somewhere between the crank throw and the wrist pin. In many cases, given that the rest of the engine still has a few revolutions left in it, the remainder of the rod still attached to the crank manages to punch a hole in the side of the block.

    In the case of your 1974, the usual term is "spun a bearing". :)
  • isellhondasisellhondas Issaquah WashingtonPosts: 19,809
    I saw a guy throw a rod on an old Chevy one time. It somehow missed hitting a water jacket and the guy drove it home about 20 miles afterwards.

    Can't imagine the noise it must have made!
  • shiposhipo Posts: 9,152
    Yeah I've seen holed skirts as well (the engine block kind that is); not usually too many water passages in the skirt. :)
  • bottgersbottgers Posts: 2,030
    Since I haven't been in here for a while I'd thought I'd post an update. My consumption issue has slowly gotten worse. It now uses a qt about every 800-1000 miles. However, I did replace the spark plugs and wires a couple of months ago and none of the plugs looked to be oil fouled. In fact, they all appeard to have the nice hazy look you typically see with a properly running engine. The engine also doesn't smoke (at least not that I can see anyway), it still runs fine, doesn't seem to have lost any power, and it still seems to do just as good fuel economy wise as it ever did. So I just keep a few extra qts of oil in the trunk and keep driving it...why not?
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 58,459
    Indeed, why not? You might try an experiment, which requires a friend to follow you in their car.

    Accelerate on some empty road, maybe say in a lower gear so that the engine revs up pretty high---then let your foot OFF the gas until the car slows way down, and then PUNCH it.

    Then ask your friend if he saw a momentary puff of blue smoke as you punched it.

    If he did, this would verify worn valve guides or valve stem seals.

    By driving the way you did, you created high engine vacuum when you let off the gas, and then LOW vacuum when you punched it---this would suck any oil from the upper cylinder head past the worn guides or seals and into the combustion chamber.

    If you are just idling, or revving the engine while standing still, you don't create the conditions necessary to suck oil past the worn guides and seals. So you won't see smoke. And seeing it as you drive is difficult, as the smoke would be temporary.

    If you want a definitive answer, get a Cylinder Leakdown Test performed and post the results here.

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