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2003 Forester X, 5spd,
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8 Posts
Discussion Starter #1
Hey guys, I have a 2003 X 5spd and I like driving in the mountains a fair bit. No matter how I drive, I end up getting quite hot during long hill climbs. I've tried everything from crawling up in 1st gear to just sending it. This past weekend after replacing my head gaskets (part of the original overheating problem) I and my friend driving his WRX went up a fairly steep mountain road, he drifting around corners and having a great time while I lagged behind, rapidly heating up. He has the Mishimoto radiator for his rig and never got hot. As much of my weekends involve steep backcountry roads this simply won't do, so I'm looking at getting myself the Mishimoto radiator for the XT. Has anyone else done this, or installed a different high-performance radiator? And does anyone know of a comparable cheaper option before I drop $340 on a radiator?
 

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2015 Forester 2.5i Limited CVT
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826 Posts
Are you sure it’s the OEM radiator that’s causing the over heating? Have you ruled out everything else?
 

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2003 Forester X, 5spd,
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8 Posts
Discussion Starter #3
Are you sure it’s the OEM radiator that’s causing the over heating? Have you ruled out everything else?
After three thermostats, two OEM radiators, new head gaskets, new fan switches and fans, new intake manifold gaskets, and a compression test, the only other thing I know of that it could be is microscopic cracks in my block. It runs fine and holds steady temps except for long hills (10%+ grades) at 40mph or less, where it overheats. So I'll try a high-performance radiator before I replace the engine or buy a different car.
 

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15,087 Posts
Do you know what temperature it is reaching? When I stomp on my MY'03 for steep twisties it can go up to 110C / 230F; normally runs around 88C-96C / 190F-204F. OEM radiator.
 

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2003 Forester X, 5spd,
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8 Posts
Discussion Starter #5 (Edited by Moderator)
I believe it's reaching at least 230F; I had my friend testing it Sunday and it was in between 190-203F on a logging road that was equally up and downhill. I just ordered an OBD2 scanner on Amazon and will get some exact numbers. All I know for certain is the temperature gauge gets awfully close to red and I stop before it hits red. The most recent scenario I was in where it got super hot was during a half-mile climb of a 20%+ grade at 20-25 mph in 2nd gear at 2-3k RPMs.
 

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2003 Forester X, 5spd,
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8 Posts
Discussion Starter #7
Approx. 115C / 239F would be just under the red.



What is meant by "new fan switches" ?
The electrode that monitors coolant temperature and turns the fans on and off accordingly. I might have the wrong term for it; I'm just mechanic enough to change out my own timing belt and water pump.
 

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MY05 Forester 2.5 XT 5MT
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2,659 Posts
Did you get the heads machined and used new cylinder head bolts?

The factory cylinder head bolts can't be reused but is unfortunately done by some shops to save costs, leading to head gasket failure within 20K miles of the work done :(

ARP are the only cylinder head bolts I know of for the EJ25 that can be reused.

How old and how many miles on your water pump?

It would be surprising the factory/OE radiator couldn't keep up, as it is the same used in the turbo applications as far as I know with little complaints of over heating with the type of driving you described above. My MY05 XT had no overheating while towing ~4400Lbs up and downhill, which even has a transmission cooler section in too.
 

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2003 Forester X, 5spd,
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8 Posts
Discussion Starter #11
Yes, I got the heads machined. I reused the head bolts that were new 6000 miles ago when the previous owner redid the head gaskets with the worst quality product I've ever seen (I had rubber flakes floating in my coolant). The timing belt, pulleys, and water pump are 1500 miles old and I made my friend who is an aircraft mechanic check to make sure that part was done right.
 

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2001 Forester
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1,538 Posts
I have a 2001, AT. Towed 3300lbs from Philadelphia to Austin, TX and no issues. My concern would be quality of water pump, and OEM thermostat, OEM radiator cap. And is the thermostat installed properly(orientation). The stock radiator is more than capable of handling the cooling needs if the vehicle is unmodified. In fact, my son and I just towed probably 1500lbs the other day in 95F heat and no issues.

BTW, towing the 3300lbs, is like you driving up steep grades in either 3rd or 4th. When we drove from Philadephia to Austin, the engine stayed revved around 3000RPM pretty much all day everyday for the entire trip. I drove at speeds between 50-60mph in 3rd and 4th on the AT. But usually stayed in 3rd.
 

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MY05 Forester 2.5 XT 5MT
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2,659 Posts
Yes, I got the heads machined. I reused the head bolts that were new 6000 miles ago when the previous owner redid the head gaskets with the worst quality product I've ever seen (I had rubber flakes floating in my coolant).
Unfortunately that might be your problem.

The Subaru factory and typically OE spec head bolts are Torque To Yield, so they can only be used the once as they stretch during the torquing procedure.
If you try to reuse them after they have been torqued the first time, you will never achieve the correct clamping force between the head and the block and can experience head gasket failure symptoms.
 

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2003 Forester X, 5spd,
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8 Posts
Discussion Starter #14
Unfortunately that might be your problem.

The Subaru factory and typically OE spec head bolts are Torque To Yield, so they can only be used the once as they stretch during the torquing procedure.
If you try to reuse them after they have been torqued the first time, you will never achieve the correct clamping force between the head and the block and can experience head gasket failure symptoms.
Well, if that's the case I'm going to be absolutely sick if that turns out to be my problem this time. This rig has been a real lemon and I'm running out of time, money, and patience to deal with it (college student working my way through school here). I've heard these can be great rigs but I seem to have acquired an unusually bad one. A real shame too, because I'm impressed with what it can do offroad and love the fuel economy when it runs. Hopefully, I can keep it running for cheaply enough long enough to get myself an XT or a WRX eventually.
 
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