98 Legacy Overheating ~ Air, Stupidity or Head gaskets

Recently I have been dealing with a cooling issue in my 98 Legacy. To understand everything about it first you have to know that my original engine in this car started misfiring but luckily I had a spare engine that was sitting in my friend’s warehouse for a couple of years. This 'new' engine had around 130K miles on it and upon inspection it appeared to have had the head gaskets (metal gaskets) and timing belt replaced. I had also replaced the timing belt, water pump etc., a year prior, on my original engine. So a few weeks ago I swapped my original engine for this 'new' engine but I did not swap the timing belt components or water pump because I did not have the correct gaskets at the time. Put everything back together and drove it 100 miles back to my house without any issues.

 

Fast forward a week or two where my car was on jack stands while I was replacing ball joints, tie rod ends, a steering knuckle and my handbrake, and I was finally ready to get my car back on the road. I drove into Boston (About 30 min with traffic) without an issue, however on my way back, when I got off the highway and back into my town, my car started overheating. I pulled over and accessed the situation, my radiator cap was spewing fluid, the top radiator hose was collapsed and I could hear my coolant boiling in the top radiator hose and beneath the radiator cap. While letting my car cool I could hear air rushing into the system via the radiator cap. So after I got home I got into my brothers car and drove to an AutoZone and bought a new radiator cap. I got home and burped the car a little (not enough) and put the cap on.

 

On the next day after work I decided to test the car once again, this time just driving around town and of course after some driving my car started to overheat again but this time nothing was coming out of the radiator cap but I could hear my coolant boiling again. I on my way home I noticed it would overheat a lot less at 3000 rpms or so unless I was climbing a hill, I believed this was all because of air being trapped in the system still.

 

The next day I bought a zero spill funnel for burping the system from NAPA and proceeded to burp my car for an hour and a half or so, I don't think I ever got out every single air bubble, it was still sending out one every once in a while but I did get out a ton of air that was in the system. To burp it I was parked on a slight incline with my car facing up the hill, I had the heat turned all the way up but with the fans for the cabin turned off. It did not overheat during this whole process, the fans attached to the radiator work well also. *I do believe I may have put too much coolant in the reservoir*

 

So after burping it for so long and then letting it cool down I then drove to my friend’s house about 16 miles away. I was going 70 - 80 mph on the highway and then there was a massive amount of road work and I was stuck in stop and go traffic for a very long time but within that whole time my car did not show any signs of overheating and worked perfectly fine all the way to my friend’s house. On the way home from my friend’s house I was driving alongside another friend of mine and trying to keep up with him, which in retrospect was a very dumb idea but I’m only 21 so what else would you expect. I was definitely pushing my car harder than normal, doing pulls on the highway in 4th gear and going an average of 80 - 90 mph the whole time until my car decided it was not having a good time anymore and started to overheat. I pulled off the highway and found a spot to park my car, popped the hood and found coolant all over the driver side of my engine bay. It was not hissing and I could hear no boiling. It appeared to have come out of the reservoir which was now empty. So I waited for a little, put some coolant in the reservoir and drove home. For most of the drive home my car was running at a good temp but at times it would overheat a little, enough to make me stop a few times but not every time, and then return back to normal operating temps, it was like a pocket of air would go through the engine ever so often causing it to overheat. When I got home the level of coolant in the reservoir had dropped. I also tried to see if my car would overheat when it was idling and it would not. I kept it running for a decent amount of time to see but it never overheated again once I got home. That all happened last night and this morning when I checked the reservoir it was empty again, the car had wet spots underneath it but I think it was from how soaked everything was in there and not from a leak in the reservoir (but I will check that better later).

 

I'd like to think that all the coolant blew out of the reservoir because of my speedy driving/ high coolant level in there but I don’t really know if that would cause the whole reservoir to blow out and not just the excess. Also I was wondering if air gets sucked into the system via an empty reservoir. This weekend I plan on removing my radiator and replacing the water pump / all of the timing components from the ones on my original engine. I am getting another new thermostat and radiator cap from Subaru. Once I replace everything I am going to flush the coolant system and the radiator. I am really hoping this issue is just from air being trapped in the system / from my own stupidity. Is it possible for the reservoir to blow out all its fluid, causing it to overheat, from it being over filled and from driving at high rpm’s with high load? What tests should I do to see if the HG are at fault? ~ Thanks for reading

Edited July 19, 2019 by Nohenns

Well, seems to me air shouldnt just keep coming into the system when you were burping.

Things i would check,

Radiator and hoses for cracks, leaks.

Refill to proper level, and from cold, start the car without the radiator cap and see if you see air bubbles come up and out of there... You should not.

Also check your oil and make sure its not getting milky.

What thermostat is in the car? Subarus are very picky with cooling systems (As you now know) If there is anything other than an OEM brand and temp thermostat in the car, replace it asap. Also what coolant are you using and did you mix it yourself or premix? Also which engine is in the car now?

I may have phrased what I said about the burping poorly

 

'I don't think I ever got out every single air bubble, it was still sending out one every once in a while'

 

The amount of air leaving the system drastically reduced over time and to a point where I could rev up the engine and squeeze the top radiator hose with no air bubbles coming out. The radiator has always had a dark spot that I have always been suspicious about but it has been there for at least 4 years and I have never had a cooling problem before but hey things break, I will have to investigate up close.

 

The weird part of this is just how I was going 80mph then immediately was stuck in stop and go traffic and everything was perfect but then on the trip home my whole reservoir puked all over my engine.

 

Also wouldnt bubbles surface if more air got sucked into the system, it makes sense to me that air would get sucked into the system if the reservoir was empty and if the engine just cooled down even a little bit. Or are you thinking the bubbles would have already surfaced?

 

Thank u tho that's all good advice , I definitely should have already at least looked at my dipstick at this point

I have no idea what thermostat is in the car right now and I do intend on putting in a new Subaru one when I do the timing components/ water pump this weekend, sadly I have very little knowledge about the engine I have in my car right now which is the engine that sat in a warehouse for a few years. The coolant is prestone and I mixed it myself 50/50 with distilled water. I plan on getting concentrated Subaru coolant and mixing it myself with distilled water again.

Any tips and tricks on flushing the coolant system? Should I remove the thermostat when flushing the system? Should I flush it after replacing the water pump/thermostat or before? I've never done it to my car when I definitely should have done it ages ago...I should probably change my gear oil as well... Edited July 19, 2019 by Nohenns

More concerned now with it being the head gasket. Saw a consistent stream of small bubbles coming up through the funnel in the radiator at times also there was small amounts of oily residue floating on the top. It explains why the engine overheated under load as well and why it is so erratic right now, these all are the early signs of this failing I've learned .... https://allwheeldriveauto.com/subaru-head-gasket-problems-explained/

 

This site has a nice write up

If it's had a bunch of new coolant through it recently, I don't think a coolant flush is necessary since it's probably safe to assume the stuff left in the system after it's been drained will new coolant. When you go to bleed the system, jack the front of the car up and have the heater on max when you do it. That way you can ensure the bubbles are out. Also once the new thermostat is in, back fill the engine with fresh coolant via the upper radiator hose.

I think I'm gonna take out my engine and do the head gaskets....Irrational? probably , the oily stuff in the coolant is enough to spook me

I had a parts store thermostat give symptoms like you are describing for the driving part.

 

However a steady stream of small bubbles at the cap while idling sounds like head gasket.

YAY! I'm not an idiot, my head gasket is indeed blown. I was terrified that I'd take off the head to find a head gasket in good condition. I also discovered my timing was off by a tooth on one of my cams

Off by one tooth is disappointingly common. Putting the belt back is a lot easier with an assistant.

Yes I found that to be the case when I put it on my motor that developed the misfire, luckily that motor did not jump a tooth.

 

Time to resurface the heads and possible the block, going to be using a nice flat granite block that my brother owns along with a nice straight edge to check for flatness.

 

Any advice or threads anyone would like to share would be appreciated. I have been doing my research so I think I have a good grasp on what I am to be doing but could still use tips and tricks

Wear some breathing protection when working with aluminium dust.

Good to know, hopefully not much will be in the air since the sand paper will have copious amounts of WD40 but if you did not say that then I would have otherwise not have worn anything