Replacing seals in 425
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500, 472, 425, 368 Discussion, Replacing seals in 425 in Cadillac Engine Technical Discussion; How difficult is it to replace the seals, pan gasket etc on a late '70s 425? I'm thinking about buying ...
  1. #1
    Highway Star is offline Cadillac Owners Fanatic
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    Replacing seals in 425

    How difficult is it to replace the seals, pan gasket etc on a late '70s 425? I'm thinking about buying a '77 CDV, and the guy told me it was leaking a little oil. Haven't seen the car yet and was wondering what kind of a headache would be involved with fixing the oil leak. The car supposedly has around 66K miles. I don't know if it's the rear seal or not, but he said the oil was around the front trans area. Thanks.

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    The Ape Man's Avatar
    The Ape Man is offline Cadillac Owners Connoisseur
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    Re: Replacing seals in 425

    You might get lucky and find a leaky oil pressure switch or a botched intake manifold repair job. Both would allow oil to run right down the rear of the engine. These engines usually don't develop leaks from the pan or rear main seal.
    All bets are off if some hack has worked on the thing.
    The pan gasket CAN be done with the engine jacked up. Rear main seal can be done in the car but it is just better to pull the engine at that point.

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    Highway Star is offline Cadillac Owners Fanatic
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    Re: Replacing seals in 425

    Well, that sounds encouraging. The car is a few hundred miles away, so I'm going to plan a trip soon to go take a look at it. Thanks for the info.

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    caddydaddy is offline Cadillac Owners Connoisseur
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    Re: Replacing seals in 425

    I've changed the rear main seal with the engine in the car. It's not that hard of a job to do once you get the oil pan off and out of the way!
    But Ape Man is right, check for oil pressure sender leaks and the intake gaskets. The sender on my 472 is leaking right now!

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    The Ape Man's Avatar
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    Re: Replacing seals in 425

    The thing is, if you need a rear main seal then the main bearings are probably shotski. The neat thing about these engines is that they are large enough to easily remove the crankshaft without pulling the heads off and pistons out.

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    caddydaddy's Avatar
    caddydaddy is offline Cadillac Owners Connoisseur
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    Re: Replacing seals in 425

    Quote Originally Posted by The Ape Man
    The thing is, if you need a rear main seal then the main bearings are probably shotski. The neat thing about these engines is that they are large enough to easily remove the crankshaft without pulling the heads off and pistons out.
    True, but in my case, the rear main seal was leaking less than 1,000 miles after the engine was rebuilt! Damn cheap seals!

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