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Thread: Head Gasket Replacement

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    george light
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    Head Gasket Replacement

    Hi, Fairly certain my Legnum's head gasket has failed. So I intend on changing it soon but was just wondering how difficult of a job its, mostly concerning the rear bank. Is there enough room to remove the head without having to move the engine? Also, as the reason for its failure was overheating, im going to get the head skimmed as well.

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    Nick Mann's Avatar

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    There are a lot of coolant pipes in the engine bay and a small leak in a pipe will give similar symptoms to a failed head gasket.
    Most head gasket failures (and there aren't many) are down to running high boost on standard stretch head bolts. @Davezj has done this job I think? My memory is that the rear head does come off with the engine in the engine bay but it is awkward at best.

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    One of the coolant pipes split while I was driving and it overheated before I noticed and stopped. I haven't done any turbo mods yet or turned the boost up. I've tested the coolant for exhaust gases and it shows that there are exhaust gases present. I could also do a compression test to be sure, but at the moment a head gasket change is looking likely.

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    Nick Mann's Avatar

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    Okay, fair enough. It sounds like you could well be right. Hopefully Dave will be along soon to confirm how bad or good my memory is.

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    Davezj's Avatar

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    I have done head gesket replacements on the 6A13tt engines.
    engine out is a much easier way to do it.

    unfortunately in both of the engines i have done the head gaskets on, once the engine was out and the bearings were checked it was found they needed replacement.
    so what was originally a head gesket job it turned into a full engine rebuild.

    you can take the rear head off the engine while it is in the car, but would not both it is more hassle than it is worth.
    just drop the engine and gearbox and transfer case out the bottom of the engine bay and lift the front of the car up so you can slide the engine gearbox combo out from under the car.

    it all depends on what land/ground you have have to do the engine removal on. flat open space off the road is always good.

    Bye for Now!

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    Thanks for the reply. I suppose I'll go with the engine out route if its easier. Maybe I'll do a few other bits on it while its out. Also, on an unrelated note just so I don't have to start a new thread for one question, how much power can the Auto box's take reliably?

  7. #7
    Davezj's Avatar

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    i have been running 320hp plus for the last 10 years and it easily handles this. i had 320hp on 1.1-1.2bar boost pressure.

    the reason i had 3 engines with head gasket fails is because i run the turbos with with no wastegate pipes connected so they boost as hard and as fast as they can.
    full boost 1.6bar at 2500-3000rpm.
    massive torque very low down in the rev range is lots of fun to play with, but it will lift the heads if you have standard head bolts.

    my point is i have not dynoed my car since running max boost but it will give more than 320hp in short bursts until things over heat in the inlet air department.
    i have been running like this since i rebuilt my fist engine 20K miles ago with stronger head bolts and so far this has fixed the high boost head lift issue the 6A13tt engine seems to have with standard head bolts.
    My auto box is still going strong and launches hard every time.
    put it in D and 2500rpm foot hard on the brake. wait for the lights to changes and lift off brake and plant the throttle for a perfect launch every time.
    basically i have abused my auto box for years and it is still ok. all i can say is, i use amsoil ATF in it.

    after saying all this i do have to add that there seems to be some different versions of the auto box some have stronger parts in them than others.
    i think it is the second gen box that has the weaker parts in it. i think it has the EB on the end of the model number. i can't be sure off the top of my head.
    you will have to check and verify this for yourself, it is all documented on these forums pages somewhere.

  8. #8

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    Thanks for your help Dave. Mines a 96 Legnum so hopefully that means its the stronger one. Will find out though.

  9. #9
    Davezj's Avatar

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    the original auto boxes were pretty good.
    that is what i fitted along with the correct ecu after my second gen box got trashed after a heavy launch.

    never had an issue with the auto box since
    I must have 100's of launches on the auto box, pre and post engine rebuild, with high boost, high torque at low rpm.
    the above launches are also a good way to trash conrod and crank bearings. especially if you use crap engine oil. never go cheap on engine oil or ATF.

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