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2001 Spyder GT
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Discussion Starter · #41 ·
I did what you guys have said. Filled the rad (just water) to the top of the neck and the overflow to the cold mark. The gauge shows it gets to the three-quarter mark and then drops to just below half. Then, when I stop, it pukes out onto the road. Has done this repeatedly ... I have no clue why this is happening. When I changed out the intake, that got rid of my fast idle and the car runs really well other than spilling out the coolant.
 

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2001 Spyder GT. Koni adjustable shocks. cold air intake, ST sway bar.17X8.5 rims. LED headlights.
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Can I put a THEORY out there ? [Don't beat me up if it does not work]. You just said you are using plain water instead of coolant. Water has a boiling point of 212°f. as we all know. Above that it turns to steam. Steam has a spacial volume of 1600 times that of water. Could it be that when you shut it down some of your water flashes to steam in the hotter parts of the engine and over pressurizes the system ? 50/50 coolant has a boiling point of [I think] about 265°. It's expansion rate is also much less. I'd try filling it with the 50/50 the same way is said before and see what happens. That after all is what the system is designed to have in it. Anyhow...BE CAREFUL friend. Take it from an old maintenance engineer, that used to work on boilers, water flashing to steam is nothing to fool around with. ...J.D.
 

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2005 Spyder GT
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I did what you guys have said. Filled the rad (just water) to the top of the neck and the overflow to the cold mark. The gauge shows it gets to the three-quarter mark and then drops to just below half. Then, when I stop, it pukes out onto the road. Has done this repeatedly ... I have no clue why this is happening. When I changed out the intake, that got rid of my fast idle and the car runs really well other than spilling out the coolant.
Ok, I might be mistaken about this, but I seem to remember another post about what rad cap to use with the Moshimoto rad. I think someone said they were having trouble with the cap that came with the Moshimoto rad.
For just a few bucks, changing the rad cap might solve your problem. For what it's worth, my car has NEVER gone above halfway on the temp guage, and I'm still on the factory rad @93k.
(Now of course I probably just jinxed myself...LOL)
 

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2001 Spyder GT. Koni adjustable shocks. cold air intake, ST sway bar.17X8.5 rims. LED headlights.
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Temp stays pretty stable while an engine is running, but when you shut it off you are no longer disapating engine heat through the radiator. The heat of combustion in the upper part of the engine heat soaks into the water jackets causing the coolant temperature and pressure to rise. If you are using plain water to test that system, there is a real possibility some of that water in the cylinder heads could be flashing to steam causing it to overflow. ...J.D.
 

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Sounds like you got an air pocket in your system. I run a mishimoto also. You have to make sure your inside temperature it is turned all the way to hot while refilling the system. I flushed my whole system and mixed only 2 gals of antifreeze like the fsm called for and no problems.
 

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2001 Spyder GT
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Discussion Starter · #47 ·
The cap that came with my Mishimoto rad is rated at 19lbs...
I have got so many different answers to why I am overheating. While the car is no longer spitting out the antifreeze, the car still runs hot. I am wondering if it has anything to do with me having my intake powder coated. Obviously, this would contain the heat more than a plain intake? Maybe the thermostat failed?
I'm going to take it for a drive this morning and see what codes come up...maybe that will give me something to go on?
The car seems to run great...idles at about 800 and has no hesitation with lots of power.
I really appreciate you guys... it's like having your own team, just like the NASCAR crews.
 

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I am wondering if it has anything to do with me having my intake powder coated.
No, the intake plenum doesn't impact the engine or coolant temp.

Check the engine temp seen by the ECM using your OBD reader, and compare it to the cockpit gauge. The radiator fans should come on when the ECM reads 230°F. What does the gauge show when the fans come on? I'd expect it to be at "medium" with the needle about horizontal. It's possible your coolant sensor isn't reading correctly and the fans aren't coming on until the coolant temperature is too high.

If the fans are working properly and the two temperature readings are about the same, I'd next remove the thermostat and run the car without it to see if the problem continues. Check that the thermostat was installed correctly, with the spring on the engine (hot) side, and the jiggle pin towards the top. Drive the car without the thermostat. If the problem goes away, replace the thermostat. Otherwise reinstall the thermostat and move forward.

Next I'd check for exhaust gas in your coolant. Free-rent an engine block tester from a chain auto parts store. It presses against your radiator neck and will detect a head or block leak. You'll have to spend $20 on a bottle of test fluid but it will last you many tests.

If all of this looks normal, I'd replace the water pump next.

I skipped flushing the cooling system because I can't imagine a plausible way that scale buildup would cause what you're seeing, where the engine overheats and then drops. But if you're going to replace the water pump and drain the system anyways, I'd run a radiator descaler first so it's all clean when you reassemble.
 

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2001 Spyder GT
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Discussion Starter · #49 ·
The car gets up to the three-quarter mark and then drops a little below the horizontal mark. Something I noticed today... I pulled the plug off the top of the sensor with the dual wire...the plastic part of the sensor turns a little... I didn't want to turn it too much, but that should be solid, I believe... I have a new thermostat and gasket, so I will install that and see what happens.
 

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2001 Spyder GT
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Discussion Starter · #51 ·
I’m happy to say my car is no longer overheating. It was the thermostat... Just because you put a brand new one in does not mean it's going to work. The part must have been defective right from the start. I know I’m going to sleep well tonight because I have been tossing and turning these last few days. Thanks to all who gave input...
 

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2001 Spyder GT. Koni adjustable shocks. cold air intake, ST sway bar.17X8.5 rims. LED headlights.
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It happens. I was beginning to wonder if the thermostat was installed correctly. I used to own a Dodge truck that would allow the temp to rise way above setpoint before the thermostat would finally open and cool it down. I used an old hot rod trick and drilled a 1/8" hole in the thermostat to allow a trickle of coolant through. That solved it. It was a design flaw on that style engine [no coolant bypass port]. ...J.D.
 

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2001 Spyder GT
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Discussion Starter · #53 ·
The failed thermostat was installed correctly, but that thing was garbage. I put the new thermostat in boiling water, and it opened right away... I did the same thing with the one I removed, and it would not open. As far as the sensor plastic part moving, a little bit does not affect its operation because the gauge and fans are working. Now that the overheating problem is fixed, I can get these mufflers hooked up. Sitting in the grass at the car show they look very low to the ground, but on the road there is plenty of room.

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