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Old 02-08-2008, 02:24 AM   #1
squashman
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Default Koyo radiator install and coolant flush - How To

I ordered the Koyo Racing Radiator a couple weeks ago and it arrived yesterday afternoon. Today was install day.

I took a bunch of pictures during the install so I figured I'd post a How-To for those wanting to upgrade their stock radiator to a better cooling, higher performance radiator for big turbo setups.

This isn't the end-all-be-all of radiator installs, so don't read it as bible - I probably screwed along the way, and there are likely better ways of doing things, so be warned. If you guys see something that makes you go ... ... ... post up and I'll adjust the instructions.

Here we go...
-----------------------
Koyo Racing Radiator - part number R2704




Step 1 -
Get front of the car in the air.

Step 2 -
Remove undertray - a few bolts and a few snap clips

Step 3 -
Remove your radiator cooling panel (if you have one) and/or remove the two metal brakets that attach at the top of the radiator.


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Old 02-08-2008, 02:24 AM   #2
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Step 4 -
Remove both radiator caps - the cap on the radiator itself, and the reservoir cap.




...hate winter... look at the grime under the cap:


Step 5 -
Drain the coolant (obviously have something to catch the coolant as it drains):
  • There are two methods of doing this:
    • 1) Unscrew the pet**** valve and drain from the lower passenger side of the radiator (picture looking from passenger side, looking straight down on radiator), or;
    • 2) Remove the lower driver side radiator hose and be ready for the wild coolant rapids to come thundering out (sorry, not the best pic - looking up from the underneath the car on the driver side)
- one thing to note is that when doing the pet**** drain method, ideally you'd have a hose of some sort to keep things clean. In my case, :tdown:, I let the coolant drain over the subframe and into the basin I had waiting. It made for a smoky first start up.

Step 6 -
Now that the radiator is drained of coolant, time to get it ready for removal.
- Remove all coolant lines going into and out of radiator (not all shown in pics):






Step 7 -
Unclip wiring harnesses for radiator fans, one on each side of the rad.


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Old 02-08-2008, 02:25 AM   #3
squashman
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Step 8 -
Remove radiator. This is simple enough but will require a lot of wiggling, pushing, pulling, and finessing to get it out. Having the battery out as well as the coolant overflow tank would help, but I didn't need to.


OEM radiator out:


OEM vs Koyo (bigger and thicker ):




Step 9 -
Transfer rad fans to new radiator. I used the OEM bolts - some people encourage buying new M6 (IIRC) 15mm bolts instead of reusing the stock bolts since they're like sheet metal screws. I was fine using them and everything went smoothly.
OEM setup:


Transfer to Koyo:


Step 10 -
Install Koyo. Pretty much the opposite of removal. It's a lot thicker than stock so it makes clearance a bit tighter and getting in a bit more difficult too. I had to cut off a few plastic pieces that jutted out of the OEM fans since they were in the way of either the coolant overflow tank or the pulleys and motor.

Last edited by squashman; 02-08-2008 at 12:52 PM.
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Old 02-08-2008, 02:25 AM   #4
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Clearance between rad and pulleys:


Step 11 -
Re-install all coolant lines and hoses as they were setup originally.


Step 12 -
Add coolant mix back into the rad. I followed the [50:50 Subaru coolant: distilled water] mix plus the Subaru coolant additive since I'm in full on winter. I need the antifreeze :tdown:.
- Leave both radiator caps off.
- Pour coolant mix slowly into radiator slowing using a funnel (the slower you go, less air bubbles from bubbling).
- While doing this, squeeze the top radiator hose which will also burp the system a bit while pouring.
- When the radiator is full (the Koyo took about 7L+), fill the coolant reservoir.

Step 13 -
Burp the system. With the caps off, start the car.
- The coolant will bubble and "burp" and foam which is what you want since the air is being purged from the system.
- Revving the motor to 2k was also recommended from the Subaru service manual and forum threads.

Step 14 -
Once the system is burped, add coolant to the radiator and the reservoir so that they're both full.

Step 15 -
Reinstall upper radiator supports, radiator cooling panel, and enjoy the 20-30% higher cooling factor of your new racing radiator

Issues I had:
1) The mess. I really should have had a hose of some sort attached to the drain valve so the coolant would drain through there and not all over the subframe. Sadness.

2) Radiator fan rubbing OEM top rad hose. I reused the OEM hoses even though they will end up being a bit too long. They are completely fine uncut though, so buying new rad hoses is definitely NOT a necessity.

Anyway, on first start up, when the rad fans finally kicked in, I thought my motor seized. The sound was like a thousand cats screeching hells fury. It was actually just the passenger side radiator fan that was jammed against the OEM top rad hose since 1) the new rad is thicker so there's less clearance and; 2) the OEM hose is too long.

With some adjusting and the use of a zip tie or two , everything is perfect.

Performance:
It's 0*F here... I don't think I can give a fair opinion of the increased performance in this kind of weather. I'll know more when it's strapped to a dyno.

Let me know if and where I screwed up, and I'll edit the instructions.

Hope this helps someone
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Old 02-08-2008, 02:29 AM   #5
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awesome just ordered mine today!
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Old 02-08-2008, 09:45 AM   #6
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great write up.

I would think though that the KOYO radiator would take more than 7l+. since its nototicbly bigger/thicker in size than oem. I replaced my radiator with oem unit recently and I used 1 gallon genuine subaru coolant + 1 gallon of distilled water(50/50mix), roughly 7.6l. Manual for MY02 wrx states for 7.7l of coolant.

Last edited by rexman2002; 02-08-2008 at 10:33 AM. Reason: spelling>me
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Old 02-08-2008, 11:33 AM   #7
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I used between 2.5 and 3 gallons of to fill the system after doing mine.

I would also recommend trimming the upper radiator hose. I didn't trim mine when I installed the Koyo and under power the motor flexed enough on the mounts to cause the upper rad hose to rub the alternator pulley rupturing the hose. Not what you want. I trimmed it about an inch for better clearance.

Tony
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Old 02-08-2008, 11:55 AM   #8
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Nice write up. It's good to see people taking the time to do this.
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Old 02-08-2008, 12:29 PM   #9
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Quote:
Originally Posted by rexman2002 View Post
great write up.

I would think though that the KOYO radiator would take more than 7l+. since its nototicbly bigger/thicker in size than oem. I replaced my radiator with oem unit recently and I used 1 gallon genuine subaru coolant + 1 gallon of distilled water(50/50mix), roughly 7.6l. Manual for MY02 wrx states for 7.7l of coolant.
It definitely did. I filled it with 8L pre-burp, then topped it up with another 2-3L.

Quote:
Originally Posted by Turn in Concepts View Post
I would also recommend trimming the upper radiator hose. I didn't trim mine when I installed the Koyo and under power the motor flexed enough on the mounts to cause the upper rad hose to rub the alternator pulley rupturing the hose. Not what you want. I trimmed it about an inch for better clearance.

Tony
I had to trim mine as well but for the reason of the upper rad hose interfering with the rad fan - gross noise. I'll likely upgrade to the Samco hoses though since fitment and quality will be better than OEM.

Quote:
Originally Posted by th1rd3y3 View Post
Nice write up. It's good to see people taking the time to do this.
I wish more people did write-ups on NASIOC. We need a dedicated "How-to" forum here....
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Old 02-08-2008, 12:44 PM   #10
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Nice write up..
To add to Turn in concept's comment. To prevent from any hose / fan clearance, we normally suggest all customer to trim about 1/8 to 1/4 of the upper radiator hose.
Because the koyo is slightly thicker than oem, it pushes on oem length hose in a bit.
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Old 02-20-2008, 03:52 AM   #11
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anyone have problems with the peacock valve leaking? mine surely is.

i left drive side fan in there and made it much easier fitting. didn't have to trim any of the fan. i did cut 3/4 off the top hose.

thanks,
sid
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Old 02-20-2008, 11:15 AM   #12
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should the peacock be hand-tight or torque?

thanks,
sid
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Old 06-21-2008, 08:17 PM   #13
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Just finished my install on an 05 WRX. Definitely needed to buy new bolts for the fan assembly as the R2704 was pre threaded. I did not however need to trim any of the plastic from the fan assembly. I did cut about 3/8" off one end of my Samco upper and 1/4" off the other side otherwise I would have had rubbing on either the pulley or the fan. Thanks for the write up, it was a big help.
As for the petcock valve when I drained the original it did leak so I used a little aluminium foil to guide the coolant to my bucket. I never touched the Koyo's drain plug but it does not appear to be leaking.
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Old 08-11-2008, 10:24 PM   #14
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Quote:
Originally Posted by fataldata View Post
Just finished my install on an 05 WRX. Definitely needed to buy new bolts for the fan assembly as the R2704 was pre threaded. I did not however need to trim any of the plastic from the fan assembly. I did cut about 3/8" off one end of my Samco upper and 1/4" off the other side otherwise I would have had rubbing on either the pulley or the fan. Thanks for the write up, it was a big help.
As for the petcock valve when I drained the original it did leak so I used a little aluminium foil to guide the coolant to my bucket. I never touched the Koyo's drain plug but it does not appear to be leaking.
Couldn't have worded it better myself. 04 STI does not need any trimming for the fan assembly, but definitely needed trimming for upper rad hose. Thanks to the thread maker for the write up!
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Old 09-11-2008, 02:37 PM   #15
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good wright up. subscribed, im getting mine soon.

?s, are aftermarket radiator hoses that much better for the $?
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Old 09-11-2008, 02:53 PM   #16
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Quote:
Originally Posted by patrick smith View Post
good wright up. subscribed, im getting mine soon.

?s, are aftermarket radiator hoses that much better for the $?
First of all, this was a great write-up!

One thing I didn't see mentioned so I will add my .02. I found that after replacing the radiator, the clamps did not hold tight enough on the lower rad hose. I tightened them as much as possible but they were too worn out. I finally decided to get Samco hoses since I had to pull it all out again anyway. I also had over 120K miles when I did my radiator so you may not have the same issue.

Are the Samco's worth the extra $$? Who knows for sure. Is it worth taking the risk of re-using old hoses and clamps only to find out you have to drain coolant, rip everything out, and re-do it again? Not in my opinion. Also, if you plan on using a higher pressure rad cap, the extra strength of the Samco's might be a plus.
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Old 09-16-2008, 07:38 PM   #17
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did the OEM rad cap fit the new radiator? or does it come with a cap? i would think the OEM would fit, but just checking. i have a 1.3bar cap but its OEM fitment.
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Old 09-16-2008, 09:43 PM   #18
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Quote:
Originally Posted by swalker View Post
Are the Samco's worth the extra $$? Who knows for sure. Is it worth taking the risk of re-using old hoses and clamps only to find out you have to drain coolant, rip everything out, and re-do it again? Not in my opinion. Also, if you plan on using a higher pressure rad cap, the extra strength of the Samco's might be a plus.
Yes. While tracking these cars, I've seen numerous stock radiator hoses fail at the track. The Samco are 3x as thick and pure silicone construction means better lifespan... as long as you own the car IMO.
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Old 06-30-2009, 03:54 AM   #19
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What were the dyno reports on the Koyo vs OEM radiators? I am in the market for one...probably will be buying one tomorrow....just not sure if they're worth it?
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Old 06-30-2009, 05:31 AM   #20
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Hi guys,

I've installed this same koyo radiator before (big 3 core type). But it seems that there is a smaller 2 core type which seems to cool more effeiciently thn mine. Did a comparison with a similar car as mine with almost similar mods. Only diff, he got the slimmer koyo 2 core one and it cooled way better thn mine when comparing water temps... So just a heads up, bigger doesnt necessarily means better... even the workshop shook their heads when i brought in this big koyo rad, he said i should have bought the slimmer one..
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Old 06-30-2009, 11:36 AM   #21
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Quote:
Originally Posted by 05wrx09 View Post
What were the dyno reports on the Koyo vs OEM radiators? I am in the market for one...probably will be buying one tomorrow....just not sure if they're worth it?
I don't believe it makes any difference to horsepower. I bought mine b/c my old rad started to leak and I wanted better cooling for the track. The Koyo simply has more volume and surface area in addition to being constructed completely from aluminum.
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Old 07-02-2009, 01:23 AM   #22
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I don't believe it makes any difference to horsepower. I bought mine b/c my old rad started to leak and I wanted better cooling for the track. The Koyo simply has more volume and surface area in addition to being constructed completely from aluminum.
Yea, I finally put mine in today. Now I am thinking I will need a radiator shroud cover thing because it is dang hot to the touch....much more than that crap plastic that was on the top of the old OEM one.

Took it to the track tonight and ran 1 second slower than usual. Ugh. I think I have a boost leak....
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Old 07-02-2009, 01:34 PM   #23
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This may sound wrong but that's a sexy radiator
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Old 07-02-2009, 03:58 PM   #24
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^^^sure is.

I'll most likely get one, once my second oem unit goes. Original went at 125k miles.
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Old 07-02-2009, 05:40 PM   #25
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Quote:
Originally Posted by 05wrx09 View Post
Yea, I finally put mine in today. Now I am thinking I will need a radiator shroud cover thing because it is dang hot to the touch....much more than that crap plastic that was on the top of the old OEM one.

Took it to the track tonight and ran 1 second slower than usual. Ugh. I think I have a boost leak....
Took it to Bandimere? Nice... I'm going to the CSP track on the 18th in Golden.
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