86.5 Toyota Supra Prollems

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I have a 1986.5 Toyota Supra which is having some cooling problems. First of all, I must put water in the extension tank before i drive it every day, and sometimes the radiator too. Now after I drive it for about 20 minutes or less, and open up the hood, after it is off of course, the water in the extension tank is boiling, and then after a minute or two, gets sucked back into the radiator. Then sometimes, the radiator spits too much water back into the tank and it overflows boiling water onto the ground. Also, when I don't add water before i drive it, then once i stop and turn it off, steam pours out from under the hood. Im not sure from where. Now i have heard that the problem may be the head gasket which is often faulty in the 7M-GE (the one i have) and the 7M-GTE. I have also heard that this may be a thermostat problem or a radiator problem. What are ya'lls opinions?

EDIT: I am pretty sure it is 86.5 model because the 86 and the 86.5 are different generations. The 86 is 2nd generation while the 86.5 is 3rd generation. They also look different. Also, the fan is working totally normal and fine, so it shouldn't be a problem with that.

posted by  Overtly Arcane

1986.5? so It's a 1986 model then lol, and would the extension tank be the expansion tank lol..anywayz, to put it bluntly it could be a number of things, fistly I'd check the fan is opperating correctly, I believe the Supra has a viscus fan which is should be spinning constantly although more so when it needs to ie; when the coolant temp rises enough, so, check the fan switch. If the fan isn't operating it will lead to the overheating of the engine which could in tern severley damage your head gasket and also the head it self which would probably need skimming due to the serverity of the case!

I hope this has helped ya!

And intro wouldn't go a miss either

posted by  Cliffy

Ok, so you are adding water to the cooling system each day? Either in the radiator and/or the coolant recovery aka. expansion tank right? Well, what you are doing is changing the boiling point of the fluid in the cooling system, hence this could be your "turn it off and coolant boils out of the recovery tank" culprit. See, antifreeze has a specific boiling point and so does water. You are adding more and more water everyday going towards a 100% solution of nothing but water by continuing to add it to the system. I am assuming you are not adding Antifreeze because you say WATER. Would I be correct? The reason why the cooling system fluid(whatever % mix you have now) in the expansion tank is boiling after driving it is due to one of a few reasons. Either your engine is overheating for some reason thus superheating the fluid......the fluid's boiling point has been lowered due to the excess water in solution, or you might have a blown head gasket and the boiling is actually not boiling, rather lost engine compression leaking into the cooling system and getting back into the tank. I don't have enough information from your posting to determine that. The radiator spitting back coolant/fluid into the tank is probably due to expansion, etc. My guess with your next comment of steam coming out from under the hood if you don't add water is due to fluid deprivision in the system, period. It's low on coolant and the steam is more than likely coming from the recovery tank as there is no where else for it to come from unless the system which is closed, had been opened by something bursting.

Now, with all the boiling over and pouring our and whatnot, it is hard to say how exactly you are losing coolant. I WILL say that in the absence of a leak or any loss of fluid due to a leak......if you are having to constantly add coolant/water.....you are more than likely looking at a blown head gasket. That is the only place for it to go, the combustion chamber to be burnt up. Are you seeing any excess WHITE smoke that smells like antifreeze coming out of the tailpipe? You mention nothing like that in your posting. Let me know. If that is the case, problem solved.

What to do: Here is what I would do with the information you've given. COMPLETELY drain / flush and refill the cooling system with nothing less than a 50/50 mix between antifreeze and water. (Many antifreezes are already 50% reduced on the market.) While there is NO coolant in the engine and you have it drained, make sure the thermostat is ok and working. Take it out and boil it in water on the stove. Once the water on the stove is boiling, we know it is 212 degrees F at sea level. The thermostat's temp. tolerance should be below that(IE...195), thus once you have the thermostat in boiling water, it should be opened up. If it does not work, replace it. Replace the gasket and reinstall thermostat as well as refill and evacuate all air from the cooling system. Once this is done, run the car and see what it does.

NOTE: Running mostly or close to 100% water in a cooling system is NOT good. Coolant, aka antifreeze is a fine mixture of lubricants for the cooling system components like the water pump as well as rust inhibitors for the internal passages of the engine. Always maintain a close to no less than 50/50 mix of coolant to water. Let me know what happens and good luck. That is the best I can do with the inforation supplied! :smoke:

posted by  cmeseadoin

Hi again, I just noticed your edit, a word of advice for future reference, if your post has been replied to simply put any further info in another post, this is because people only tend to read the opening post once, it was only by chance that I read it again :thumbs:

posted by  Cliffy

One further addendum that I thought of...to my posting earlier is that this boiling out when shut off COULD be caused by a stuck open thermostat. What would be happening in that case would be that the coolant would be in an open system within a closed cooling system (make sense?) and all the coolant from the top of the block or wherever the thermostat is located would be backflowing to the radiator and overfilling it, so still red hot, it is draining to the recov. tank and spilling out??? This "boiling" would be further magnified with the more water concentration in the coolant than actual "antifreeze."

See engines are designed to run up to over 200 degrees F and still maintain composure. When you shut an engine off, it actually gets hotter for a few minutes than cooler because the cooling system has now been shut down too because the water pump is no longer working. Water boils at 212 degrees F at sea level and we'll assume sea level for this discussion because anything else is negligable. If that coolant has become mostly water, CHA-CHING.....then you will boil out and over at 212 degrees F.

posted by  cmeseadoin

Well, I talked it over with my mechanic, who is a specialized Toyota mechanic, and he says that the 86.5 supra is the worst model ever made. It has more problems than any other supra. He says the main problem is definately a blown head gasket, possible tubing and hose deterioration, and a possible broken harmonic balancer cause by a timing belt being incorrectly replaced. The reason I was not running with antifreeze was because I tried that for a while too, with different ratios of AF to water, and it still boiled after I drove it around. After buying an awful lot of antifreeze, it became too expensive for my budget, and just started using water.

I also talked about repairs and their costs with my mechanic and i am having trouble believing his estimate. For replacing the head gasket and doing all the work associated with that, along with checking and possibly replacing the harmonic balancer and timing belt, and a lot of new hoses and tubes, a few other things included, it would total to about 2500-3000 dollars. Does this seem correct or am i being screwed?

posted by  Overtly Arcane

That does sound a little high to me but it is a Toyota Supra. A little on the high side for JUST the head gasket but he is doing some other work as well. Price it in several places and see how things compare. NOTE: you need to use antifreeze in a cooling system and not just water man. I see your point with the costs, LOL, but I am afraid that automotive design has made it such that antifreeze is the fluid of choice for cooling systems. I would not recommend that if engine oil is too expensive for you that you start using brake fluid. You will wear out the components of the cooling systems, possibly crack your block,etc. with water. Good luck!

posted by  cmeseadoin

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