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Thread: Disco 1 3.9 V8 motor. Rebuild or not?

  1. #1
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    Disco 1 3.9 V8 motor. Rebuild or not?

    OK folks, the time has come where I might be able to gather enough time to get the old girl going again. I know the head gaskets need replacing as she is loosing water without any obvious leaks.

    So, if I'm going to be doing the work, is it worth doing a complete rebuild?

    She's done a little over the 200K mark. At the very least, I will replace the head gaskets (and any other gaskets that need replacing), check (and fix/replace) the cam system and a general clean and check of all accessible components. I'll also be getting all the injectors properly cleaned. However, if there is any chance that something like the bearings might fail or wear out in the near future I'd rather do the whole lot in one go. That way I would know that I have a fully reconditioned motor.

    Also, where is the best place on the Gold Coast to get the bits?

    Any thoughts would be appreciated.

  2. #2
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    It's really not possible to answer your question until you know more about what is wrong with the engine.

    The water usage could simply be head gaskets but also could be a slipped sleeve which would necessitate a complete disassembly of the engine.

    If it is just head gaskets, then the bearings etc should be good for hundreds of thousands of ks , and all that is needed is what is called a "top overhaul".

    If it is slipped sleeves then seeing the engine is in bits , it would be prudent to replace all the bearings and rings.

    You should also make sure to have the heads serviced as the valves are pretty leaky by 200K.

    You should not limit yourself to the gold Coast for parts as there are many sellers who will courier top overhaul kits to you on Ebay or elsewhere.
    Regards Philip A

  3. #3
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    Thanks Philip

    It is possible that I have a slipped sleeve, as she did overheat a lot when I was on Fraser. Would it be prudent to start out with the top end to see if there is a slipped sleeve, then pull the motor out if there is.

    Also, could you recommend a supplier or kit?

    Thanks

  4. #4
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    PM sent
    Regards Philip A

  5. #5
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    OK, I've spent some time attacking the heads. Turns out to be quite a big job anyway.
    I did a compression test just before I took the rocker covers off. Seems that no 7 has low compression. Figures are as follows (taken with engine cold):

    1 - 155
    2 - 160
    3 - 145
    4 - 165
    5 - 155
    6 - 160
    7 - 77
    8 - 165

    Seems alright for the most part. No 7 is obviously going to be the one I'm concentrating on, so that head had to come off first. Wasn't too difficult once I purchased a new (half decent) socket after mine broke, and a 600mm breaker bar.

    I can't see any obvious signs of head gasket leakage on the cylinder (See attached pictures), so I'm getting a little worried.

    With the other head, I can't get the bolt closest to the bulkhead off. Just can't seem to get enough grip and it keeps slipping. So now I think I'm going to have to pull the motor anyway. Probably going to need to use an impact wrench to get that one off as I think I've rounded it a bit.

    Any tips on pulling the block out?



    These pics are of no 7 cylinder:
    With gasket still on


    With gasket off:


    On the head:

  6. #6
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    Tips for head bolt: Buy an impact socket with only 6 sided hex, then use a universal or similar joint to get it.

    I just did an engine swap, documented here:

    Fitting a '92 3.9 RRC motor into a '94

    You need to look at no. 7 cylinder at more of an angle, to see if the liner is down compared to the others, and to see if the top compression ring has been contacting the bore all the way around. The engine I just pulled had no. 8 liner down about 1mm compared to all the others.

    Attached Images Attached Images

  7. #7
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    Thanks bee utey, your post looks like it will be useful.

    I don't think the sleeve has slipped, but will check again.

    I tried a universal joint, but ended up twisting it nearly to braking point. These bolts are really tight, which it why I needed the 600mm breaker bar. My first attempt resulted in my socket splitting, probably a cheapo one so bought a Sidchrome one as nothing else was available yesterday (they didn't have any impact sockets in stock@#$#@!). The Sidchrome one has not broken yet, but is showing signs of wear already at the ends of the teeth.

    I'll pick up an impact socket this week and give it another go.

  8. #8
    Alec Guest
    Little Red, this is a VERY comon problem on the 3.9, plenty write-ups on the net. Best fix is to replace the liners with T-top liners. I had a 3.9 re-lined with Isuzu liners and it worked a tread, just remember to use the cast iron sleeves and not the chromed ones. The cast ones can be bored to the 94mm (?) so no need to replace pistons.

  9. #9
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    Hmmm, I didn't realize they were Isuzu, I thought they might have been aftermarket ones. Where would be a good place to get something like this?

    Guess I'll also have to find someone to machine it for me. Can anyone recommend someone on the Gold Coast?

  10. #10
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    My advice is if you're spending on a T-top liner conversion rather upgrade to a 4.6 while you're busy............

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