98GT

No, I didn't. I ran out of time that day, then went hunting again for a couple of days. While I was gone, my son made a verbal even trade for a 04 Crown Vic Police interceptor LOL. And I think that transaction is going down tomorrow. So that will officially be the end of this story. I appreciate everyone's input and help on this issue. I updated my first post on this thread to reflect the end, to no ending solution, as I hate reading a lengthy thread only to not find a solution.

So why would they never work for subaru's? This takes me right back to thinking does anything but Subaru work with Subaru? I've had this engine out multiple times. If its the HG's, I'm cutting my losses and being done with it. Maybe he can part it out and make $500 to put down on another simpler car.

Just did another test with engine cooled off. The kit says run it for 10minutes and then test it for 2min. I tested it for 10 minutes with no signs of color change. After that, the system pushed coolant into the tube again. If this type of test is accurate, then I'd say there is not combustion leak, indicating no head gasket leak, right? I am going to do the heater core test next. idosubaru, I'm pretty confident the radiator is not clogged. You can go back to the first post with the video of the water exiting the lower hose, and give me your opinion on it.

new status report. I took it to town, and it still indicated hot by nearly pegging out the gauge. I took temp readings before at normal operating temps for a base line, and again when it was "overheating", with the upper hose swollen. I use quotes because the highest temp I saw was the top center of the engine block at 215*, the heads were 180-190*, the upper hose was 170* , the temp sending unit (which is new) was 179*, and the lower hose was only 80*. I bought a combustion leak detector while in town, and it is not playing nice. The system keeps pushing coolant into the tube, even though the radiator level is a few inches below the neck. The instructions say start out cold and run the engine for 10min before test, but I did it right after pulling in and it was hot. Which I figured was what I needed to do since it only has a problem once it's been out on the road. Any advice on how to make this thing work right? I'm all ears. I will be trying again with a cooler engine though. That does however bring me right back to the same pressure issue it was having before the thermostat swap. On a related note, the car runs great when the gauge is at normal temp, but starts losing power quickly as soon as the gauge starts to climb. What's the relation there I wonder? Thanks for everyone sticking with me on this one. https://flic.kr/p/2bx5VVT

Status report. Took it for a drive, after bring up to temp in the shop. I ran it in manual the entire time keeping the revs high for a couple miles. The gauge fluctuated between normal and high, but it never pegged and quickly dropped to normal range every time it went up. Once I pulled it back it the shop, and opened the hood, it was apparent that it did puke at least once, and the reservoir was full, which was at the cold level when I left. I'm letting it cool off with the front on the car elevated for awhile, then I'll drive it into town. It never got, or stayed hot enough to take temp readings with the gun.

1LT, I have not put any block test fluid. To be honest, I've never heard of it, and had to look it up. The first thing that came to mind was the ole blinker fluid trick lol. I got home late last night, and was cold from being in sub freezing temps for two days, so I didn't even consider going out in a semi cold shop last night. But I'm out here this morning, got the wood stove rolling and I'm fixin to tear into the shitbox again. Just to twist the knife in a festering wound, I found this when I came out this morning. Yeah. He's dreaming on the price, but at least I taught him to start high, because it's hard to get more that you ask for...

The overflow and cap are working properly. I've watched the level come up, then go back down several times.

The 45 prevents it from suctioning to the bottom of the overflow tank.

That's not a bad idea. The heat seems to work fine, so not sure it's blocked, but easy enough to give it a shot!

According to my son, it did not overflow or pull any from the tank this last "overheat". But before the thermostat swap, it was puking coolant.

Did the t-stat, and still over heating. It passed the first short test drive, on Monday, after I installed it. I was in the woods hunting yesterday, when my son took it for a longer drive, and it FAILED! However, he said the gauge pegged out on hot, then within 30 seconds, it dropped back to normal. I thought may be an air bubble passed by the sender, but he drove it again, and it did the same thing, however, he said the upper hose didn't swell this time. As soon as I get home from hunting this afternoon, I'm going to break out the digital thermometer again and get a couple more actual temp readings from the upper hose, the cylinders around the water jackets, AND the sending unit its self. The plugs may have been a little lighter in color. The plugs have less than 100 miles on them. Not sure how long it takes to get a true reading. As far as the heads, I did not have them machined, since the engine had no top end issues, and ran great until it spun a bearing. Plus, I checked them as well as the block for flatness. And yes, multi layer gaskets were used.

I'll call the dealer tomorrow and order one, and cross my fingers that it fixes the problem. I'm not a long time Subaru owner, but I just don't get why these cars are so OEM dependent. And why, if things like the thermostats are so sub-par, the aftermarket isn't forced to pick up their game to make better parts.

Murray, I believe. My boy bought a water pump today, but I'm still not convinced its the pump. I did spin it by hand when the belt was off, and It felt firm. Easy to turn, but no free spin. Are these made like a boat water pump out of rubber, or are they metal fins like the older domestic pumps?

Here's the skinny. The engine in my son's 98 Legacy continues to overheat after we did a short block rebuild. I have done all that I can think of to do as to figuring out what is causing it. The car warms up at idle-2000rpm just fine and cycles the fan and thermostat normally. But when I take the car out on the road, after several minutes, the gauge starts to climb and the upper hose gets swollen and really hot, while the lower hose stays very cool with no pressure on it. After turning off the car, you can hear coolant boiling in the engine and radiator, and it forces coolant out of the neck. into the overflow. Once it all cools down, it works like normal again until I drive it. Oh, and it starts running like crap once the temps go up. I've done several tests including looking for signs of a blown head gasket. So. now I'm looking for some help, before I roll it out in the field and set fire to it. No, seriously, I'm thinking of burning it to the ground, and cutting my losses. Here is what I have done: Flushed the radiator and had good flow. Replaced the new thermostat , with another and tested it before it went in. Jacked the car up, and burped the air out of the system, which it did have a good burp after it was up to temp and I revved it a few time up to 3-4k rpm Compression test. (Result: 190-200PSI) Leak down test. (Result: Pass) Coolant system pressure test with warm engine: (Results: System held pressure and had no sign of coolant in the cylinders) The only thing I haven't done is replace the water pump, which was replaced just before he bought the car. I haven't changed it, because I'm thinking with the pressure in the upper part of the system, tells me the pump is working. UPDATED EDIT: The solution to this problem was never found, as the car was traded off. However, there is a lot of good info here to guide you to a answer, if you're having the same problem, just no final solution. Here's a couple pics/video I managed to take Edit: The gold/brown stuff on the plugs, is anti seize, not oil

GD, I didn't add that the plugs, nor the pistons showed any signs of water intrusion, and the head gaskets are brand new, if that changes your opinion on anything.