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Thread: Oil Leak - Ideas?

  1. #1
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    Default Oil Leak - Ideas?

    Have an 84 bird, 3.8L, 73K miles. Has developed a significant oil leak. Trouble is eveything is so wet, its hard to tell what is causing mostly. I have done the valve covers, 3x since over 15k miles, both with the rubber gasket, then back to felpro cork. Its not the valve covers. The bell housing, the oil pain, the front cover, all is soaked, but the drips come off the right side of block area, after running down around the starter mounting area and off the edge of cover that seals off the converter area (by the starter). Crossover is getting some drips on it and smoking a bit (hard to tell from all the caked on cooked oil on it). The right side of the block is dirty, but I dont see any significant leak from there in the region that I can see. Itll drip maybe 4-5 drips per minute just idling, more if revved.

    Any ideas? Im getting close to saying bye to this car, but this is a spare mess around car, but this oil dripping is just too messy to continue.

    Thanks for the tips.

    Russ

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    The only way you can be sure is to clean it up. I would spend a couple bucks on some degreaser (or even brake cleaner) and clean up the suspected area. Then start it up and see if you can see where it's coming from.
    CoogarXR

    1986 LTD Wagon
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    I wouldn't be surprised if you found the intake leaking at the rear end seal. I've see some older 3.8L cars (of all types) leaking from the rear of the intake, in a couple of cases I attributed it to increased backpressure caused by cats becoming obstructed. Be ready for this rabbit hole to go deep.
    1988 Thunderbird 5.0
    GT40P, TFS-1, KB domes, 30#, MAF conversion, Explorer GT40 Upper/Lower, Smog delete, Wide Ratio AOD Mod, Unlocked Speedo, 3G Charging System Upgrade, Hi-Torque Mini Starter, 3.73 LSD, BBK 1 5/8 unequal headers, H-Pipe.

    88 Thunderbird/Cougar EVTM
    (Thanks to Trinom for hosting)

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    Quote Originally Posted by TheFoeYouKnow View Post
    I wouldn't be surprised if you found the intake leaking at the rear end seal. I've see some older 3.8L cars (of all types) leaking from the rear of the intake, in a couple of cases I attributed it to increased backpressure caused by cats becoming obstructed. Be ready for this rabbit hole to go deep.
    Interesting thought on the cats. The rear intake seal is seeping a bit as Ive looked back there but it doesnt appear to be losing much as its not all that wer back there. So is this a pretty well know effect of plugged cats (causing oil leaks all over)??

  5. #5
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    Those older cats are pellet-bed style, they failed all the time. The problem with "plugged cats" as most people think of them, is that people only think about obstructed catalysts in their terminal phase where they don't flow at all. It doesn't happen all at once, and up until they completely block, the pressure has to go somewhere. In a lot of cases, pressure backs up until it becomes excessive blow-by. So then the excess pressure is in the crank case, the PCV can't vent it all into the intake, so it finds its way out and once the seals or gaskets are compromised, oil comes out, too. Not saying this is your problem, but keep it in mind. Even if it is the root cause, you'll still need to find and repair the leak.
    1988 Thunderbird 5.0
    GT40P, TFS-1, KB domes, 30#, MAF conversion, Explorer GT40 Upper/Lower, Smog delete, Wide Ratio AOD Mod, Unlocked Speedo, 3G Charging System Upgrade, Hi-Torque Mini Starter, 3.73 LSD, BBK 1 5/8 unequal headers, H-Pipe.

    88 Thunderbird/Cougar EVTM
    (Thanks to Trinom for hosting)

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    Thanks. One thing I should add, is that I use only mobil 1 synthetic in motors, and Im suspect that I helped leaks along by doing this. Ive had 2 of these motors back in the old days, and both motors wore out at low miles (80K ish). They all were leakers, but none this bad.

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    Quote Originally Posted by TheFoeYouKnow View Post
    Those older cats are pellet-bed style, they failed all the time. The problem with "plugged cats" as most people think of them, is that people only think about obstructed catalysts in their terminal phase where they don't flow at all. It doesn't happen all at once, and up until they completely block, the pressure has to go somewhere. In a lot of cases, pressure backs up until it becomes excessive blow-by. So then the excess pressure is in the crank case, the PCV can't vent it all into the intake, so it finds its way out and once the seals or gaskets are compromised, oil comes out, too. Not saying this is your problem, but keep it in mind. Even if it is the root cause, you'll still need to find and repair the leak.
    And I'll say if blow by was so bad as to push oil out of crankcase, the engine would be sorely lacking in power... Engines will usually fill intake/air cleaner with oil long before they actually leak... I've seen cats plugged so badly that engine would start and die, were not losing oil...

    Most gaskets before mid '90s were junk, leaked at 10 years, at 30+ they are all but useless... The '86 HO 5.0 I originally used in my Bird was streaming oil out back of intake, extremely common in those engines... At less than 120K mi My '93 Lighting was pissing oil between block and oil pan, at 191K my '96 F150 5.0 is yet to drip... I dunno how much of improvement is gasket vs the oil pan rail supports, suspect the supports are a major factor...

    Mobil 1 has seal conditioners I doubt it actually caused the leak...

    If it's main bearing seals leaking a high mileage oil may help, but I've never seen any improvement on front cover, oil pan etc gaskets...






    My other rides (that actually do run & drive)

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    1972 Comet GT - 306 C4

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    good point.

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    Is it easier to pull engine or engine and trans together??

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    That depends on you, your equipment, and if you can get a helper. Personally, I've never taken an engine and trans together unless I needed them both out, and even then, I've preferred a drop to a pull. That's only because I have facilities and equipment to do a drop. I've got pics of a Fox drop on here somewhere.

    Speaking of engine pulls, here's what I'm doing today
    IMG_20180111_090720.jpg
    Last edited by TheFoeYouKnow; 01-11-2018 at 08:10 AM.
    1988 Thunderbird 5.0
    GT40P, TFS-1, KB domes, 30#, MAF conversion, Explorer GT40 Upper/Lower, Smog delete, Wide Ratio AOD Mod, Unlocked Speedo, 3G Charging System Upgrade, Hi-Torque Mini Starter, 3.73 LSD, BBK 1 5/8 unequal headers, H-Pipe.

    88 Thunderbird/Cougar EVTM
    (Thanks to Trinom for hosting)

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