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Discussion Starter · #21 ·
Worst case scenario, 2005. Those things were plentiful back then. :)

Realistically speaking though, it's a solid deck, iron block engine. As others have pointed out, the head is more of a concern. It can be repaired if not level, at a machine shop, but the hardness of the head may be an issue if it got too hot.

As Doug points out, data is your friend here. Throwing parts at a problem without knowing what the problem actually is can be a great way to lighten one's wallet. In the case of the 1984 6M P-Type Mk2 I picked up in 2008, I had overheating issues. Started with replacing the cheap stuff, working on it and replacing parts that got progressively more expensive. Unfortunately in my case, it turned out to be a bad radiator. On the plus side, by the time the testing reflected that (because it was the only cooling system piece left) I had a fully new cooling system that gave me years of trouble free performance.
Thanks for the input! I'm not very worried about the block now. My suspicion is currently the head gasket. When I get home from college I'm going to use a coolant exhaust gas tester to see if it's the hg. If not I'm going to go sleuthing in the coolant system. The reason I was so eager for a rebuild is because I have been itching to through some wiseco pistons and new rods into it for a while now, so it made sense in my head. I now realize that I should address any problems with the engine or cooling system first. It would be a mistake to rebuild an engine, and then not have adequate cooling.
 

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I now realize that I should address any problems with the engine or cooling system first. It would be a mistake to rebuild an engine, and then not have adequate cooling.
Smart move! Remember too, that a head gasket can fail in a few ways:

-Between the combustion chamber and the coolant passage of one or more cylinders. This will be detected by your gas tester, or a really high pressure in the cooling system. Coolant tends to get pushed out of the overflow a lot when this happens. Had this happen on one of my HG failures, not fun, but it's arguably better than...

-Between the coolant and oil passages. Would be a strange thing for this to happen, methinks. If you mix the coolant and oil, the result is an acidic nastiness (commonly referred to as milkshake) that will eat your rod bearings. You'll know when this has done it's thing. Knock knock... Check the underside of your oil cap. If it looks like a chocolate milkshake, you have some work ahead of you, and the sooner the better.

-Between the combustion chamber and oil passage. I don't think I've had this one happen to me. I would think it would start burning oil? Combustion pressure is gonna be higher than oil pressure at the top of the piston stroke, but during intake and exhaust phases of the cycle, I'd think it would be sucking oil into the cylinder with the failed gasket. Lots of blue smoke if this is the case.


Also, really random question, but your avatar looks like the host of Forgotten Weapons. Love that show.
 

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Discussion Starter · #23 ·
Smart move! Remember too, that a head gasket can fail in a few ways:

-Between the combustion chamber and the coolant passage of one or more cylinders. This will be detected by your gas tester, or a really high pressure in the cooling system. Coolant tends to get pushed out of the overflow a lot when this happens. Had this happen on one of my HG failures, not fun, but it's arguably better than...

-Between the coolant and oil passages. Would be a strange thing for this to happen, methinks. If you mix the coolant and oil, the result is an acidic nastiness (commonly referred to as milkshake) that will eat your rod bearings. You'll know when this has done it's thing. Knock knock... Check the underside of your oil cap. If it looks like a chocolate milkshake, you have some work ahead of you, and the sooner the better.

-Between the combustion chamber and oil passage. I don't think I've had this one happen to me. I would think it would start burning oil? Combustion pressure is gonna be higher than oil pressure at the top of the piston stroke, but during intake and exhaust phases of the cycle, I'd think it would be sucking oil into the cylinder with the failed gasket. Lots of blue smoke if this is the case.


Also, really random question, but your avatar looks like the host of Forgotten Weapons. Love that show.
Yeah my avatar is Ian McCollum LOL,

So I highly doubt the failure would be between the coolant and oil chambers, as I have checked and changed the oil, and it was pristine. On that note the car has not appreciably burned any oil so I do not suspect it happened between the combustion chamber and oil passage. The car has a 3 inch cat-back exhaust system for what its worth, and I havent noticed any color smoke, be it white from coolant or the bluish oil smoke. Coolant was being forced into the overflow tank when the car overheated so my money is on a combustion chamber/coolant passage leak.

Off topic of the post but the previous owner has installed a fair amount of aftermarket parts, particularly to the intake and I'm having trouble identifying the products. Could anyone point me to a good resource for that?
 

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Discussion Starter · #24 ·
Yeah my avatar is Ian McCollum LOL,

So I highly doubt the failure would be between the coolant and oil chambers, as I have checked and changed the oil, and it was pristine. On that note the car has not appreciably burned any oil so I do not suspect it happened between the combustion chamber and oil passage. The car has a 3 inch cat-back exhaust system for what its worth, and I havent noticed any color smoke, be it white from coolant or the bluish oil smoke. Coolant was being forced into the overflow tank when the car overheated so my money is on a combustion chamber/coolant passage leak.

Off topic of the post but the previous owner has installed a fair amount of aftermarket parts, particularly to the intake and I'm having trouble identifying the products. Could anyone point me to a good resource for that?
Also sorry if I seem somewhat unfamiliar with engine layout. I'll post a picture but there are several mods that the previous owner installed, so I'm somewhat unfamiliar with what the stock parts look like or where they are located. For example, he installed a hks bov, so I have no idea where the stock bpv bolts on or what it looks like for that matter.
264089


For all wondering about the rat's nest of wires to the right, that's a fan control module the last owner installed. As far as I'm aware, its simply used to run the fans for several minutes after shutoff. It's one of many electrical/wiring nightmares the last guy left me, though they are mostly located outside the engine bay.

Again, I thank you guys for your patience. I've only taken on working cars in the last 4 years of my life, and I have only learned how by reading, watching videos etc. I never had a real instructor or training. I realize that makes me sound rather incompetent, and I'd like to think I'm not. I've successfully taken on some pretty ambitious projects and repairs before, so I'd like to think I'm not fully incompetent, but I recognize that there are most definitely gaps in my knowledge. I never received any real training or instruction, and lack the years of experience y'all do. I guess I'm just trying to say I appreciate you guys' help and to have a little bit of patience.
 

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One thing you can do when looking for a HG leak between combustion and coolant (which it sounds like you have) is to pull the spark plugs. If coolant is going from combustion to coolant, when you shut it down, coolant will usually migrate into the cylinder as now it's 14psi and the cylinder pressure will vary between a strong vacuum, a strong psi, or neutral. A clean plug means it is getting steam cleaned with coolant and another sure sign and helps ID the cylinder as well.
 

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Discussion Starter · #26 ·
One thing you can do when looking for a HG leak between combustion and coolant (which it sounds like you have) is to pull the spark plugs. If coolant is going from combustion to coolant, when you shut it down, coolant will usually migrate into the cylinder as now it's 14psi and the cylinder pressure will vary between a strong vacuum, a strong psi, or neutral. A clean plug means it is getting steam cleaned with coolant and another sure sign and helps ID the cylinder as well.
I never would have thought of that. The more you know. If its any help, I also have a bore scope that I used to inspect diesel injector ports, and occasionally look at the cylinders on my LS. Would the same steam cleaning effect be visible on the piston surface?
Also what coolant do you use? Mine is still running the old green IAT stuff, but I've read that some people on the forum use the Toyota red OAT without issue. Its kind of hard to source the old stuff locally, would you recommend I make the switch?
 

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Again, I thank you guys for your patience. I've only taken on working cars in the last 4 years of my life, and I have only learned how by reading, watching videos etc. I never had a real instructor or training. I realize that makes me sound rather incompetent, and I'd like to think I'm not. I've successfully taken on some pretty ambitious projects and repairs before, so I'd like to think I'm not fully incompetent, but I recognize that there are most definitely gaps in my knowledge. I never received any real training or instruction, and lack the years of experience y'all do. I guess I'm just trying to say I appreciate you guys' help and to have a little bit of patience.
I'll leave the 7m aftermarket part identification to those with more familiar eyes than mine, I haven't had a 7m in well over a decade.

As for your experience, don't sweat it! Plenty of us have informal education, or we've gone to the School of Hard Knocks. I have a degree or two from there myself haha. It's good to have confidence in yourself. I realized at a certain point that God gave me two hands just like most everybody else. A set of basic tools, dedication, desire to learn, a good community around these cars, and I was well on my way to learning far more than I ever would have thought about not only Supras, but cars and mechanical things in general.

Always, always, always be willing to step back and admit you don't know or don't understand something. Keeping humble might be the difference between a car that's still not cooperating and a car that's blown up due to overconfidence or simple ignorance. We're happy to help if you're happy to stay humble and learn to ask questions in a helpful manner. Some of the very best posts I've seen on here seeking help had the following:

-What the car is doing
-What conditions it was doing this under
-Driver inputs and car's outputs
-What the poster had done in regards to diagnosis
-What repairs / modifications have been made recently

Good input, good output. ;)

I never would have thought of that. The more you know. If its any help, I also have a bore scope that I used to inspect diesel injector ports, and occasionally look at the cylinders on my LS. Would the same steam cleaning effect be visible on the piston surface?
Also what coolant do you use? Mine is still running the old green IAT stuff, but I've read that some people on the forum use the Toyota red OAT without issue. Its kind of hard to source the old stuff locally, would you recommend I make the switch?
Yes, coolant in the combustion chamber has a steam cleaning effect on the piston as well. Consider how hot a combustion chamber is, coolant doesn't stand a chance! Pull those plugs, stick that bore scope in there (heck even a flashlight will do if the piston is near the top of its stroke), and take a look. If they're silver on top, ding ding ding... you found a BHG. Normal pistons will have a bit of carbon buildup, will looks brown to black, hopefully somewhat uniformly.

As for switching coolant, this is fine to do, however I'd caution you to REALLY REALLY REALLY flush it out. Different coolants have different chemical makeups, and don't always play well with one another. If I recall mixing green and red coolants can form a sludge of some sort, though the chemistry behind why I've forgotten. Either way, clogged cooling systems is a good way to cause an engine to run hot. I seem to recall running an engine with no thermostat, one end with a garden hose (or if you prefer, a lot of distilled water, like... a LOT, probably 10+ gallons at least), the other end open to flush out all the old coolant. Don't forget to have the heat on full blast and / or manually open the heater valve on the firewall to get all that coolant flushed out too.
 

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Discussion Starter · #28 ·
I'll leave the 7m aftermarket part identification to those with more familiar eyes than mine, I haven't had a 7m in well over a decade.

As for your experience, don't sweat it! Plenty of us have informal education, or we've gone to the School of Hard Knocks. I have a degree or two from there myself haha. It's good to have confidence in yourself. I realized at a certain point that God gave me two hands just like most everybody else. A set of basic tools, dedication, desire to learn, a good community around these cars, and I was well on my way to learning far more than I ever would have thought about not only Supras, but cars and mechanical things in general.

Always, always, always be willing to step back and admit you don't know or don't understand something. Keeping humble might be the difference between a car that's still not cooperating and a car that's blown up due to overconfidence or simple ignorance. We're happy to help if you're happy to stay humble and learn to ask questions in a helpful manner. Some of the very best posts I've seen on here seeking help had the following:

-What the car is doing
-What conditions it was doing this under
-Driver inputs and car's outputs
-What the poster had done in regards to diagnosis
-What repairs / modifications have been made recently

Good input, good output. ;)


Yes, coolant in the combustion chamber has a steam cleaning effect on the piston as well. Consider how hot a combustion chamber is, coolant doesn't stand a chance! Pull those plugs, stick that bore scope in there (heck even a flashlight will do if the piston is near the top of its stroke), and take a look. If they're silver on top, ding ding ding... you found a BHG. Normal pistons will have a bit of carbon buildup, will looks brown to black, hopefully somewhat uniformly.

As for switching coolant, this is fine to do, however I'd caution you to REALLY REALLY REALLY flush it out. Different coolants have different chemical makeups, and don't always play well with one another. If I recall mixing green and red coolants can form a sludge of some sort, though the chemistry behind why I've forgotten. Either way, clogged cooling systems is a good way to cause an engine to run hot. I seem to recall running an engine with no thermostat, one end with a garden hose (or if you prefer, a lot of distilled water, like... a LOT, probably 10+ gallons at least), the other end open to flush out all the old coolant. Don't forget to have the heat on full blast and / or manually open the heater valve on the firewall to get all that coolant flushed out too.
Yes! I do know about the issue with coolant change. I planned on doing a complete flush with a hose first. Still trying to figure out whats up with those aftermarket parts, but that's not terribly important.
 

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Make sure you flush the heater core too. The green is ethyl based and the red is silicate based, together them make poo.
 

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Yeah, the Toyota Red is legendary, but I would personally not be chasing it. There's nothing wrong with aftermarket quality coolant and what's nice is you can have an issue on a road trip and find your coolant at any store. Where the Toyota stuff is dealer only and expensive and some of them are no longer stocking the concentrate but only the premix so they get to charge you for water. I should be advocating for the red, but literal decades have slowly turned me away. (Though last year I did flush and fill one of the cruisers back to Toyota Red in a burst of "keep it stock" passion....)
 

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Discussion Starter · #33 ·
Yeah, the Toyota Red is legendary, but I would personally not be chasing it. There's nothing wrong with aftermarket quality coolant and what's nice is you can have an issue on a road trip and find your coolant at any store. Where the Toyota stuff is dealer only and expensive and some of them are no longer stocking the concentrate but only the premix so they get to charge you for water. I should be advocating for the red, but literal decades have slowly turned me away. (Though last year I did flush and fill one of the cruisers back to Toyota Red in a burst of "keep it stock" passion....)
I have a dealership less than 3 miles from where I keep the supra, and last I checked they stocked concentrate. To be fair I dont know much about coolant other than OAT vs IAT. Im just used to topping off my 5.3 with dexcool every so often lol.
Just wondering here, how good is the stock intercooler and radiator on the 7ms? Is there anything I should upgrade if I plan on upping the power in the future?
 

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I have a dealership less than 3 miles from where I keep the supra, and last I checked they stocked concentrate. To be fair I dont know much about coolant other than OAT vs IAT. Im just used to topping off my 5.3 with dexcool every so often lol.
Just wondering here, how good is the stock intercooler and radiator on the 7ms? Is there anything I should upgrade if I plan on upping the power in the future?
I have made a habit of keeping a couple bottles of coolant handy, take one with us on road trips, just in case. Will have to check the MSDS on the Cat coolant, I was under the impression that it was the same as Toyota Red, but the question of silicates has me wondering now. It's supposedly good for 500k or something silly like that, but I like to know things like this.

Stock intercooler was good for stock power levels, for one or two pulls. No need to go with a ginormous setup, a 3" bar / plate setup from Driftmotion will do you well. I run a ginormous setup on my car, because I built it for road racing. It's honestly oversized, possibly to the slight detriment of throttle response, but intake temps stay pretty consistent. My Mustang friends used to freak out when they would see my IAT's around 140°, because theirs were only like 95°. What they failed to take into account was the fact that theirs was on the intake tube of an NA engine, meanwhile my sensor is in the manifold of a force induction engine... of course it's higher.

Stock radiators were actually a really nice unit, but at this point they're getting on in years. Does yours have metal end tanks? If they're plastic, it's most likely a parts store replacement. Oh, and this is what happens if you don't run enough coolant in a state where things get cold:
Automotive tire Art Wood Gas Sculpture


If you find yourself wanting a new radiator, I'd look to Koyo.
 
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