2G Overheating, coolant pressure

Dihtung Glava · May 16, 2022

Hi, so I've been passionately searching this forum for the past week, ever since I bought my '99 2G 4G63T(out of a 1g) swapped eclipse, looking for a thread that would pose a similar problem to mine, but I haven't found one, so I'm writing my own now.

It all started when I first bought the car and drove it home. Pushing it up a nice curvy hillside road, the car blew almost all of it's coolant out of the overflow bottle and overheated towards the top of the hill. I stopped, got some water from a nearby restaurant and carefuly continued. I kept my eye on the temp gauge the whole time and, as it was staying in the bottom half, I thought I was in the clear. I let it hit boost a couple of times when I finaly drove into my town (which was probably stupid, I know) and it overheated again, just as I pulled into my driveway. All and all the trip was about an hour and 30 minutes, with the first overheat happening around 25 minutes in...

I found the radiator cap wasn't holding very well, so I got a new one the next day. This one, rated for higher pressures, holds nicely. The problem is now the entire cooling system is under a lot of pressure. The top radiator hose is rock solid after a couple minutes of driving and the coolant overflow bottle is constantly beeing filled, not so much when cruising, but if I floor it, it'll fill up in a couple minutes. So I'm guessing the coolant (which is about 50% water since I last filled it up) is constantly boiling or, there's just way too much pressure in the system, or you know, both.

So If anyone had something similar happen, what did you need to fix/replace?

randman2011 · May 16, 2022

How does the oil look? Have you performed a compression test? The first (and only) thing that comes to mid for me is a blown headgasket pushing combustion gases into the coolant passages once the engine gets warm.

How good is the heat in the car? Can you confirm that coolant is actually flowing?

pauleyman · May 16, 2022

There are basic diagnostic tests you should probably run. Coolant pressure test, compression, leak down. If the coolant is being pressurized there is a problem somewhere. I'm going to suggest head gasket also. The tests I mentioned will find it. That isn't the only possibility.
Please fill out a profile. give us a much information as you can on what you are testing and we will try to help.
Might help if you give us some info on your own mechanical ability.

T bags · May 16, 2022

Does your Autozone rent out compression testers? If so start their since it’s free. Try getting a picture of the antifreese color and oil to see if any leakage

Dihtung Glava · May 16, 2022

T bags said:
Does your Autozone rent out compression testers? If so start their since it’s free. Try getting a picture of the antifreese color and oil to see if any leakage

No autozone in Slovenia

I am hopefuly seeing our resident mechanic this week though, so hopefuly he's got the equipment. The coolant color is brown atm, I'm assuming that's cause it's mostly water and the pipes are rusty? And yeah, my friend and I spotted a tiny oil leak at the edge of the valve cover when I brought it to his shop to put it on a lift and I'm doing that gasket this week as well, though it doesn't seem too bad as the oil level has not moved since I last checked it.

AWD-Tony · May 16, 2022

Leave the coolant cap off when you perform leak down test to check for bubbles.

Dihtung Glava · May 16, 2022

pauleyman said:
There are basic diagnostic tests you should probably run. Coolant pressure test, compression, leak down. If the coolant is being pressurized there is a problem somewhere. I'm going to suggest head gasket also. The tests I mentioned will find it. That isn't the only possibility.
Please fill out a profile. give us a much information as you can on what you are testing and we will try to help.
Might help if you give us some info on your own mechanical ability.

Alright, thanks. I'll fill out my profile as soon as I can, I just made the account on my phone during class today, to put out my question as soon as possible.

I'll also update you on the car as soon as there's anything to report. As far as my mechanical abilities go, I took an interest in cars somewhat late, so I've been trying to learn as much as I can now.

So I've been working on vehicles when I have time, but not so much on cars. I can do the standard oil change, wheels or brakes, but other than that I'm pretty fresh when It comes to cars.

T bags · May 16, 2022

You’ll be fine. It’s a good platform to wrench on and the forum is supportive

pauleyman · May 16, 2022

I wouldn't bother with the valve cover gasket yet. You would be wasting rime if you find bigger problems elsewhere. Run the tests and see what's going on. Your coolant shouldnt be brown.
Was it green when you first got it?

Dihtung Glava · May 16, 2022

pauleyman said:
I wouldn't bother with the valve cover gasket yet. You would be wasting rime if you find bigger problems elsewhere. Run the tests and see what's going on. Your coolant shouldnt be brown.
Was it green when you first got it?

Yeah no, as I said the little valve cover leak is not a priority until the car runs as it should. Yeah, the antifreeze I put in was blue at first, but as I said it's mixed with a lot of water so that's probably picking up rust right?

pauleyman · May 16, 2022

Dihtung Glava said:
Yeah no, as I said the little valve cover leak is not a priority until the car runs as it should. Yeah, the antifreeze I put in was blue at first, but as I said it's mixed with a lot of water so that's probably picking up rust right?

Unknown but blue coolant is not the spec for these cars. Do you know how much water is in it vs coolant?

Dihtung Glava · May 16, 2022

pauleyman said:
Unknown but blue coolant is not the spec for these cars. Do you know how much water is in it vs coolant?

realy? I didn't think it would matter that much or, at all... what is the right coolant for these cars? No, I don't know what the mix ratio is sadly, I just filled it up after it blew out, my dad took it to work one day testing it too and did the same so I have no clue, but If I had to guess I would say like 75% water?

T bags · May 16, 2022

Was the bottle that you used 50/50?

95_gsx_2g · May 16, 2022

As for Valvoline coolant the red and blue zerex is compatible with Mitsubishi. Check and fix any leaks like bad or dry rotted lines loose clamps etc. Sounds to me like you have a faulty thermostat if the problem still persists.

Dihtung Glava · May 17, 2022

95_gsx_2g said:
As for Valvoline coolant the red and blue zerex is compatible with Mitsubishi. Check and fix any leaks like bad or dry rotted lines loose clamps etc. Sounds to me like you have a faulty thermostat if the problem still persists.

Interesting, so you don't think it's the head gasket?

Dihtung Glava · May 17, 2022

T bags said:
Was the bottle that you used 50/50?

No, just a random mix of coolant and water... I didn't think about it too much, as I feared It's the headgasket's fault early on, so I knew we'd probably have to open the engine and change all the fluids then.

Mech Addict · May 17, 2022

Less coolant in the mix will boil at a lower temperature. Your gauge wasn’t reading high, so perhaps it’s not overheating, just over pressuring. You can also remove and check the temp sender resistance. I would suggest you drain the cooling system, replace the thermostat, hoses, and clamps as needed, and retest. Those are all relatively cheap, and smart for any used car you just obtained.

Mech Addict · May 17, 2022

NOrmal mixture is 50% pure ethylene glycol based engine coolant, 50% distilled water.

Kryndon · May 17, 2022

Hi and welcome! Sort of unrelated but when I was in Kranj I had the best McDonalds with the best view, the one at the Eastern part of town near the Interspar, f***ing loved Slovenia every bit of it, only saw Evos though, not a single DSM

The others have given good advice. As for coolant color blue is actually fine, personally I use one of the best brands on the market, HEPU, a German brand, 70% distilled water and 30% coolant. Before that thorough flushing is advised.

Is your car stock? Any front mount intercoolers or aftermarket radiator fans? Have you double checked if your fans switch on when the car is idling and warmed up? A 1.1bar aftermarket coolant cap is a great upgrade without overpowering the stock components. Keep in mind that a clogged radiator and system or a bad mix could still result in overheating but okay temps while idling or light cruise. Boost simply loads the engine that much more. Start with the easy and cheap things and don't worry about a blown gasket just yet. Most times there would be other symptoms such as oil-coolant mixing, smoking out the back etc.

P.S funny nickname, let's hope it stays as a joke :pray:

Dihtung Glava · May 17, 2022

Thanks for the welcome haha, everyone is so nice here. Yeah I know which McDonald's you're talking about, it's right on the edge of town so there's only fields in one direction which look realy nice in the evenings. It's been a common spot for us to hang out at since like, forever. Do check out the Pinki fast food place near there if you ever visit again, now those are the best burgers around.

And yeah the current status now is - I'm meeting my mechanic wednesday next week to perform all the tests the guys mentioned so far. I mentioned the coolant to him as well and we'll flush that too.

The engine is basicaly stock but since it's out of a 1g eclipse, I guess that means the car isn't realy stock huh? Whoever did the swap, left the OG fans on and just wired them both to run all the time so I guess that's not why we're overheating. Are you sure this wouldn't be the head gasket though? I mean, since the cooling system is almost instantly pressurised? Don't get me wrong, I would love for it to be just a faulty thermostat or something, but my dad seems dead-set on his diagnosis of it being the head gasket and will just debate me instantly if I bring up anything less severe XD. I guess we're just waiting untill wednesday for now as I'm busy with uni anyways

Yeah this nickname is probably gonna be the most ironic irony in the history of time if it ends up being the head gasket, as it's been my videogame username long before I got this car

T bags · May 17, 2022

Sounds like his instincts are kicking in

mattsipple · May 11, 2023

In reality, what coolant color is correct for 2g dsm? I've seen at least 3 different colors in this thread and can't seem to find a telltale answer to which color it should be.

Spleen8urLSX · May 11, 2023

mattsipple said:
In reality, what coolant color is correct for 2g dsm? I've seen at least 3 different colors in this thread and can't seem to find a telltale answer to which color it should be.

I dump the cheapest green shit from Rural Kings in mine, their Providence house brand 50/50 (6 bucks a jug). Normal green antifreeze is what it had in it in 1992 when it was new and hasn’t hurt it yet over the course of 31 years. I only put coolant in it when I put it away for winter storage, then if I don’t tear it apart that same cheap green coolant stays in it until the first time I go to the track for the year, then it gets all drained out and replaced with straight distilled water as that’s what the track rules call for (that’s any drag strip you go to, and someone always blasts coolant everywhere when they break something, then they get to be the asshole that shut the track down for an hour because they have to clean coolant off the track) and that’s what stays in it until it’s time to put it away again. Never bought any fancy coolant for anything I own, just the cheapest thing I can get that’s the proper specification. Coolant is coolant as long as it’s the right kind for the application, brand makes absolutely zero difference unless paying for a certain name helps you sleep at night.

mattsipple · May 11, 2023

Spleen8urLSX said:
I dump the cheapest green shit from Rural Kings in mine, their Providence house brand 50/50 (6 bucks a jug). Normal green antifreeze is what it had in it in 1992 when it was new and hasn’t hurt it yet over the course of 31 years. I only put coolant in it when I put it away for winter storage, then if I don’t tear it apart that same cheap green coolant stays in it until the first time I go to the track for the year, then it gets all drained out and replaced with straight distilled water as that’s what the track rules call for (that’s any drag strip you go to, and someone always blasts coolant everywhere when they break something, then they get to be the asshole that shut the track down for an hour because they have to clean coolant off the track) and that’s what stays in it until it’s time to put it away again. Never bought any fancy coolant for anything I own, just the cheapest thing I can get that’s the proper specification. Coolant is coolant as long as it’s the right kind for the application, brand makes absolutely zero difference unless paying for a certain name helps you sleep at night.

Great! thank you so much glad we cleared the air on that

Spleen8urLSX · May 11, 2023

mattsipple said:
Great! thank you so much glad we cleared the air on that

No problem! Though I’m sure someone will disagree or argue it no brand of coolant is going to do anything different than the next, and as far as what I’ve found it’s never cared what’s in it, run’s at the same temperatures whether there’s distilled water in it or $6 a jug coolant, and almost every time it’s been on the dyno is also with cheap ass coolant in it. For the 2g I don’t remember if Mitsubishi called for standard green coolant or moved on to something else but it’s all the same engine and essentially the same cooling system nonetheless, for what it’s worth I wouldn’t hesitate to fill it with the “universal” yellow stuff many newer cars use as it meets the same standard as the old school green stuff, I just don’t as I get the green stuff even cheaper.

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