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Location:
Lismore, NSW
Registered:
February 2003
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7MGTE Headgasket
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Mon, 12 April 2004 10:43
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Hey, I finally got my Supra on the road but I am concerned that im leaking compression into the cooling system why I say this is when I start the motor up I get pressure straight up in the radiator. I am not leaking water into the oil or viceversa. I am using a Copper head gasket and O-ringed block. Why is this happening, the only thing I can think of is that there could be a small gap between the two ends of a or all of the O-rings. Ill be pressure testing each cyclinder tomorrow but I just want any suggestions regarding my problem.
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Location:
Perth
Registered:
January 2003
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Re: 7MGTE Headgasket
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Tue, 13 April 2004 07:24
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It's not possible for us to diagnose your problem over the internet! I would do a leakdown test on each cylinder to check sealing and go from there.
Can I ask how much the parts and machining were to o-ring the block? I am considering going down that road. Also, did you use a copper head gasket sealant during assembly?
Good luck! and be careful to ensure that your coolant does not become corrosive, I have several 7M heads that are no longer usable due to corrosion in the water jackets.
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Location:
Lismore, NSW
Registered:
February 2003
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Re: 7MGTE Headgasket
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Tue, 13 April 2004 09:46
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Ok I compression tested it with a very pleasing 150psi in all cyclinders BUT... I pressure tested each cyclinder by connecting a compressor up to it and filling the chamber up with compressed air, on every account my radiator started to overflow. *$%* What to do? If I decide to get a HKS MHG do you need O-rings? Or can i leave them out. Considering the block is oringed already but could be causing the above problem. What to do?
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7MGTE Headgasket
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Tue, 13 April 2004 10:13
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if its o-ringed, you need to keep running the o-rings with the copper head gasket. did you use hylomar on the copper before installing?
id be getting a gas analysis done on the radiator.
as for your method of checking combusion pressure, not exactly the way to do it. just see if you can get a proper gaugue and crank the engine over 
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Location:
Lismore, NSW
Registered:
February 2003
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Re: 7MGTE Headgasket
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Tue, 13 April 2004 10:31
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Hey ed, I used a guage and cranked it to get my compression figures. I used the compressor to see if it would pressurise the radiator when compressing the air in each cylinder. I used hylomar spray on the gasket when installing it. What I think is that between the two ends of the orings there might be a small gap, could that be the reason why its blowing into the water jackets? If I do go for a HKS MHG do I have to put the orings back in or what would you do in this case? Cheers
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Location:
Melbourne
Registered:
May 2002
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Re: 7MGTE Headgasket
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Tue, 13 April 2004 10:56
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a gap between the ends of the O rings is a HUGE problem no way would it seal! i would get some more wire and file the ends until its PERFECT other then that i would chuck a stock gasket in and hope the O ring grooves in the block help rather then hinder the stock gasket hold!
Allan
P.S i run a stock gasket on a poorly tuned 13psi runing 110,000km old un-surfaced block with arp studs and its still holding after almost 20,000 km of abuse!
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I Supported Toymods
Location:
melbourne.vic.au
Registered:
May 2002
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Re: 7MGTE Headgasket
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Tue, 13 April 2004 11:24
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| Allan wrote on Tue, 13 April 2004 20:56 |
...
P.S i run a stock gasket on a poorly tuned 13psi runing 110,000km old un-surfaced block with arp studs and its still holding after almost 20,000 km of abuse!
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I can concur  if needed in regards about the engine anyway 
Sounds like you have BHG, I had one 1 year ago with your symtoms and got the gasket replaced though mine was a stock gasket for my 5M-E, and now I have BHG between 2 cylinders (5M-E again  )...
Chers.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7MGTE Headgasket
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Tue, 13 April 2004 14:37
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i wouldnt put a laminated steel headgasket anywhere near a block or head that has been machined for o-rings... whats the headgasket going to bite into? the whole point of the o-ring is to have a ring of high clamping pressure, without it, what chance does a steel h/g have?
yes, id assume a gap would be significant. surely the rings were made so there was no end gap when installed properly?
doesnt 'quite' explain why every cyl is communicating with a water gallery, but its a start. like i said, id be getting a radiator gas analysis done before i thought any harder about whats going on
cheers
ed
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Location:
Lismore, NSW
Registered:
February 2003
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Re: 7MGTE Headgasket
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Wed, 14 April 2004 10:40
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Hey, Ive spoken to a few people and they have all suggested using a stock HG with out the orings. Hopefully as allan said that the grooves might assist and not hinder it. Ill chuck a stocko in and clamp it down to about 78lbs and see how it goes. Its about a days work to do a headgasket if it does blow. Fingers crossed.
Ed, When I got the block Oringed they did the grooves for me but with the actual orings they only supplied me with a roll of wire which I had to bend into the rite shape and also cut the wire to the rite length, as it being my 1st time I thought I did everything rite. Guess not 
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Location:
Lost in the K hole
Registered:
May 2002
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Re: 7MGTE Headgasket
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Wed, 14 April 2004 13:08
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if youre going to get a new gasket, id go straight to a mhg (hks/turd etc)... $230 from penrith toyota. having an organic comound will suffer. but im still of the opinion that having a machined recession in the block where the headgasket fire ring will ultimately bite is a BAD thing... why not just redo the o-rings and refit another (new) copper head gasket? cheaper than the mhg, and perhaps even a $180 stocker
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Location:
Lismore, NSW
Registered:
February 2003
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Re: 7MGTE Headgasket
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Thu, 15 April 2004 09:43
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Hey, I was told by Dave (cambelt) that the face of the block and head both have to be dead flat with no machine marks in it for a MHG. I have had both surfaced but only good enough for a std HG. Dont want to go another copper HG after chatting to dave about it and a few other people. I will still look into the HKS gasket anf find as much info as I can about it.
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Location:
Perth
Registered:
January 2003
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Re: 7MGTE Headgasket
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Fri, 16 April 2004 04:16
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Did you braze the wire ends to form unbroken rings?
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Registered:
July 2002
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Re: 7MGTE Headgasket
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Fri, 16 April 2004 15:39
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20,000 km out of a 7MGTE!!!!
Thats incredible......
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Location:
Melbourne
Registered:
May 2002
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Re: 7MGTE Headgasket
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Fri, 16 April 2004 15:55
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| Anthony Kellam wrote on Sat, 17 April 2004 01:39 |
20,000 km out of a 7MGTE!!!!
Thats incredible......
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On top of the other 100,000km its allredy done, i take it you own a 1jz? how many km on the clock of that?
Allan
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Registered:
July 2002
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). I dont know if the whole odometer mech gets changed as well but I presume it does.