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EJ25D Runs After Rebuild, Still Overheats


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If you've been stalking my posts over the last few months, you know that I rebuilt my EJ25D in a 98 Legacy Outback due to a perceived head gasket failure and overheating. I replaced the HGs, Waterpump, and Thermostat while I was doing this to eliminate any possible problems in the future.

 

Well today I started her up and smiled like a giddy school girl in a beauty pageant. However, the engine started overheating. I figured it didn't have enough coolant, so I slowly added more and more, hoping to burp out the air bubbles. This helped, but didn't stop the coolant temperature from overheating.

 

It suddenly occurred to me that I had fixed the damage done by the overheating, but hadn't actually found the cause. I just assumed it was the head gaskets because that seemed logical (and the gaskets were pretty bad when I took them out).

 

So back to the drawing boards. Is there anything you guys can offer me that might help? Anyone else have this problem? Anything I should watch out for?

 

TL;DR: EJ25D's overheating. Replaced the head gaskets, water pump, and thermostat. What do I do?

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Is your thermostat in upside down or bad maybe?

 

As well, clogged radiator may be an option.

 

Most likely though, you need to burp (bleed) your coolant. There is probably a big air pocket in there after all the work you did making it overheat on you. Its not necessarily the same overheating problem you had before. You pretty much replaced 90% of the cooling system, so chances of there being something actually wrong are pretty slim.

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Is your thermostat in upside down or bad maybe?

 

As well, clogged radiator may be an option.

 

Most likely though, you need to burp (bleed) your coolant. There is probably a big air pocket in there after all the work you did making it overheat on you. Its not necessarily the same overheating problem you had before. You pretty much replaced 90% of the cooling system, so chances of there being something actually wrong are pretty slim.

 

It's been burping slowly but surely. every time coolant was added (after it went down because of the burping) the temp gauge would go down to normal. Also, the top rad hose is hot and the bottom one isn't, indicating (according to the haynes manual) that the thermostat is allowing coolant into the engine and back through.

 

The thing is, the top hose feels as if there's no liquid. Also, when the screw cap thingy on the left side of the radiator was removed, car was started, and the car started to over heat, it volcanoed coolant out of that hole. Don't know if that's important or not, but there it is.

 

Anyway, how long should it take to burp the cooling system, generally speaking?

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I saw that, but I was confused as to what anyone was talking about. How do I BURP the coolant system, not replace the coolant and thermo altogether. Would jacking the car up work along with the hose squeezing, coolant topping off, and other crap?

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once you trap air in the system it can be very difficult to remove. i really do not know exactly how to do it short of draining it down.

 

i do know when the system is empty, if you remove the vent plug and fill the system SLOWLY you will dramatically reduce the possibility of trapping an air bubble.

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Burping is a SLOW process & it took me about an hour & some change to fully burp my engine after replacing the head gaskets & engine block. The vent that Johnegg has mentioned works. It will take a while but I used that same method to burp my engine. Just keep an eye on the thermostat as you are burping & you should be good. When you're done, the needle should read no more than half.
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Well, is it possible that this problem would suddenly arise on the highway? It seems as though this is exactly what I was going through before I did all of this work, only this time it didn't OVERheat, just keeps getting too hot. Would head gasket failure render this kind of problem?
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once you trap air in the system it can be very difficult to remove. i really do not know exactly how to do it short of draining it down.

 

i do know when the system is empty, if you remove the vent plug and fill the system SLOWLY you will dramatically reduce the possibility of trapping an air bubble.

 

The first time I did the coolant in my gtb I filled extremely slow, fair to say I had 0 air bubbles o-o I didn't do hg's or anything like that though

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Well, is it possible that this problem would suddenly arise on the highway? It seems as though this is exactly what I was going through before I did all of this work, only this time it didn't OVERheat, just keeps getting too hot. Would head gasket failure render this kind of problem?

 

Yes. If there is still air in the system, the temps will rise out of nowhere. As long as your exhaust doesn't smell like coolant, which it should not provided that you TQ'd the head bolts down correctly, then there must be air trapped in the system. Either that or your thermostat has an issue. While you're checking everything, see if heat is coming on when you turn on your HVAC system. Set it to as hot as it will go.

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Yes. If there is still air in the system, the temps will rise out of nowhere. As long as your exhaust doesn't smell like coolant, which it should not provided that you TQ'd the head bolts down correctly, then there must be air trapped in the system. Either that or your thermostat has an issue. While you're checking everything, see if heat is coming on when you turn on your HVAC system. Set it to as hot as it will go.

 

... What's the HVAC system? How do I set it? lol

 

i know this sounds like a lame thing, but how old is your radiator cap?

 

Idk probably as old as the car. I only had it a month before it crapped out.

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Does anyone know if he can do a pH test on the coolant to check if there is carbon-monoxide entering the system passed the seals?

 

Other than that to be on the safe side I would drive it close to the mechanics location for an hour maybe longer. If it starts to overheat again you have a lower towing cost.

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It helps burp the system?

Yes mine didnt take long at all. I started it up with the cap off and filled when needed then squeezed the upper hose a few times till it was starting to boil over then put the cap on and squeezed the hose a few more times then the temp stabilized. Before hand make sure you get as much coolant in the radiator as you can.

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