Subaru EJ25 engine forester overheating after timing belt change

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Sep 4, 2022
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little off topic maybe.

I have done timing belt replacement (along with all pulleys, water pump, tensioners) on my forester 2011 with EJ25 DOHC turbo engine at 107k running.

I did accordingly with manual and Utube guys. And assembled back only to find out that it is now overheating when going for like 5km. When idling, it goes back to normal temp.
(Radiator was replaced a month ago.)

What could be the cause guys?

(I reused the coolant cuz its only a month old. But I spilled some and added 0.5L water instead, would concentrate of coolant degrade and cause this mild overheating?)

or any potential cause i can think off maybe overtightening new water pump? (really cant think of any other reason, help me pls)

Thanks for your reply
 

dalai

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Sounds like you might have an air lock somewhere.
Thank you for your reply.

with funnel full with excess coolant/water, i tried burping the system with engine on till reaching normal temp for about 10minutes.
Should I try burping even longer period of time?
 
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Thank you for your reply.

with funnel full with excess coolant/water, i tried burping the system with engine on till reaching normal temp for about 10minutes.
Should I try burping even longer period of time?

10 minutes is nothing. I try to burp for at least an hour. Make sure to squeeze all the hoses, take the engine up and down the revs a few times, turn heaters on and off etc etc.

I've started drilling a 1mm diameter hole in the thermostat when fitting also. Makes bleeding so much easier.
 

dalai

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10 minutes is nothing. I try to burp for at least an hour. Make sure to squeeze all the hoses, take the engine up and down the revs a few times, turn heaters on and off etc etc.

I've started drilling a 1mm diameter hole in the thermostat when fitting also. Makes bleeding so much easier.i
10 minutes is nothing. I try to burp for at least an hour. Make sure to squeeze all the hoses, take the engine up and down the revs a few times, turn heaters on and off etc etc.

I've started drilling a 1mm diameter hole in the thermostat when fitting also. Makes bleeding so much easier.
In your case, does air bubble still come for an hour?
 
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Pull the small coolant hose from the block off the throttle body, put it in a larger pvc hose so you can get it into a container, open the radiator cap and fill until a good stream comes out of that hose. Clamp the hose off and reattach it, run the engine with the cap off until it reaches operating temp then rev it to 3K for a short burst. Make sure there are no bubbles, fill it and close the cap.
 

dalai

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You need a cooling system bleeder like https://www.tooldiscounter.com/prod...G6giKI7-K8GQaZoX7WleOlOBzXNqhx7RoC-cUQAvD_BwE Takes care of the problem in 2 minutes.
It seems this bleeder needs compressor which i dont have.

I tried with small funnel from kitchen and when revving to 2K, coolant were all over hood, was that burping? or engine just do that when reaching higher rev?

I will buy big funnel kit and try again.
I saw in the morning that overflow tank was sucked to low level from full from last night. Does it mean its sealed and no air in the system?
(morning 30min drive has shown me that it still gets hotter :( )
Pull the small coolant hose from the block off the throttle body, put it in a larger pvc hose so you can get it into a container, open the radiator cap and fill until a good stream comes out of that hose. Clamp the hose off and reattach it, run the engine with the cap off until it reaches operating temp then rev it to 3K for a short burst. Make sure there are no bubbles, fill it and close the cap.

short burst means like 5-6seconds or for like a minute?
Does overflowing normal when revving to above 2k ? or was that the process of burping?
Yesterday i did bleed for an hour, no air was leaving after 30mins, but when i rev up to 2k, it was like fountain, overflowing. Was that burping, should i keep revving up and down till there is no more overflow?
 

dalai

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You burp it until there are no more air bubbles

The Lisle coolant funnel is awesome :)
Does revving to 2K always bring the water level in funnel up?
or should i keep revving up and down until there is no water rising when revving to 2K?

i did yesterday for an hour, when idling there were no more bubbles but still i failed
 
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Does revving to 2K always bring the water level in funnel up?
or should i keep revving up and down until there is no water rising when revving to 2K?

i did yesterday for an hour, when idling there were no more bubbles but still i failed

you fill it higher than the highest point of the cooling system. Fill the funnel at least half way. The bubbles will rise to the top. You do not need to rev it to 2k
 

dalai

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What brand of water pump did you use?
GMB, japanese made. for Forester 2011 with Ej25 turbo engine.

I think i might overtightened the water pump. would that cause overheating?

Today i touched lower and upper hose after 30min drive. Lower house was slightly cooler than upper, is it normal? does this indicate coolant is flowing?
 
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I don't think the water pump could be overtightened enough to cause that much damage. Being that the EJ25 is an aluminum block, I'd venture that the threads would strip out of the water pump bolts before it got that tight. How is the heat in the car working? Since the boxer engine in a Subaru sits so low the heater core tends to be hard to get the air out of. Using a vac and fill is the only way to refill the coolant in these engines IMO.
 

dalai

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I don't think the water pump could be overtightened enough to cause that much damage. Being that the EJ25 is an aluminum block, I'd venture that the threads would strip out of the water pump bolts before it got that tight. How is the heat in the car working? Since the boxer engine in a Subaru sits so low the heater core tends to be hard to get the air out of. Using a vac and fill is the only way to refill the coolant in these engines IMO.
Heater is working well, AC as well.

other thing is I reused the coolant and since i spilled some, i added water so its not 50/50, i think now its water 60/40 coolant. Would concentration cause overheating?

when going 50km/h heater turned on, it doesnt overheat, when i turn off heater it tends to heat up.
 
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Sounds like you’re close. If you have ramps, use those, or lift & jackstand the front as high as you can. Get the Lisle radiator funnel or equivalent, turn the heater full hot and on high, and then fill the Lisle funnel and pull the plug. I normally keep the funnel about 1/3 to 1/2 full since Subarus can run 5 minutes with no burps, then have a huge bubble come out that drops the level by 2-3” in the funnel.

I don’t know that it will take an hour; but most of mine have taken at least 15-20 minutes, varying the revs from 2500 or so steady, down to idle, and back up. Elevation of the cap location is absolutely essential if you’re burping a Subie.
 

dalai

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Sounds like you’re close. If you have ramps, use those, or lift & jackstand the front as high as you can. Get the Lisle radiator funnel or equivalent, turn the heater full hot and on high, and then fill the Lisle funnel and pull the plug. I normally keep the funnel about 1/3 to 1/2 full since Subarus can run 5 minutes with no burps, then have a huge bubble come out that drops the level by 2-3” in the funnel.

I don’t know that it will take an hour; but most of mine have taken at least 15-20 minutes, varying the revs from 2500 or so steady, down to idle, and back up. Elevation of the cap location is absolutely essential if you’re burping a Subie.

how do you know when u completed the work?
when revving to 2500rpm, does the coolant geyser up ?
should i keep repeating until there is no geyser when revving up and idling.
yesterday there was no bubble in idling anymore, but after revving high it tend to geyser up and spill everywhere (i was using small funnel, gonna buy the lisle funnel kit tomorrow )
 
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