running hot (not quite overheating)

1998 MITSUBISHI ECLIPSE
89,000 MILES • 2WD • MANUAL
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BOOSTINFLGST
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I've been chasing an overheating problem forever now. The car is actually not overheating but continually runs hotter than its supposed to. I have a '98 Mistu GST Turbo with 89k. I've replaced pretty much everything in the coolant system at least once. New radiator, water pump(w/20k on it now) 2 oem thermostats and oem rad cap, and both temp sensors(gauge and ecu) and confirmed fan comes on once operating temp has been reached. The needle normally runs right in the middle of gauge and now runs 2/3 to 3/4 up gauge. I pulled the first oem thermostat and drilled 2 small holes, which helped and it only ran slightly hotter than normal. Then i purchased a new 2nd oem thermostat and it runs hot again about 3/4 way up gauge. Also, once it does start running hot i can push in clutch and coast and temp immediately drops to middle of gauge and then if i put back in gear it jumps right back to where it was. If i leave it out of gear and coast, it will drop down but slowing climb back up to 3/4 of gauge.


Forgot to mention. First oem thermostat that I mentioned was new as well and had same effect and 2nd oem thermostat, before removing and drilling the 2 small holes. Those this has worked the best I pulled it so I can try to fix the correct way instead of the band aid fix. I also purchased a coolant pressure tester kit and found the system does hold pressure, although I have not tried this once the car has reached operating temp, not sure if that will make any difference.

I've been meticulous about getting all air out of the system. With the oem (non drilled) thermostat it will overheat during any condition once driven. If I start it and just let sit it will reach operating temp and maintain. Once driven, street or highway it goes to 3/4 on gauge. With the drilled thermostat it runs fine on the street(wouldn't even know there was a problem) and on highway it usually ready slightly higher on gauge about, 2/3 sweep.

Well the wate rpump is run off the timing belt, both of which were replaced about 20k ago. I have a program on my laptop and cable that I can hook up to the obd2 port and will read was temp the ecu can see, because it uses a diff sensor than the one for the gauge or rule that out. Otherwise, if it possibly a head gasket, can/should I do the pressure test after its heated up to possibly reveal a loss of pressure?

Please help!!
Feb 21, 2011 at 1:49 PM
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ERNEST CLARK
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First check that you don't have air in your system. Turn heat on high, run engine from cold to operating temp with rad cap off. (keep it at idle) Watch for air bubbles.

Also, when traveling at speeds on expressway, will it overheat then? You may want to check for a blown head gasket.
Feb 21, 2011 at 2:03 PM
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ERNEST CLARK
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Also, there's more than one way a head gasket can blow. The first way you've already eliminated by pressure testing the cooling system. That's when the coolant gets into the oil.

The other way is when the engine reaches temp, the metal from the block and head will separate slightly and on the power stroke, the cylinder will push exhaust gas into the cooling system. I've seen situations when a car is still drivable but only under highway speeds. And usually when you shut down the engine coolant will leak back into the cylinder. When you next start the engine you'd see white smoke out the tail pipe for the first few minutes as the engine burns it off.

Feb 21, 2011 at 2:14 PM
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BOOSTINFLGST
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Well the waterpump is run off the timing belt, both of which were replaced about 20k ago. I have a program on my laptop and cable that i can hook up to the obd2 port and will read was temp the ecu can see, because it uses a diff sensor than the one for the gauge or rule that out. Otherwise, if it possibly a headgasket, can/should i do the pressure test after its heated up to possibly reveal a loss of pressure?
Feb 21, 2011 at 3:10 PM
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MIGHTYMIDGET09
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Member did u finally figure out the main problem cause mine is doing thesame thing
Mar 19, 2016 at 5:33 AM
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STRAILER
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Hello,

This sounds like a classic blown head gasket. Here is a guide that will show you how to test to confirm the problem.

https://www.2carpros.com/articles/head-gasket-blown-test

Also, there's more than one way a head gasket can blow. The first way you've already eliminated by pressure testing the cooling system. That's when the coolant gets into the oil.

The other way is when the engine reaches temp, the metal from the block and head will separate slightly and on the power stroke, the cylinder will push exhaust gas into the cooling system. I've seen situations when a car is still drivable but only under highway speeds. And usually when you shut down the engine coolant will leak back into the cylinder.

When you next start the engine you'd see white smoke out the tail pipe for the first few minutes as the engine burns it off.As for the temp sensor, if the sensor is faulty, your scan of the computer will still read that faulty temp. But if the engine temp is different than the gauge reading, then the temp sensor for the gauge or the gauge is faulty.

As for the water pump, it's ran off the drive belt, not the timing belt. Big difference. And do not attempt a pressure test when the engine is hot! U can purchase an exhaust gas leak detector to test for the presence of gas in the coolant.
Jun 21, 2017 at 7:40 PM
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DAISYBEAR
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Engine Cooling problem
1998 Mitsubishi Eclipse 4 cyl Front Wheel Drive Manual 92000 miles
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My car just recently started showing a hot temp. It does not go into the "danger zone" on the temp guage and it fluctuates while I am driving and sitting in traffic. It hovers between normal and about halfway to the "danger zone". Sometimes it will go up or down when I am driving....sometimes it will go up or down when I am sitting in traffic. There doesn't seem to do one thing or the other consistently. I checked the coolant and it is full, however when I opened the hood after shutting the car off, I heard a "bubbling" sound....like boiling water. Any ideas?
Jun 21, 2017 at 7:42 PM (Merged)
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CHEINLEIN
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I would check your thermostat, or your water pump maybe you might check your heater core.. good luck
Jun 21, 2017 at 7:42 PM (Merged)
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MECHANICAL DUMMY
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Hello Carpros,

Ill keep this short and sweet. I have a 98 Mitsubishi Eclipse, 279,000 miles. For a while the car thermostat will go immediately straight up to "H" if it goes a long distance. For instance, I cant go to the grocery store ad back without puttig water in it. I have changed the thermostat 2 times. I discovered that 1 fan that is for the AC is not working. When I put water in the radiator the water will gently go down up kind of patter until the water goes down. I have puchased numerous Radiator cap and I still see whater coming from underneath it. I dont wat my sister to trade in her car for a simple problem if it can be fixed. Also, what is the differnce betwee a crack head and a blow head gasket. If its a crack head gasket do you reccomend the cheap stuff to fix it? I dont know...lol Please Respond

Best Regards,
Mechanical Dummy
Jun 21, 2017 at 7:42 PM (Merged)
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ASEMASTER6371
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you need a shop to insert a dye and find the source of the leak. you may have done more damage by driving it overheated and yes, it may have a blown head gasket and/or cracked head.
if the head is cracked, it add about 500-800 to the repair. if it is just the gasket, you may get away with about 1500. remember, the head gasket is a result of the leak, not the original issue. you still need to find out why it overheated to begin with.

Roy
Jun 21, 2017 at 7:42 PM (Merged)
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SABRINAJANDER
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i replaced the radiator took thermostat out and the car is still shooting all the hot water over to the over flow tank then it runs hot the water is boiling and it over flows out of the over flow tank. there is no sign of water in the oil and no smoke so i don't think its the engine.
Jun 21, 2017 at 7:42 PM (Merged)
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MHPAUTOS
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If the radiator is new and the thermostat is out, i would still be looking at a head problem, not all cases of head gasket failure do you get coolant in the oil as a first sign, go get a head check done, this is a quick and simple chemical test to check for exhaust gases in the cooling system, start here.
Jun 21, 2017 at 7:42 PM (Merged)
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SABRINAJANDER
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THANX I WILL DO THAT...
Jun 21, 2017 at 7:42 PM (Merged)
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JACOBANDNICKOLAS
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If you want, try this. With the engine cold, remove the radiator cap and start the engine. If coolant shoots out, mhpautos is exactly right, head gasket. The compressed air from the combustion chamber gets into the cooling system and coolant blows out. My method is a quick / cheap way to check. However, his way is more thorough.
Jun 21, 2017 at 7:42 PM (Merged)
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JJADKINS2112
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Engine Cooling problem
1999 Mitsubishi Eclipse 4 cyl Front Wheel Drive Automatic 130786 miles

i changed thermostat, fans are wired to stay on constantly, flushed radiator, and water pump is not leaking.. it begins to run hot after driven for awhile and today i noticed alot of water coming out of exhaust pipe and it smells like anti freeze.
Jun 21, 2017 at 7:42 PM (Merged)
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AJPTOWN503
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Engine Cooling problem
1996 Mitsubishi Eclipse 4 cyl Two Wheel Drive Manual 145000 miles

My car runs really hot after only 5 or 10 min idleing.iv replaced the thermostat and tested it before I put it in,its a new radiator and the cooling sytem was drained and properly bled.the tempature gauge reads in the middle and I'm guessin it works cuz it takes a minute to go from cool to the middle...there's no coolant in my oil or any signs of head gasket failure so I'm stuck....after the 10 min of running the hoses and cap ar so hot you can't even touch them but my friend who's good with cars suggested maybe my car is supposed to run this hot and that's just the way it was made but I'm not sure...any ideas would help and its a 4cyl 2.0 non turbo if that helps...thanks to whoever can think of anything
Jun 21, 2017 at 7:42 PM (Merged)
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MHPAUTOS
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Hi there,

Have you checked that the pressure cap is holding the correct pressure, as if the cap is defective you will have over heating issues, look here.

Mark (mhpautos)
Jun 21, 2017 at 7:43 PM (Merged)
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AJPTOWN503
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Yes I replaced the cap...I forgot to put that in the original message
Jun 21, 2017 at 7:43 PM (Merged)
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MHPAUTOS
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Hi there,

Just re reading your post again, with the engine at normal operation temp, you will not be able to touch the cap or top hose as they will be extremely hot, if the gauge is in the normal range, i would be thinking with all you have done that this is going to be normal,
i do feel that there is nothing to worry about here, a thermal scan of the radiator will give you a better feel for what is going on.

mark (mhpautos)
Jun 21, 2017 at 7:43 PM (Merged)
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AJPTOWN503
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Ok thanks...Iv just never had or seen a car that gets this hot this quick but I was pretty sure with what I did and everything else it was normal
Jun 21, 2017 at 7:43 PM (Merged)
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BCGURL2004
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my car has been running hot. i bought a cooling sensor but when it is plugged up the fans won't work but when you unplug it the fans come on,
Jun 21, 2017 at 7:43 PM (Merged)
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MHPAUTOS
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With the sensor out of the system, the fans will turn on, do you mean that the fans will not come on with the engine at high temp? have you changed the thermostat as yet?

Mark (mhpautos)
Jun 21, 2017 at 7:43 PM (Merged)
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BCGURL2004
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no they dont come on which is causing it to run hot and i have bought a thermostat, radiator cap, we took the radiator out and it looks fine. i went out to crank it this morning and at first it wouldnt crank and the it crank and cut back off, and about 5 mins later i went to crank it and it crank right up.
Jun 21, 2017 at 7:43 PM (Merged)