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Overheating issue has me stumped

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90-GST

10+ Year Contributor
106
1
Aug 15, 2008
St. Louis, Missouri
I have tried just about everything and still can't figure this out. I have a 97 gsx that I rebuilt. It was sitting for a year and a half with the engine just sitting in by motor mounts, and just recently did I get it running again. And I've had this problem the entire time.

At idle, it will be fine. It will run around 180-190* for 20 minutes. But when I start to drive it around it starts to get hot. I have replaced the thermostat with a 175*, flushed the system, replaced the radiator with a brand new cx racing aluminum one and two slim fans(which are always on via link), replaced the radiator cap, made foam ducting between the radiator and fmic, used two bottles of water wetter and a 40/60 coolant/water mixtere.

When I drive it, the temp slowly creaps up. Around town it will run 186-193ish except for hills, it will get to 210 sometimes, but when I get on the highway, or exceed 50mph, it will increase. 200 to 203, back down to 200 for 5 seconds, then up to 203 again. And continues to do this from 203 to 206, 210, 213, etc. It seems like once it gets to a certain temp, it just gets worse. Almost like it looses water, because after it overheats, I've got to add a decent amount. When I get off the highway, it will run 223-229 unless sitting it will go up.

This problem is getting extremely bothersome. I'm trying to sell the car, and I can't very well do that with it overheating. Any ideas?





I thought it might be beneficial to know that I took the front bumper off, and it would run 206-219* on the highway, but never really got hotter than that. But when I put the bumper on it will get hotter. Even after the ducting.
 
Make sure the fans are blowing in the correct direction. Take a piece of paper and make sure if you have them pulling they're pulling, or if you have them pushing there pushing. Also if you have to keep adding coolant after trips, you either have a coolant leak issue (test with a pressure tester) or your head gasket is on its way out.
 
I am having a similiar problem. Have done all of what you mentioned along with new t-stat and vented hood. At this point there really are only two things left, the water pump or the head gasket.
I'm pretty sure it's a head gasket issue for me. I don't believe the finish was good enough on the head surface for the Felpro PermaTorque MLS gasket I put on and although it's not enough of a bad seal that I loose any coolant, I believe it is allowing exhaust gasses into the coolant and heating it up.

So far I can control it using my heater when needed so I'm dealing with it until I get my other DD car back working. Once that is done I'll pull the head and put a composite gasket on. I don't run more than 22psi anyway which a composite combined with ARP studs can handle all day, no problem. I feel stupid for even wasting my money on this $200 head gasket. While I'm there I'll replace the water pump with an OEM as well. I'm pretty confident that my overheating issues will be resolved after doing these two things.
 
Check the water pump, Also get the shroud setup with the slim fans.
How should I check the water pump? Apart from pulling it off. It isn't leaking any fluid out.
Make sure the fans are blowing in the correct direction. Take a piece of paper and make sure if you have them pulling they're pulling, or if you have them pushing there pushing. Also if you have to keep adding coolant after trips, you either have a coolant leak issue (test with a pressure tester) or your head gasket is on its way out.

The fans are set up as pullers. They will hold paper to the FMIC after the ducting work I made; although it is very weak at the fmic.

And I changed the oil, it was rather dark for the 250 mile change, but had no green tint, or milkiness to it.
 
Check the water pump, Also get the shroud setup with the slim fans.

I also suffered with this issue for a long time, until I did the shroud install. I had worries that it would not clear my turbo but, it fit perfect. Now my temps are between 186-196 and will not get hotter than 196.
http://www.mishimoto.com/mishimoto-aluminum-fan-shroud-kit-mitsubishi-eclipse-90.html
 
The fans being on 100% of the time, if they are not a high enough CFM, can cause an airflow blockage to the radiator while driving at highway speeds. Let the fans get controlled normally and see what happens.
 
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A simple way to test the water pump is to leave the radiator cap off, start the car and see how much and how fast the coolant is being pushed through the upper radiator house. If it seems slow or not a lot of coolant then your pump could be going bad, or it could mean you have a clogged radiator but you said in your first post you just replaced that so it's probably not the case here. Also alot of people say having both fans as pullers is the best for dispersing heat, but I personally have one pusher and one puller fan on my setup with no ducting and a 160 deg thermostat and I can maintain 158-165 engine temps while cruising and at WOT.
 
A simple way to test the water pump is to leave the radiator cap off, start the car and see how much and how fast the coolant is being pushed through the upper radiator house. If it seems slow or not a lot of coolant then your pump could be going bad, or it could mean you have a clogged radiator but you said in your first post you just replaced that so it's probably not the case here.

That just seems like a way to tell if it is maybe the water pump. I'm not trying to just keep throwing parts at it hoping it fixes it. I'm trying to locate what is causing the problem, and fix that. But it seems like there isn't really a way to do that. I'll try this since I have no other options. I just need to get this figured out asap.
 
Two words = STOCK FANS

Six more =- Slim fans Suck For Daily dirvers

se4riousely not trying to be rude at all, was meant for a laugh, but i went through hell and back with overheating and tried EVERYTHING and what finally fixed it was going back to a bone stock radiator, with both bone stock fans. no super slim line or anything worked, no water wetters, NOTHING..simply put the stock fans are designed to flow a LOT of CFM and pull from the entire face of the radiator,, slim lines pull from two little circles and because of the way they are made there's about a 6" center of that circle that gets no flow just like all the areas that aren't covered..it's like putting in a half radiator.. I rebuilt my entire FMIC piping and welded a 90* elbow on my compressor housing in order to fit that setup back in but now i'm back to running my AC in 100*F + weather and never seeing coolant temps above 205 nless i forget to turn the fans on at a light (on toggle switch and i turn thgem off on the highway to save them some work)

I've responded with this same thing in at least a dozen other threads just like this and in most cases i got a PM later on thanking me for convincing them to go back to stock fans

another big thing butmainly at idle is an OEM water pump, expensive = yes, worth it? = yes parts store remanufactured ones often have inferior impeller fins that barely move water untill you're up in cruising RPM's and cause issues at idle and in traffic..

hell back on slim fans and an ebay CXracing AL raditor, I couodn't even drive on the highway with the AC on if the weather was over 75* even with fans on... there's no replacement for the amount of air the stock fans can flow on speed "3" (they have hi, lo and then both hi and lo running together for three speeds, i have mine to always come on speed three)

I also have moreroom with a stock radiator now too for my wastegate dump and down pipe, the aluminum ones push everything way out with those big fan mounting stubs on them when using stock fans like they are setup for , but if i was able to run a PTE6776RS turbo and large greddy FMIC fora supra with stock fans and radiator you should be able to as well with anything smaller than a GT40/42 framed turbo
 
A simple way to test the water pump is to leave the radiator cap off, start the car and see how much and how fast the coolant is being pushed through the upper radiator house. If it seems slow or not a lot of coolant then your pump could be going bad, or it could mean you have a clogged radiator but you said in your first post you just replaced that so it's probably not the case here. Also alot of people say having both fans as pullers is the best for dispersing heat, but I personally have one pusher and one puller fan on my setup with no ducting and a 160 deg thermostat and I can maintain 158-165 engine temps while cruising and at WOT.
I think your a little to cool, the engine should at least hit 180*. You might be running piggly wiggly rich....:confused:
 
I ran the car with the radiator cap off and the flow seemed pretty weak, but I'm not really sure how hard it is actually supposed to be. I tried to pressure test the cooling system but the tester I rented didn't fit the cap.

Two words = STOCK FANS

I can't run both stock fans. I can only fit the passenger fan because of my external wastegate. Right now it sits about 1/2" from the slim fan. I figured that 2 slim fans would work better than one stock fan.

another big thing butmainly at idle is an OEM water pump, expensive = yes, worth it? = yes parts store remanufactured ones often have inferior impeller fins that barely move water untill you're up in cruising RPM's and cause issues at idle and in traffic..

And the other issue. I don't have a problem at idle. But once I get on the highway I will start to have a problem. It runs fine, for the most part, around town at speeds of up to 40 mph.
 
You need the black magic brand fans and have a sheet metal shop make a custom shroud to make the fans pull air from every inch of the radiator, that's the only7 other way i've seen a DD built 2 stay cool even with AC
 
I ran with one stock main fan with an aluminium rad daily with consistent 195-200 temps with the holset i only have enough room to run the ac fan in place
Of the main, i hope it works, but extremepsi is sending me a new 12 inch fan with mounting brackets
 
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