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 Post subject: 7mge losing coolant at high speeds
PostPosted: Wed Jun 05, 2013 7:16 pm 

Joined: Sun Mar 17, 2013 5:04 pm
Posts: 35
Location: Edmonton, Alberta
quick 7M question, albeit i know the headgasket issue has been beaten to death

ive got a 1991 Crown with 7MGE, 93,000km. a few weeks ago i took it on the highway. 2 hour round trip, went about 160kmh at 4000rpm the whole way. after i got home, the coolant reservoir was empty and the rad was half full.

i thought the valve in the rad cap maybe went bad and stuck open causing coolant to blow out the reservoir, old cap was from when the car was in Tokyo so around 10 years old. put a new cap and thermostat in, went on the same highway last week going 170kmh there and when i got there, the reservoir was full of coolant, overflowed coolant allover the frame, and the rad was down about a quarter liter. so i filled it up again before i went home. when i went home i drove only 130kmh, lost no coolant from the radiator and the reservoir never overflowed and the level stayed in the correct area

car doesnt overheat ever, only floods the reservoir if i go faster than 150kmh. no leaks, oil is clean, blows a bit of white exhaust only on cold starts but no sweet smell, pulls fine all the way to redline. im at a loss, only thing i can think of is the headgasket is just starting to go and combustion gas when i go that fast is flooding coolant into the reservoir. plausible or could it be something else? knowing 7Ms i keep jumping to it being the headgaket

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 Post subject: Re: 7mge losing coolant at high speeds
PostPosted: Thu Jun 06, 2013 6:43 pm 
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Joined: Sun Jun 01, 2008 11:12 pm
Posts: 376
Location: Torrance CA
Yup I would bet it's the headgasket

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 Post subject: Re: 7mge losing coolant at high speeds
PostPosted: Thu Jun 06, 2013 8:10 pm 

Joined: Sun Mar 17, 2013 5:04 pm
Posts: 35
Location: Edmonton, Alberta
robakun wrote:
Yup I would bet it's the headgasket


boo, just gonna tear down the engine in August and do the timing belt at the same time then. thought maybe being low mileage it wouldnt be HG but i guess 7MGE hold no prisoners

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 Post subject: Re: 7mge losing coolant at high speeds
PostPosted: Fri Jun 07, 2013 12:33 pm 
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Joined: Mon Apr 18, 2011 8:47 am
Posts: 274
Location: TX
rebuilding it is asking for the same thing to happen sooner or later. no combination of studs/gaskets is going to help that for very long. instead of wasting the cash on machining and parts and labor, maybe find a better powerplant. :tu:

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 Post subject: Re: 7mge losing coolant at high speeds
PostPosted: Fri Jun 07, 2013 4:38 pm 

Joined: Sun Mar 17, 2013 5:04 pm
Posts: 35
Location: Edmonton, Alberta
lolumad wrote:
rebuilding it is asking for the same thing to happen sooner or later. no combination of studs/gaskets is going to help that for very long. instead of wasting the cash on machining and parts and labor, maybe find a better powerplant. :tu:


ive spent the last while reading hundreds of threads on MKIII Supra sites, consensus is if you have a low mileage engine and its just starting to go you can retorque the OEM head bolts to 70ftlbs and maybe have to not do the gasket. otherwise replace the gasket and torque the new head bolts to 70ftlbs and it should be the last time you need to do the headgasket. if im going in there im doing everything though, im a mechanic so i can do this all myself easy. head shouldnt be warped at all because it hasnt overheated so doubt it needs machining

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 Post subject: Re: 7mge losing coolant at high speeds
PostPosted: Sun Jun 09, 2013 2:59 pm 
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Joined: Sun Jun 01, 2008 11:12 pm
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Location: Torrance CA
lolumad wrote:
rebuilding it is asking for the same thing to happen sooner or later. no combination of studs/gaskets is going to help that for very long. instead of wasting the cash on machining and parts and labor, maybe find a better powerplant. :tu:


The 7M is an great engine. No need to replace it. Just build it back up with the appropriate precautions for the head gasket and you will be fine for a long time.

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 Post subject: Re: 7mge losing coolant at high speeds
PostPosted: Mon Jun 10, 2013 1:05 pm 
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Joined: Mon Apr 18, 2011 8:47 am
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Location: TX
haha. you guys keep believing! sounds like there's plenty of hearsay and consensus from mkiii supra sites, so i wont waste your time with evidence to the contrary provided in detail by a guy who devoted pretty much the last 20 years to this specific engine.

like, figuring out a solution for the oil starvation issues that come about as a result of the design.

or the other reasons why the head gasket might/can/will fail prematurely?

i'm just saying: add up the cost of a rebuild kit, the labor (time you spend personally or time you pay someone else to tear it down and put it back together), factor in the odds of something else going wrong right after you get it running again... then think about spending that money and time putting in a more powerful, more efficient engine.

for a lot of people, the solution to that equation is obvious. to others who want to stick with the M for sentimental reasons, understand that it comes with its share of flaws and it will cost you more for less of a benefit over the years.

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 Post subject: Re: 7mge losing coolant at high speeds
PostPosted: Mon Jun 10, 2013 8:15 pm 

Joined: Sun Mar 17, 2013 5:04 pm
Posts: 35
Location: Edmonton, Alberta
odds of something not running would be worse with swapping in a JZGTE engine, that and i dont think a A340E would take well to JZ power. then its the headache of swapping in a R154, too much for a daily driver. my Supra already never runs lol. HG kit with seals is 500 bones and at least i still have a low mileage engine that hasnt been bagged on. labor is no biggie, if its indeed bad just gonna take 2 extra vacation days this summer to do it

what else can go up with 7M? everywhere ive read where people had the HG go around 100,000km, many of them replaced the gasket and torqued it to 70ftlbs and the cars at 400,000km with no problems.

i havent been on the highway since, but ive replaced a few things. gonna give it one more chance before i tear it down

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 Post subject: Re: 7mge losing coolant at high speeds
PostPosted: Tue Jun 11, 2013 9:44 am 
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Location: TX
why are you thinking GTE is the only JZ option out there? same auto transmission came on GE motors and is extremely common, no need for a manual swap.

i'm not going to continue to argue the point but i will present factual info to clear up any misconceptions you might have. the biggest probs i foresee would be wiring if your current engine/body harnesses are significantly different and you can't get an EWD and possibly mounts unless oem or aftermarket jzs/jzz/jza/jzx could work with your crossmember.

but tbh, i'd skip jz entirely and go uz if i had a crown as cool as yours 8)

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 Post subject: Re: 7mge losing coolant at high speeds
PostPosted: Tue Jun 11, 2013 11:38 am 

Joined: Sun Mar 17, 2013 5:04 pm
Posts: 35
Location: Edmonton, Alberta
no not arguing lol, but everywhere ive read that the only reason 7MGE blow HG unless you severely overheat it like any other engine is Toyota undertorqued the headbolts. just Toyota never admitted to it. im used to owning Nissans where HG are not as often as a problem

1UZFE would scare me more, this thing is already a $80 tank of gas once or twice a week

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 Post subject: Re: 7mge losing coolant at high speeds
PostPosted: Fri Jun 21, 2013 11:57 am 

Joined: Sun Mar 17, 2013 5:04 pm
Posts: 35
Location: Edmonton, Alberta
so it ended up getting worse and blowing sweet clouds of white coolant. definitely headgasket. i was going to tear into it but my father passed away a few days ago and i dont want to really deal with the car so i dropped it off at a tuning shop. passed a Co2 test at idle, but failed under load so the headgasket is definitely bad. said from past experience, the head could be decked and the engine might need a whole rebuild. or i might have noticed it early enough that its not that bad, head is coming off today or Monday. estimate for a complete engine rebuild is scary but what can you do, i just want a reliable car again in the end

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