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Overheating
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Let's list some reasons your car might be overheating and include the reasons and likelihood of each cause. Remember too that it can be more than one cause or contributing factor. Think of the system as a whole not just each part.
I'm only going to address stock systems mostly because once you start doing things like putting a large intercooler in front of your radiator and other such stuff like bigger radiators and other issues then things will change. Not saying that many of the things listed below won't still apply but only that it's getting a bit outside the scope of this basic informational webpage. Same with a leaking headgasket and troubleshooting things similar to that which are major engine problems and not just simple overheating. That goes beyond this page. But this is a good place for your to start, especially if all other things considered your car is running fine, not smoking or have junk (like oil) in your coolant and so forth.
Note that some have thought their car was overheating when in fact it was not. The V6 engines in your 3000GT can run hot. 200-210F isn't something to get worried about. Of course without an aftermarket gauge you won't know the exact temp so let's say that when you get above 3/4 mark that is now starting to get to the area of overheating. If you do the basics mentioned here and are still concerned then you will need to get some actual temp readings from installing an aftermarket gauge.
And yes, you can over-cool the engine by doing things like rewiring your fans to stay on all the time and other such foolish "mods". So don't do things like that because your just asking for problems.
Leaks
should be taken care of first thing. Especially any leak that leaves a puddle.To make sure you will want to pressure test your coolant system and them visually inspect for leaks.
Age Of The Coolant
can certainly be a factor. I've seen too many 3Ss that were not taken care of and that ALWAYS includes the cooling system. The conventional antifreeze (remember this from page 1?) needs to be changed every 2-3 years or every 30,000 miles. The problem is: IT DOESN'T GET DONE!! You've got previous owners that went 10 years and 100,000 or more on the same old coolant. No kidding! The antifreeze protection has long ago expired and the cooling jackets and other passages are gunked up (technical term, lol) or have a nice film of CRAP (another technical term) that prevents efficient transference of heat. Even with new coolant dumped in there it cannot work well past all the corrosion that is in the block and passages!
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In short, the car was not properly maintenanced and the cooling system has been damaged. Very simple. So what needs to be done is a serious clean out of the entire cooling system. More than just a distilled vinegar run and rinse. An entire chemical flush is the best you can achieve with the engine in the car. I won't get into this procedure or specifics (plenty info out there) but if you don't know the history of your car and/or suspect a previous owner did not maintain the car well (at least the cooling system anyway) then THIS IS INDICATED as a source of your overheating problems. While it might not be the sole cause of your overheating concerns it will be a contributor. |
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In short, you should pay attention to your coolant system just as you would your oil system or other important service/maintenance on your car. You have to change your coolant at regular intervals or your engine will suffer. You can also easily check your coolant with simple test strips if you like (see example to the left). The example shown will give you the boiling point, freezing point, pH levels thereby detecting the acid levels that can do damage. STB used by many US Military motorpools. Anyway, very inexpensive way to keep tabs on your coolant if you prefer. |
| What Coolant Mix you are using will have a direct affect on the ability to cool. The more % of water the better cooling you will achieve. But you still need those three other properties of the antifreeze as previously discussed. Just remember that you can drop the % of antifreeze and improve your cooling ability. Same with adding the Redline WaterWetter additive to assist in the efficiency. Definitely NEVER use over 50% antifreeze. |
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Shroud & Ducting Panels
are extremely important to the directing of air. That air flow is what is removing your heat from your engine via the radiator! If your radiator shroud is not in place then the air is easily directed around your radiator instead of through it. Air, like other mediums, will take the path of least resistance. So if you are missing your radiator shroud from a lazy previous owner or some other odd reason then get it back on there. If you lost it, order a new one. If you changed front bumpers then you need the matching shroud if your previous one doesn't fit. You need to have the air coming in from the front being routed through your radiator. The same goes for the lower "splash shields", aka - the front active aero spoiler. This is also important in the flow of air. Not as much as the radiator shroud piece but it contributes to the flow. This is usually always in the top reasons for a 3S overheating!
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Damaged Radiator Also note that the VR4 has a larger radiator than the non-turbo 3000GT models. Something for you to know. |
| Thermostat is another common part that gets blamed and it can be a likely candidate for repair. I would recommend only replacing with an OEM from the mitsubishi dealer (or other supplier of 3000GT parts) rather than the corner auto parts store. And make sure and install with the little jiggle valve pointing UP. A faulty thermostat can certainly cause problems. Stuck open all the way just means forever to get to operating temp but stuck partially or closed and you have a problem. You can usually get a feeling for it when you are at operating temp and can feel the upper/lower hose temps on the jacket (a quick check but not a positive indicator if partially stuck). And if the first part of this section is true (your coolant was/is old and not maintained well) then this would also affect the thermostat by introducing corrosion and possible damage to the metal. The same would be true of a system that had leaks and wasn't kept full (air) as this will greatly increase potential damage to the thermostat. Remember, it's a "moving part" in your cooling system. |
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Radiator Cap remember your VR4 system is a closed one and under pressure. Your cap must operate properly by release pressure when it should as well as keeping the system pressurized to the right psi. Some say you can also add a higher pressurized cap but for a stock system I wouldn't recommend that as a fix to a car that has a problem. Yes it will improve boilover protection but on a stock vehicle there's another reason to look at rather than try such a bandaid style of repair. It can also cause leaks from the higher pressure. Just make sure you have a good condition cap and the stock setting. It's not like they are expensive and they do wear out / go bad. |
Fans
Many times one or both of the fans fails to come on and you will overheat. Check that your fans are operating correctly. If you are overheating then they should both be on high. The passenger side has two speeds and the drivers side has one speed. There are several ways to check the fan operations on the different years (1G and 2G) as well as both fan functions. I won't elaborate here as that is again beyond the reason for this page and also is covered in the Mitsubishi FSM (Factory Service Manual) and if you are getting that in depth you really need to have the FSM on hand. But here is some info that may be of help:
Radiator fan on at low speed - above 95ºC (203ºF)
Both fans on at high speed - above 105ºC (221ºF)
Both fans off - below 95º (203ºF)
Drivers side fan also goes to high whenever AC is turned on.
Fans turn off above 50 mph
Radiator Fan means the passenger side fan. The AC Fan is the drivers side fan.
Note that the fans shut off when you go over 50mph. That is because you will get better airflow at anything higher than that speed with the fan off. One more reason to not do foolish things like rewire your fans to stay on all the time. Also note that the OEM mitsubishi fans are top quality and you won't get better performance from others out there. The only reason some people change fans setups is due to reduced room from bigger radiator and/or larger turbos.
Water Pump
This has been the cause of some cooling system problems but it is not very common. And usually it isn't a problem for long because it will fail or seize and you will know it fairly soon. So don't jump to this conclusion as it is much more likely to be something else. Of course if your pump is leaking (it has a little path/hole that will tell you that) then you need to arrange to change it asap. If it seizes then you may end up with a severely damaged engine because it will cause the timing belt to break (from the heat of friction against the seized pump).
Well, those are the basics. There's really no other basics that would cause your 3000GT to overheat. If you properly covered the items above then your car should be running at the temperature it was designed to and under the conditions it was meant to. If you have any questions, feedback or anything else let me know!