DIY Compression Test on engine out of frame? (5th Gen)

Discussion in 'Mechanics Garage' started by RC46-SP2, Mar 17, 2018.

  1. RC46-SP2

    RC46-SP2 New Member

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    Stupid question, probably, but anyway...

    The story goes thus.

    I've recently taken delivery of a bare 5th Gen engine, supposedly with ~67,000kms (~42,000 miles) on it. The plan is to refurb it with new T/Stat, water pump, under throttle body hoses/o-rings, spark plugs, stator etc. and keep aside as a "spare" for when my higher mileage engine "goes". (The current engine has ~136,000kms (85,000 miles) on it).

    Anyway, before I get too carried away, I'd like to at least get a compression test done on it, to give myself a level of comfort that the bottom end is OK. Granted, a leak down test might be a better indicator. But I'm told that it requires a "warm" engine, and my spare isn't likely to be being started any time soon...

    I'd discussed taking the engine to a local bike place and getting them to compression test, but - to be honest - am a little apprehensive about trying to man handle the engine into the back of our car. I can lift the engine off the trolley it's on (tried about half an hour ago). Just not sure I won't drop it, or damage our car trying to get it into the back of it...

    So, how easy is it to grab a basic compression tester, and do the test myself here? What's involved? (I can do the basics of servicing and disassembly/re-assembly, but am a bit of mechanical numpty other than that ;)

    Thanks in advance.
     
    Last edited: Mar 17, 2018
  2. Darth Vader

    Darth Vader New Member

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    Dont really know if im honest but as long as you can get it to spin on the starter you should be able to get some readings id of thought.
     
  3. DaHose

    DaHose New Member

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    You should have zero problem testing. Just make sure you have good oil level, mount the engine itself level, and put 12V to the starter. You just need to be sure you have the right kind of adapter for the spark plug thread.

    Just for giggles I'll share that I have a 1987 M6 with a very tight, and deep spark plug hole, so the adapters on my compression tester would not fit down inside the space. My solution was to find a threaded bung that fit my tester, break the top off a spark plug and drill the core out, the weld the threaded bung to the spark plug body. Now it was high enough in the spark plug recess that I could slap the tester on top. Having a welder really is a game changer. :Cool:

    Jose
     
  4. VFR4Lee

    VFR4Lee Member

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    I would think you could turn the engine by hand.
    Does not have to turn fast, does it?
    With a big ratchet. Maybe?
     
  5. FJ12rydertoo

    FJ12rydertoo Member

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    If the throttle bodies are mounted you'll need to make sure the butterflies are open too. Yeah, turning it by hand won't give you an accurate reading.
     
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