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Thread: Pull Engine and tear down?

  1. #1
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    Pull Engine and tear down?

    Hello everyone,

    I'm hoping to get some opinions on how far people go these days with 38 year old engines in an unknown (non-running) state. Is it typical to pull the engine, clean/inspect everything, and replace all of the gaskets/seals/etc? or just address regular maintenance items, known problems, and hope for the best?

    The history that might be relevant:

    - Was rebuilt about 20 years ago
    - Has a pair of welds in the valley from late 90s
    - Successful compression test a few years ago but never got things running at that time
    - Oil leak possibly at the pan but could have been the oil sender.
    - The engine was fine when it was parked - k-jet problem
    - The engine is already torn down to the valley. Removed fuel components, intake, pipes, etc.

    Thanks

    Bill
    Last edited by Bill6298; 12-08-2019 at 07:00 PM.
    Bill

    VIN 6298 - '81 Gray Auto

  2. #2
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    I would start by checking the oil and then doing a compression test with a mechanical oil pressure gauge attached to see what is going on inside. If you have some oil pressure and the compression seems good I would reassemble the motor and try to get it to run. Verify valve and ignition timing as you put it back together. Take the belt off the water pump, you don't need coolant to just see if the motor will start up. Once you can get it to start then you can fix up everything else. I would not just pull the motor and disassemble it without doing some testing. The PRV is a pretty durable little motor and can run for 100,000 miles easily unless you overheat it or run it without oil. My vote is to not take it out unless you have a good reason to. If the clutch is bad you can pull the transaxle, it is easier than pulling the motor.
    David Teitelbaum

  3. #3
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    Quote Originally Posted by David T View Post
    I would not just pull the motor and disassemble it without doing some testing.
    Thanks David. Always appreciated your advice over the years. Doing another compression test makes a lot of sense especially since I have prior results to compare them with.
    Bill

    VIN 6298 - '81 Gray Auto

  4. #4
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    What is: "a compression test with a mechanical oil pressure gauge attached?"

    Is that a type of test gear that does both, or does it mean to attach a pressure gauge on the engine while also doing a compression test?
    Livin' the dream....

  5. #5
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    Quote Originally Posted by Rich_NYS View Post
    What is: "a compression test with a mechanical oil pressure gauge attached?"

    Is that a type of test gear that does both, or does it mean to attach a pressure gauge on the engine while also doing a compression test?
    I was assuming he was suggesting putting an oil pressure gauge where the oil pressure sender is attached.
    Bill

    VIN 6298 - '81 Gray Auto

  6. #6
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    Quote Originally Posted by Bill6298 View Post
    I was assuming he was suggesting putting an oil pressure gauge where the oil pressure sender is attached.
    Thanks. I'm planning to do the same, so I'm interested to understand the procedure. Please post progress updates if you don't mind.
    Livin' the dream....

  7. #7
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    LoL @ earlier


    Depending on which oil sender may be leaking, maybe put the oil pressure gauge in the idiot light port instead and confirm the dash gauge in the process. Kill 4 birds...

    $.02
    If it has sat a long time undisturbed and the valley looks like it is sound. I'd say: Remove and inspect the spark plugs, feel how the crank turns with a breaker bar and socket. If ok, maybe clean around oil leak suspect(s), and without putting anything into the cylinders, record the two tests David mentioned. If not, put an equal shot of thin oil in each cylinder and let soak.
    If it passes both tests (as expected;-), I'd order the gaskets,
    reinstall the plugs and start cleaning EVERYTHING - Here's a good time to consider EFI or that four letter word, depending.

    If it fails the compression test, a Leak Down Tester might be in order. (They have two gauges;-)
    No mention of coolant leaks is a good thing. It would have been better if you had
    pressured up the coolant system earlier...

    If you see any signs of exhaust leaks at the heads, removing the manifolds and inspecting the ports might expose important clues (burnt oil residue, steam cleaned by coolant, etc.) .



  8. #8
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    How are the tests performed on an engine in this state.....just using the crank from the starter?
    Livin' the dream....

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    Here are the steps laid out;
    Verify motor oil in the crankcase, level and quality. If it is really bad or not enough dump it and fill with fresh.
    Remove the oil pressure sender unit by the oil filter and install a mechanical gauge.
    Block the throttle wide open and disconnect the ignition coil (one of the little wires, not the big fat one).
    Remove the spark plugs and using the starter crank the motor for at least 10 seconds. You should see at least 10 psi oil pressure. You can crank the motor by using the key or a starter button directly to the starter.
    Using a compression gauge measure the pressure of each cylinder and write it down. You should "bump" each cylinder 4-5 times (do it the same for each).
    Squirt some oil into each cylinder and check then again (write it down)
    Now the hard part, you must interpret the results. Just post it, that way you can get several opinions.
    Clean and regap the plugs or stick new ones in, hook up the coil, unblock the throttle. Once you get the motor to run and get it to operating temperature change the oil and filter. This is my method of evaluating a motor that hasn't run in many years. If the results warrant it, you could do a leak-down test and/or, using a borescope, look inside. If you don't get oil pressure or 1 or more cylinders are very low, time to take the motor apart.
    David Teitelbaum

  10. #10
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    Quote Originally Posted by David T View Post
    Here are the steps laid out;
    Verify motor oil in the crankcase, level and quality. If it is really bad or not enough dump it and fill with fresh.
    Remove the oil pressure sender unit by the oil filter and install a mechanical gauge.
    Block the throttle wide open and disconnect the ignition coil (one of the little wires, not the big fat one).
    Remove the spark plugs and using the starter crank the motor for at least 10 seconds. You should see at least 10 psi oil pressure. You can crank the motor by using the key or a starter button directly to the starter.
    Using a compression gauge measure the pressure of each cylinder and write it down. You should "bump" each cylinder 4-5 times (do it the same for each).
    Squirt some oil into each cylinder and check then again (write it down)
    Now the hard part, you must interpret the results. Just post it, that way you can get several opinions.
    Clean and regap the plugs or stick new ones in, hook up the coil, unblock the throttle. Once you get the motor to run and get it to operating temperature change the oil and filter. This is my method of evaluating a motor that hasn't run in many years. If the results warrant it, you could do a leak-down test and/or, using a borescope, look inside. If you don't get oil pressure or 1 or more cylinders are very low, time to take the motor apart.
    Nice summary, I'm going to do this with 4519 before I get too deep into rebuilding the fuel system.
    Livin' the dream....

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