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Discussion Starter · #1 ·
Okay...So I spent about 2 hours today driving 10 miles, because I had to stop every 3 minutes, turn off the car, and let it cool down.

I'm in NY and today it was really cold, like 7ºF cold. I was driving without any spirited driving whatsoever, and the coolant temperature gauge gradually rose past its normal operating temperature level and went all the way to H. I blasted the heat as soon as I noticed the gauge rising above normal, but to my dismay it only blasted cold air at me. So I pulled over, let it cool down. Checked coolant, and it was empty. I had filled the coolant recently, so I had some left in the trunk and added it. Note that I added it directly to the reservoir, because that's what I thought I should do. Now that I look at the manual, it says if the reservoir is completely empty, to "remove the radiator cap and refill as required," which is something I didn't do. Also, the manual doesn't say how much coolant to refill into the radiator, just "as required."

Started her back up, and everything seemed fine at first. Sure enough, 3 minutes later went from normal operating temperature to H. Pulled over, cooled down. Started back up, drove another 3 minutes, pulled over. Etc.

It's a 2001 2.5 RS that I purchased less than 1,000 miles ago. The previous owner said a dealer did HG replacement and remilled the heads less than 15,000 miles ago.

As for history of this happening, it happened once before a few weeks ago again when it was extremely cold out. I checked the coolant and it was empty, and refilled it. Since it hadn't happened before or since, I thought the previous owner just didn't keep up on checking the coolant. And adding coolant fixed the problem that time (or maybe it was the fact that I didn't drive it again until the ambient temperature was warmer).

THOUGHTS?
 

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Meany Head
2000 RSC
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10,236 Posts
Top up the coolant at the radiator cap, and ensure the overflow has the correct volume.
Drive it, and keep an eye on the temp gauge.
Every morning, re-check your coolant at both the overflow tank, and the rad cap to see if there is any drastic changes. You need to discern any sort of pattern before a reasonable diagnosis can be established.

P.S. Putting coolant into only the overflow isn't ideal, as it won't suck any fluid into the radiator until your engine starts to cool down.
 

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2001 A.W. L
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you are loosing heat because there is no coolant in the system, your blower motor blows over a radiator of sorts in the cabin. This is why the car needs to be warm to get hot air.

When the engine is cold, remove the rad cap and top off the radiator. Start car (with cap off) and turn heat on high. Keep topping off the radiator as needed until it starts to overflow on its own. Then put cap back on. Fill up overflow to first line.

Make sure you are using premixed coolant!!

Look for any signs of coolant leaking... Check that the top coolant hose and bottom hose are HOT (be careful) after its been idling for a while.
 

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Discussion Starter · #4 ·
When the engine is cold, remove the rad cap and top off the radiator. Start car (with cap off) and turn heat on high. Keep topping off the radiator as needed until it starts to overflow on its own. Then put cap back on. Fill up overflow to first line..
Is this the standard way to fill the radiator? Seems...precarious.
 

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2001 A.W. L
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Welcome to the subaru world :)

This is how I have been doing it for a while now and it does well getting rid of those pesky air bubbles/pockets that can cause issues.
 

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I kill threads!
2000 Ver 6 STI - 1996 Gravel Express
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Ya, that's pretty standard. If you don't do this, you'll never put in enough coolant. That's probably the problem you're running into.

By turning on the car, the thermostat can open up and get fluid to flow through all the hoses, engine, heatercore, etc. Once that happens, the fluid level in the radiator is going to start dropping, at which point, you'll need to throw in more coolant.

As for overflow, you'll want coolant in there too. As time goes on, the air bubbles will come out of the system and it'll pull the coolant from the overflow tank to compensate for the space the air bubbles was occupying. It's not much, so having your overflow to the 1st line is more than enough.
 

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Discussion Starter · #8 ·
So I did as Joshua suggested, but I only added coolant to the radiator once before it began overflowing. The coolant level never went down after I turned the car on and blasted the heat. The level only went up (and overflowed so I shut the cap at that point).

Thoughts? Does the fact that the coolant didn't go down at all mean anything?
 

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2000,rs
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When you blasted the heat was it blowing hot/cold air? It sounds like your thermostat may be stuck shut if your coolant never goes down after you have started the car then it is not being allowed into the engine, heater core, etc.
 

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Premium Member
overdeveloped beater
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When things are cool to the touch:
Raise and support the front of the car.
Open rad cap and fill to the top.
Start the car and let it run.
Watch for the level to drop as the t-stat opens.
Top off level as it drops until you see no more bubbles or gurgles.
Turn on heater, observe air from vents.
Hot? with no more bubbles? good....almost done.
Hot? With bubbles? getting there....
Cold? feel lower radiator hose.....If hot you have a blockage. If cold your t-stat is still closed.

If the coolant belches over on the ground, let it go......keep an eye on the temps and watch for bubbles.

Once you have no more bubbles and hot air from the vents, close up radiator and fill resevoir to the full line. Mark that level for reference. Shut down the car, lower it and let it cool. Go check the reference line to see if the level is lower or higher. It should be the same if no more air is present. It is ok if it's lower, but don't let the bottle empty out or it will suck in air. Refill bottle to the reference line, restart the car and let it warm up to operating temp. Shut it down and let it cool. Check the bottle again......repeat until the level stays constant.

This is not a 10minute job......it may take half a day to make sure you have the system bled completely. If you have bad headgaskets, this is all for nothing except practice, because you will have to keep a close eye on the level and where it's going to.
 

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Discussion Starter · #11 ·
I've never gotten any bubbles, I don't think. What are the symptoms of bubbles?

When I filled the radiator and blasted the heat, the air coming out was surprisingly quite warm. So am I good, despite the radiator coolant level never going down?
 

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2001 A.W. L
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if everything is working fine, then you are good.

If you start having issues again, air is getting in your system, you have a leak or you have a clog somewhere.
 

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Green 97 OBS
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I've come up with a bit quicker way to burp your coolant system which looks to be what your problem is. I fill the radiator until it won't take anymore, then fill the overflow tank at least 1/2 full, I usually fill it all the way just so I can see the level better. Then I put my hand over filler neck of the radiator and squeeze the top radiator hose to push air out through the overflow then let go and the vacuum formed pulls coolant in to replace it. A few minutes of that gets most of the air out of the system, enough that will allow you to run the engine without overheating. Start and run the engine until it gets to operating temperature, maybe drive it somewhere then allow to cool completely off. Take the radiator cap off when cool and make sure the level is right below the cap which means there isn't a big leak or air pocket preventing the cooling system from allowing proper expansion and contraction.
 

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97 OBS
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I found that the best way for me to diagnose a coolant issue is to understand the way the system works.

When the car is cold the thermostat is closed, when it reaches a certain temp the thermostat opens to allow coolant flow.

The coolant in the engine gets moved by the water pump, it flows out the top of the engine when it is hot, to the radiator where it cools down, drops to the bottom and flows back into the engine.
The thermostat blocks the flow of coolant from the radiator until the coolant has reached operating temp, then it opens to allow the system to flow.
It stays closed just to help keep the coolant in the engine heat up faster.

So to diagnose your thermostat without taking it all apart and draining coolant just check the hoses.

When the car is cold and all coolant topped off in rad and overflow tank start it up.
Both hoses should be cold at first, and as it runs just the top should heat up.
If the bottom it heating up at all without being up to temp then the thermostat is stuck open.
Run the engine with the heat on full blast until it comes up to temp.
At this point the thermostat should be open and both the upper and lower hose should be hot.
If the lower one is cold then the thermostat is stuck shut.
You can also feel the heater core hoses, if one remains cold then it is most likely clogged, further testing can be done with the coolant drained.

But basically the upper hose should always be hot, and the lower one cold when gauge is cold and hot when gauge is hot.

Another check I look at (which is not guaranteed to be a reliable check or anything) but @ 2500 rpm your water pump really starts to flow, so when bleeding the system with the cap off the radiator see if it spins in the top of the rad @2500, some will be spilling out so a big pan like a concrete mixing bin works great. If it spins the coolant it should be good, if you really don't get any coolant flow then your water pump may be tired or a crappy plastic 2 piece impeller pump could of been used.

I really like Jaguar 1785's method of bleeding his system, like a cold bleed, I plan to use that in the future before doing mine. Thanks Jaguar!
I will add mine that I do also so you can see different methods. Its nothing special, just what I read to do here on the forums.

I open the rad and overflow tank, top off the radiator, fill he overflow to the full line.
I go to all hoses, rad feed and return, heater core feed and return, throttle body feed and return and if you have an iacv the feed and return of that too, I squeeze each on a few times until air bubbles stop coming out of the top of the radiator.
I then make sure again everything is topped off and the caps are off then start the car.
I put the heat on full and go around to ALL the hoses checking their temps and squeezing them burping air out. I check and recheck each hose while burping them as the car heats up.
I run the car until the radiator fan cycles on, at that point be ready with coolant because the level usually drops.
I then top it off while the fan is running and once the fan turns off I turn off the car and top off if needed then put the caps back on.
Next time you go for a drive check and top off the coolant if needed and continue to do so for the next few drives when its cold just to make sure all the air is out.

Sometimes I do turn off the heat an rev it to 2500 to get it to warm up faster, but that is after first working all the lines free of air and verifying they are getting hot (or staying cold for the lower rad hose)



Note: Some radiators have a bleed screw on the passenger side on the top. I find opening that when the car is cold and topping off the radiator is necessary to get air out of the radiator. But not all Subarus have that so if its not right on the top facing up but on the bottom then its just a drain valve.


And as for your coolant loss, if you really keep noticing coolant loss but cannot locate any leaks then you could have an internal leak into one of the combustion chambers, check your exhaust, see if its white or smells/tastes kind of sweet. Its hard to tell and bad for you but I sniff mine every once and awhile, you can also go the more scientific route and get a tester to test for coolant for exhaust gases. Also look for bubbles in the overflow tank for signs of a bad headgasket.
 

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Discussion Starter · #18 · (Edited)
Hello again everybody. Well, things have changed some since I last posted about this...

For about a month or two, adding coolant to the radiator once seemed to have fixed the problem. Then, the other day, we had an unusually warm day (like 60ºF) and my car overheated. Figures, I thought, that instead of overheating on the coldest days, it now decides to overheat on the warmest in months.

Anyway, I open the radiator cap to check the coolant level and add more if necessary, and I am greeted by a most unexpected sight. It is what appears to be a rust-colored paste lining the inside of the top of the radiator mouth (pictures attached).





So, my research has led me to conclude it is one of the following possibilities.

1. It is an indication that the coolant has not been changed in a long time and obviously requires it.

2. It is a indication that two different coolant were added and somehow reacted to create this paste.

3. A previous owner added some kind of sealant additive to the coolant, and after a while it turned into this paste.

4. HG is screwed.


Here's what I know. The engine did at some point blow a HG. It was remachined and the HG's were replaced both about 25,000 miles ago. Could it be that #3 is correct, and that the shop that did the rebuild didn't actually do a coolant flush? It seems incredibly unlikely, and arguably negligent, but is it possible?

What is my best course of action at this point? I was thinking I should take it to a shop FIRST to have them measure the pressure outputs of the four cylinders to make sure it isn't a HG issue. Once that is elimnated, I should just do a thorough flush of the coolant and replace it with new coolant (plus the Subaru-recommended additive). Is this the best course of action, or should I also have a shop do some diagnosing or inspection of the coolant system?

If this is the best course of action, is there any harm in buying non-Subaru coolant as long as I add the Subaru-recommended additive? Also, should I replace the thermostat or anything else while doing a flush?

Thanks everyone for your help.
 

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2001 A.W. L
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the subaru coolant conditioner that they recommend putting in is a rust color.

get your headgaskets tested out. Depending on how hot you let it get when it overheats the heads could have warped.
 

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97 2.5 obs, 98 Legacy GT Daily
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Thats pretty gross. But I agree with you, get the HGs checked out then get your system flushed. They may have tried some kind of HG stop leak before actually getting the gaskets replaced and it was stuck somewhere and has just recently found its way into your radiator.
 
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