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EJ25 overheating after rebuild


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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.

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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

Edited by 98GT
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headgasket but proper diagnosis is best.  it's always amazed me how cool that lower hose can stay on an overheating engine. 

you're positive the radiator isn't clogged? 

the block tester kits can give false negatives, but yours sounds bad enough hopefully it'll be accurate either way.

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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.

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25 minutes ago, GeneralDisorder said:

The CO2 color changing liquid kits NEVER work for Subaru's. Waste of time. Pull the heads - that's how you find the gasket leak on an EJ. If you have burped it, and it has a factory thermostat and radiator cap - and then you drive it and it overheats - the head gaskets are bad. 

GD 

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.

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I feel your pain, been there, like i said before, this is exactly what mine was doing after I changed the gaskets the 1st time. Sucks. But I put another 500 into it and so far it appears to have fixed it. My mistake was assuming that what was good enough prep work for other cars I had done, was good enough for this one. It was not, and also the Subaru gaskets. 

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46 minutes ago, 98GT said:

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.

I can't tell you why. I don't have that answer. I can only tell you that it doesn't work. Just like compression tests don't show gasket leaks, and block/HG sealer products don't work on Subaru HG leaks either. They JUST DONT. Honestly those coolant CO2 tester kits really require a TON of CO2 to work at all, and I haven't personally seen one work on any application - many of which had confirmed HG failures after tear down. 

GD

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Concur about false negatives on exhaust gas testers for radiator bubbles.  Fluid didn't change color.  I had the same problems sucking up coolant into the tester.  Had to use a turkey baster with a hose to draw down radiator fluid.  Gives a false sense of reassurance.  The only positive I got was on tailpipe gases...yep, its exhaust all right.  

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20 hours ago, golucky66 said:

Did you bypass the heater core yet and drive it?

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. 

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