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PSA do not use a non oem or racing application thermostat in a 4g63

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Murdertalon

Proven Member
396
82
Jul 7, 2016
East side, Washington
PSA do not use a non oem or racing application thermostat in a 4g63

As the title States steer clear of your local (parts store) for a thermostat if you care about your engine.

I thought replacing my thermostat with a new one from a local parts store was a good idea at the time (gasket was bad) it was leaking a little what I didn't realize is that the brand new thermostat I got from autozone never actually opened. This would lead to overheating, fans not working, CEL code throwing for insufficient operating temp.

Take my advice it's been said before, but if you care about your engine get the thermostat from mitsubishi or a reputable racing parts company (mishimoto comes to mind)

The part number for evo7 and evo9 looks to be the same as the DSM 2g (pay attention to temp operation) looking at the evo9 one oem opens at 176f and full open by 199f those are pretty good numbers.

If people have specs and real world experience with some different thermostats I'd like to know how it looks on temps.

230f is too hot for our DD dsm's they like to run about 180 however I have found if your thermostat starts opening at 180 it's not going to keep it real close to 180 it will run hotter.
 
I've went to a 170 thermostat. Didn't notice much of a difference really. The downside to running a cooler thermostat is that your car might take a long time to warm up and it will affect the o2 going into closed loop. But I do agree these cars run a little hot for a daily driver. Especially with a FMIC and AC in the way.
 
It's possible to get new parts that are bad. I've had an Autozone thermostat in my Talon since I put it together 10 years ago with no issues. With as many cars as I've worked on, I've gotten bad parts from dealers and parts stores alike. It's just one of those things that happens. This is why I choose to run gauges I can monitor.
 
If your fans aren't working, I'd say that's a big part of the problem. They should turn on when you reach a certain temp, regardless of what the thermostat is doing.

I run cheap auto parts store thermostats and have in every car I've owned. A $3 part with a lifetime warranty beats out a ~$30 part that does the same thing.
 
If your fans aren't working, I'd say that's a big part of the problem. They should turn on when you reach a certain temp, regardless of what the thermostat is doing. I run cheap auto parts store thermostats and have in every car I've owned. A $3 part with a lifetime warranty beats out a ~$30 part that does the same thing.

Actually I think there is a sensor that tells the fan to engage but the water in the radiator has to be 210* in order for it to engage. I am not sure what sensor turns on the fans but I can tell you that at 230*f looking inside my ECU it was not turning the fans on. This leads me to believe there is another sensor somewhere in the loop that activates the fans. After I permanently opened the autozone thermostat that is in there currently the fan turns on exactly at 210* and shuts off about 199. Keep in mind 5 minutes before while that thermostat was not opening the engine temp was 230* and not flowing coolant it was not turning on the fans by its self.
 
2g fans are controlled by the ECU based on ECT. 1gs have a seperate fan switch in the radiator, but the 2g uses the same sensor (ECT sensor, the bigger 2 pin plastic plug one) it uses for the ECU.
 
You can disagree if you want, but that's how it works. Where and how did you measure the 230*? If it was the ECU saying 230 and your fans are setup in stock form the fan definitely should've been on. 2g ECU controls the fans based on A/C, ECT, and VSS.
Here is the various fan operation parameters from the FSM. Ignore the handwriting don't know what that's about.
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Yes logging via OBD2 port in torque. I cant explain it, I know the ECU controls the fans but without flow through the thermostat they don't turn on. It was driving me insane. Is it possible that I have a fan temp switch somewhere in the radiator? IDK man I should have taken videos of it. Maybe I will play with it when I get my evo9 thermostat in the mail.

The only fan that came on after I pulled the thermostat is the passenger side one or the right one. It did come on though at idle 0mph and 210* but only after I pried open that autozone thermostat to fail safe lock. 5minutes before I was driving on the freeway at 219* and no fan would auto turn on.

I just replaced both the 2prong temp sensor (main) and the single pin one. Is there another one on the engine or head or radiator somewhere?
 
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The 2 pin is the ECT and the single pin is the sender for the gauge. Those are the only two coolant temp sensors. If I'm not mistaken on a 7 bolt they're both below the thermostat.

Perhaps something is wrong with your fans. How do you know they didn't come on when you were on the freeway? They won't do much for cooling at highway speeds. And pretty much nothing for cooling if the thermostat is stuck shut, as there's no flow through the radiator.
 
The 2 pin is the ECT and the single pin is the sender for the gauge. Those are the only two coolant temp sensors. If I'm not mistaken on a 7 bolt they're both below the thermostat.

Perhaps something is wrong with your fans. How do you know they didn't come on when you were on the freeway? They won't do much for cooling at highway speeds. And pretty much nothing for cooling if the thermostat is stuck shut, as there's no flow through the radiator.

I stopped the car at a gas station because I was manually turning on both fans, I turned on the AC switch for the passenger side one and run a jumper wire for the drivers side one, and had my heat on full blast and my cruising temp was 219* I stopped and the car idling I tested to see if the fans would come on on their own and my car hit 230* and the lower radiator hose was cold.

This caused me to start panicking more I let it cool off a little then ripped the thermostat out and used a pair of pliers to bend it and force it to hit the fail safe locks and be permanently open. much to my surprise as soon as I did this and my car hit 210* idling but now with an open thermostat and my fan comes on and off like clock work.
 
After going external wastgate on my car i had to go to a colder thermostat . I installed a stant and the only thing i noticed is that in really cold weather it takes longer to reach operating temp but it did fix my high temp in the summer . I run the stock main fan wired to come on high , a larger radiator and a pusher fan for my a/c mounted in front of my radiator to make room for my external recirculated wastegate .
 
I just replaced both the 2prong temp sensor (main) and the single pin one. Is there another one on the engine or head or radiator somewhere?

Just a theory, but you may want to check your temp sensor to make sure you have the right one. It's tricky for '95s because they used different CTS sensors for the Eclipse and Talon, and the CTS will fit either harness. To check it, put a multimeter to it. At room tempature, if you get around 2000ohm you have the right one for a Talon, if it reads ~10000ohm that's for the Eclipse.

Your problems sound exactly like what was going on with my buddy's '95 Talon. Swapped the CTS and that fixed it.
 
Another good option for wiring up slim fans is to wire them through an aftermarket relay/sensor. Here is an example of what I mean:

https://www.summitracing.com/parts/rfw-ar78/overview/

There are different configurations for different needs and you can select different temp ranges to fit you needs. I like this one as it turns on at 200 and will turn off again at 185. For me, this is where I like my car to be. There are colder sensors too. I don't like to adjust coolant offset as it will pull timing sooner with the offset. If you happen to run a 1G radiator in your 2g, you will have an extra coolant bung next to the lower radiator hose to use for something like this.
 
Just a theory, but you may want to check your temp sensor to make sure you have the right one. It's tricky for '95s because they used different CTS sensors for the Eclipse and Talon, and the CTS will fit either harness. To check it, put a multimeter to it. At room tempature, if you get around 2000ohm you have the right one for a Talon, if it reads ~10000ohm that's for the Eclipse.

Your problems sound exactly like what was going on with my buddy's '95 Talon. Swapped the CTS and that fixed it.

Is this really true? Seems to be quite odd. I have found that most aftermarket sensors are simply all over the place.
 
^ no that's not true in the slightest. +1 on the Painless thermo switches they work great, mine operates within 3* of the rating.

That's what i thought. Was just trying to not be a ****.

+1 on checking with a ohmmeter
 
^ no that's not true in the slightest. +1 on the Painless thermo switches they work great, mine operates within 3* of the rating.

Really? http://www.dsmtuners.com/threads/resolved-2g-coolant-temp-sensor-question.328009/

That's the thread we found when we were troubleshooting that same CEL with the fans not turning on. Looks like the OP found the same thread because he posted in it earlier this week, so I'm assuming he has the right CTS now. Also looks like the difference might be turbo vs non-turbo as opposed to a Talon vs Eclipse thing. Either way, it's a pain to find the right CTS for a 95 DSM from a local parts store.
 
All 95-99 turbo eclipses and talons use the same ECT sensor. The problem in a few threads here is advance or AutoZone whatever has the wrong part number in their system.
There is no difference in a turbo eclipse or talon other than badges/logos and ground effects.
 
PSA do not use a non oem or racing application thermostat in a 4g63

As the title States steer clear of your local (parts store) for a thermostat if you care about your engine.
I've had a Stant 14077 (170*f) in my daily-driven GST for a few years and it works absolutely flawlessly. The gauge rises to somewhere just below half and stays there rock-steady no matter how hot or cold it is outside.

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I had a bit of an overheating issue initially which led me to believe the OEM thermostat may have been faulty...with 15 years and 145K on the car at the time I figured I had nothing to lose by replacing it, but in reality the overheating issue turned out to be a bad radiator that wasn't doing it's job. I replaced the rad with a new aftermarket model and never had an issue since.
 
Glad to hear those thermostats are doing you well. I got one of a slightly different design and it was (fail safe) but it didn't open at all let alone enough to hit the fail safe lock tabs. Doing some research Cosworth makes a thermostat for the 4g63 that is supposed to hold more of a constant temp once hot rather than keep opening and closing.. I found someone that ended up using a GATES 33987 thermostat for a different application that worked better for temps than the Mitsubishi recommended one.

http://www.dsmtuners.com/threads/thermostats-reviewed.482406/

My radiator is fine, fans are fine once I opened that thermostat with a pair of pliers. My temps went so low on the freeway I had to grab a piece of cardboard and block off half the rad to run at 170* @ 70mph. I would say that's pretty amazing because I thought for so long my radiator was bad/old/corroded.

With the correct temp sensor it showed me that the thermostat had an issue, then once I figured that out my temps are low low now if I need them to be. I ordered an evo9 thermostat because it shows the same seal part number as the factory 2g so I figure its the same size. Ill let you know if it works well or not when I get it. Just checked should be the same 56mm.

Sometimes I get carried away with the detail that I add in here to these posts, I just hope my trouble shooting saves someone else some headaches. I want to see more DSM's on the road and less in the garage in parts :dsm::laser: :thumb:

I have a feeling that I'm not the only one that has unknown drove around for weeks with a thermostat that wasn't opening, I just got lucky on this head gasket that it was winter and I always had my heater on blast.
 
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