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Thread: Both heads taken off at 200,000 Ks. Do rings too ?

  1. #1

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    Default Both heads taken off at 200,000 Ks. Do rings too ?

    I've just taken off both cylinder heads from my TJ Magna.....a 2000 model Solara. The reason is that it overheated whilst towing a trailer and burnt a couple of valves...a compression test showed this.

    I think my radiator was clogged up for some obscure reason. I won't go into this part right now....I have described it on another thread a few months ago and when I get the radiator flow tested I will post the results on that thread.

    I will of course get the cylinder heads fixed at a reconditioners.

    My question is this : while I am at it all, should I replace the rings ? The car has done 200,000 Ks, but it is a very strong V6 motor.
    There is a rule of thumb that engine reconditioners have, whic is : "replace rings before big ends". So perhaps I should. I am hoping to do another 100,000 Ks in it.

    As I'm 62, over the years I have rebuilt a fair few 4 cylinder engines and have the gear : torque wrench, ring compressor and so on....but I've never done a V6. But the heads are now off and I'm scratching my head about whether to do the bottom end.

    If I take off the sump, is it relatively easy to pop the pistons out when I have the heads off ?
    I have borrowed a workshop manual, but it's always better to get this info from real people.

    I remember rebuilding a friend's 1991 four cylinder Magna about 10 years ago, and it wasn't a pleasant job. There were balance shafts that made it more complex.

    At the time, a mechanic mate told me to just buy a secondhand engine, because that was what he usually did with Magnas. He said they were too much trouble to recondition properly and even then the result was not guaranteed.
    However this car I'm doing now is of course a different beast.

    My second question is this : as the valve stem seals are most likely what caused my excessive oil usage (and this is a known fault in Magnas), is there a known good brand to buy ? Or have Mitsubishi confessed to the sin of having fitted poor quality ones and now supply good quality ones ?

  2. #2

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    Do you mean just replace the rings without any honing etc?

    From what I understand these engines last forever and at 200,000km it is unlikely that your rings are bad.
    In fact 400,000km doesn't even seem to be much for these engines.

    Personally I'd consider replacing the whole motor rather than doing heads and pistons especially with a 6G75

  3. #3

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    No, I didn't mention anything about not honing the bore.

    I'm just wondering how long the bottom end lasts on these engines. I have to make a call about whether to do the rings while I have got the cylinder heads and so much peripheral stuff taken off.

    I've heard they are strong engines, but 200,000 Ks is a lot. Plus the oil usage had me worried for some time, but from all indications it is a valve stem seal problem.

  4. #4

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    My TH Magna had covered 490,000 when I sold it last year. It was perfect, no rattles, minimal oil consumption. Only issue was some weeping from the rocker covers. You don't need to touch the bottom end or rings for that matter.

  5. #5

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    I have 250,000km on my 6G74 and after replacing the valve stem seals the oil level stays the same after 10,000km

  6. #6
    RonRabbit99's Avatar
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    Quote Originally Posted by Latindancer View Post
    I've just taken off both cylinder heads from my TJ Magna.....a 2000 model Solara. The reason is that it overheated whilst towing a trailer and burnt a couple of valves...a compression test showed this.

    I think my radiator was clogged up for some obscure reason. I won't go into this part right now....I have described it on another thread a few months ago and when I get the radiator flow tested I will post the results on that thread.

    I will of course get the cylinder heads fixed at a reconditioners.

    My question is this : while I am at it all, should I replace the rings ? The car has done 200,000 Ks, but it is a very strong V6 motor.
    There is a rule of thumb that engine reconditioners have, whic is : "replace rings before big ends". So perhaps I should. I am hoping to do another 100,000 Ks in it.

    As I'm 62, over the years I have rebuilt a fair few 4 cylinder engines and have the gear : torque wrench, ring compressor and so on....but I've never done a V6. But the heads are now off and I'm scratching my head about whether to do the bottom end.

    If I take off the sump, is it relatively easy to pop the pistons out when I have the heads off ?
    I have borrowed a workshop manual, but it's always better to get this info from real people.

    I remember rebuilding a friend's 1991 four cylinder Magna about 10 years ago, and it wasn't a pleasant job. There were balance shafts that made it more complex.

    At the time, a mechanic mate told me to just buy a secondhand engine, because that was what he usually did with Magnas. He said they were too much trouble to recondition properly and even then the result was not guaranteed.
    However this car I'm doing now is of course a different beast.

    My second question is this : as the valve stem seals are most likely what caused my excessive oil usage (and this is a known fault in Magnas), is there a known good brand to buy ? Or have Mitsubishi confessed to the sin of having fitted poor quality ones and now supply good quality ones ?
    I replaced the valve stem oils seals in my TJ at 250k with ones I bought from Rockauto - now minimal to nil oil consumption (now at 270k).
    Been into cars for too long

    '72 LC Torana, '76 TD Cortina, '85 XE Falcon, '84 E15 ET Turbo Pulsar, '96 CC Lancer, '99 TH Magna (Current), 2011 SZ Ford Territory (Current)
    '01 TJ Magna (for my son)

  7. #7

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    Well, it seems that the bottom end really lasts on these engines. I will just do the heads then.

    I must say I'm disappointed with the valve stem seals though. They are a known weakness and my car has been using a lot of oil since I bought it (in seemingly pristine condition) at 118,000 Ks. I hope the oil usage is due to them.....the symptoms seem to fit.

    I'll put new gaskets in the rocker covers and use the highest gasket-grade silicone too.

  8. #8

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    Aug 2014
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    Quote Originally Posted by Latindancer View Post
    Well, it seems that the bottom end really lasts on these engines. I will just do the heads then.

    I must say I'm disappointed with the valve stem seals though. They are a known weakness and my car has been using a lot of oil since I bought it (in seemingly pristine condition) at 118,000 Ks. I hope the oil usage is due to them.....the symptoms seem to fit.

    I'll put new gaskets in the rocker covers and use the highest gasket-grade silicone too.
    According to advice from many posters on this forum - DO NOT USE ANY ADDITIONAL MATERIAL WHEN REFITTING NEW ROCKER GASKETS.

    Plese especially note corroborating information from "Madmagna" in post #21 Page 3 and post #34 on page 4 of the following thread:

    http://www.aussiemagna.com/forums/sh...t=58812&page=3
    Last edited by leadfoot6; 13-07-2018 at 06:31 PM.

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