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Overheating issue


swamp

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Hi guys

 

Car in question is a GF8 with an ej20g engine. 

 

Recently I disconnected my coolant fill tank when I removed my intake manifold for painting and I've had an overheating issue since. I've bled the system alot and I think I've got the majority of the air out of it. I am using straight water though but that'll be remedied when I do flush the system. 

 

Today (second day of bleeding) everything looked stable no air coming out of the coolant, so I fitted my rad cap and took her for a test drive with the temp gauge in usual spot. Not long after that, it overheated. Ive shut my engine off and given it a rest for five min and it has gone right back down to midway. It quickly rose though. 

 

The temp gauge does fluctuate, so does the tachometer intermittently, mainly when I was off throttle rolling downhill. That suggests to me I've reconnected something incorrectly. 

 

I am pretty confident I've reconnected coolant hoses from the tank properly - the one at rear leads to the metal bit on top of the engine beneath the manifold,  not to the block directly. I don't see any oil in coolant or coolant in oil. 

 

It could be an issue with my heater, as my a/c does not work due to a short. However my car was not overheating before when the heater was not working. 

 

Coolant does gush out once cap is removed Hot and steam. 

 

I'm at a loss as to what it could be. I'm guessing it's my half arse intake manifold job. I really hope I haven't hooked up an oil hose to where a coolant hose has supposed to go. 

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Bad news. I bled the car today with the front jacked up, but after getting the fans to cycle on and revving, the car overheated. With the rad cap off. This says to me it's not that there's an issue with air in the system. Im guessing I've mixed up hoses. From the tank, top one leads to the turbo. Bottom hose leads to the metal coolant 'tunnel'beneatj the intake manifold. I've forgot its proper name. I'll have to remove IM when I get back next week and have a look. 

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9 hours ago, Loren said:

How do you know it's overheating exactly... how high does the factory gauge go?

Just from looking at the temp gauge. It usually runs a tad over half way, which I guess is from being filled with more water than coolant, and because turbo Subaru engine bays are relatively Hot. 

 

It goes from anywhere between 3/4 of the way up to all the way up. Last night sat at just a bit under the highest point. 

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I don't think water is going to cause overheating in a situation where the car is standing still and the radiator is being bled. 

How much water have you put into the system? Is the thermostat opening? Do both the top and bottom radiator hoses

get hot? Does the whole radiator get hot or are there cool spots?

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1 hour ago, SpeedySub said:

What's the process you are you using?

There is a step by step instructions online that mentions about having the heater on to help clear air pockets. It can take a while to get to done fully

 

Is that a real thing though, because water flows through the heater core permanently... the heater/aircon controls just dictate where the air is sent...

i.e through the heater core or through the aircon core.

Edited by Loren
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39 minutes ago, Loren said:

 

Is that a real thing though, because water flows through the heater core permanently... the heater/aircon controls just dictate where the air is sent...

i.e through the heater core or through the aircon core.

Not really sure, but Ive read a few posts and threads and how to's and they all mention it. Might not be relevant anymore? can't hurt either way, unless your sitting in the car on a really hot day with the doors closed and window up.

 

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10 hours ago, SpeedySub said:

What's the process you are you using?

There is a step by step instructions online that mentions about having the heater on to help clear air pockets. It can take a while to get to done fully

 

This isn't absolutely necessary with most Subaru's, as they don't have a heater tap. But, as I was a mechanic once upon a time, it was always good practice. Plus Subaru's are known for air pockets. You can bleed all the bigger ones out, but over 1-2 weeks they'll self bleed all the other small ones - just keep an eye on the overflow bottle.

But by the sounds of things here - sounds like something bigger is afoot. 

 

With the thermostat - test it in a cup of boiling water: it's only two 10mm bolts to get the housing off of the water pump. Plus - the bleed valve needs to be placed at the top. The bleed valve helps bleed out air pockets behind the thermostat.

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On 10/9/2018 at 8:05 PM, Individualities said:

 

This isn't absolutely necessary with most Subaru's, as they don't have a heater tap. But, as I was a mechanic once upon a time, it was always good practice. Plus Subaru's are known for air pockets. You can bleed all the bigger ones out, but over 1-2 weeks they'll self bleed all the other small ones - just keep an eye on the overflow bottle.

But by the sounds of things here - sounds like something bigger is afoot. 

 

With the thermostat - test it in a cup of boiling water: it's only two 10mm bolts to get the housing off of the water pump. Plus - the bleed valve needs to be placed at the top. The bleed valve helps bleed out air pockets behind the thermostat.

I will test the thermostat then. If that's the issue I will replace - most people go with oem rather than aftermarket, right? 

 

I feel it could be something I did not reconnect properly, such as the coolant temp sensor, or something not connected to the coolant tube that runs below the intake manifold. 

 

It's weird that my thermostat may be at fault - I do have all/most of the symptoms of a bad thermostat - but it was working fine prior to the work done. I don't know if it could happen, but maybe all the water rushing out+air pockets acting on it killed my thermo which was probably on its way out anyway. 

 

Iwould replacing the radiator cap be a waste of money? 

 

I suppose it could be that I've connected a hose wrongly, it's sending coolant to the wrong place, and the thermostat is functioning fine but no coolant from the radiator is being sent to the engine. 

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2 hours ago, swamp said:

I will test the thermostat then. If that's the issue I will replace - most people go with oem rather than aftermarket, right?

 

Would replacing the radiator cap be a waste of money?

 

It needs to open fully. Not just partially.

Absolutely. Going original Subaru is the only way to go.

 

Not necessarily. They're not that expensive, and it rules out another possibility. About $30 IIRC for a Fenix one. Although if you need 2, it can add up.

 

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On 10/13/2018 at 2:42 PM, Individualities said:

 

It needs to open fully. Not just partially.

Absolutely. Going original Subaru is the only way to go.

 

Not necessarily. They're not that expensive, and it rules out another possibility. About $30 IIRC for a Fenix one. Although if you need 2, it can add up.

 

Dont you think it's weird though, that a thermostat would stop working as a result of the things I've done to the cooling system, even though it was working fine before?

 

I'm thinking if I go over the work I've done pull off IM and double check and everything's fine, the next step I should take is inspecting thermostat and rad cap. 

 

I've never had to troubleshoot overheating issues before. I'm just wondering if it is actually possible for a thermostat to go bad after filler tank has been disconnected. 

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UPDATE:

 

So today I pulled off the lower rad hose and managed to undo the two 10mm bolts on the water spout/thermostat housing(?). The coolant within my radiator was the colour of muddy water whereas when I was undoing the thermostat and had it removed the coolant was more green. Could've been a sign the two weren't mixing? 

 

Ripped off the thermostat and it was much harder than the internet would have you believe. Big hands tight spaces are no fun. 

 

Tested it in boiling water and it did not open up - im not sure if I did it right but I boiled it at high temp to get it as hot as I could. Still no luck. 

 

Im going to conclude that it is a stuck thermostat causing my issues! I'm not sure how it would be explained when I was overheating, but it would be cool to get a better understanding of it all. I'm guessing hot coolant got blocked at the thermostat, and the radiator was trying to send cool coolant through system.

 

I will order a genuine unit - does anyone know best dealership to get in touch with? 

 

I'll also get a like for like radiator cap. I really want an sti one but I've read the extra pressure is not good for non sti cooling system longevity. 

 

When I have the money I will also order some Subaru Oem coolant - something about different metals leading to corrosion... 

 

Til then I will run no thermostat and just water. Good thing she's not daily driven! 

Fyi I think my thermostat is non oem if anyone can confirm. On it is written 170N 23 43 STC / 56MM USA

 

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If you drive without a thermostat the engine will never reach the correct operating temp on the open road... unless your radiator is blocked of course,

in which case it will still over heat. I suggest you get it checked and get a new thermostat before driving it anymore.

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You're right. I've only ran no thermostat to see if that really does fix the issue. So far so good. Car has been bled and after 2 fan cycles and a little driveway test, no overheating. Only thing I haven't really done is a test drive. 

 

I won't be driving it at all, until I get a new thermostat, as well as flushing it and replacing the coolant(*water) in there. 

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  • 3 months later...

Hey all 

 

I've pulled off my intake manifold and checked that the two sensors at the back of the coolant tree are connected, which they are. From memory my car never overheated once I removed the thermostat.

 

I'm going to try reinstalling the intake manifold, coolant fill tank once I clean it, and new OEM thermostat and bleed it with 100% water in there. If it doesn't overheat then I will drain and refill with coolant. 

 

That means my issue was most likely the thermostat...

 

 

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  • 2 weeks later...

Got it done in less than a day the other week, I followed a great method on here - raising front, pouring in while massaging air out of hoses, then bleed with car on, revving every couple of mins, then bleed with cap on. 

 

My car now runs a few degrees lower than halfway but was creeping up when moving slow... I put that down to it self bleeding/overflow bottle needed refilling. Upper hose kinda leaks air when squeezed now, probably needs replacing soon! 

 

Anyway if anyone else is doing a bleed, look up the above method. It'll take you half a day tops. 

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