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Install aftermarket radiator (Koyo racing rad), and flush the coolant

64K views 50 replies 35 participants last post by  JAYNESS the Great 
#1 · (Edited by Moderator)
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 up here and there, and there are likely better ways of doing things, so be warned. :)

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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.




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.




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.


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 ended 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 adjust the instructions.

Cheers!
TLP
 
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#6 · (Edited)
Re: How To: Install aftermarket radiator (Koyo racing rad), and flush the coolant

Great write up. ALways good when there are no leaks to be found after your done.

One thing though for everyone that does not own an 06-07 vehicle. When installing a new radiator. I would suggest flushing the system to get the old radiator fluid out before putting new in. Of course this depends on how long it has been since you flushed your system last. Since this is an 07 he didn't need to do it although it is advised but not needed. If your car older then an 06 and never had a radiator flush I would definately advise to do so before putting new fluid in the car.

How to do this you say. There are many ways to do it. One is having a shop do it not adviseable since you are changing out the rad anyway. Just take the hoses off the old rad after you drained it. Place a water hose in the top rad hose an turn it on. Let the car idle for aprox 2-5 minutes. There should be no more old anitfreeze in the system.
Plug the hoses with a clean rag. And get out the handy dandy air hose with a blow nozzle and blow everything dry. Or close to it. Clean up your work station and Your free to continue the install.

As for the flush water you can put it into a 5 gallon bucket and poor it into milk jugs later on. Since all antifreeze is bio degradeable now adays it's not a huge problem for the ground. I usualy catch the first two gallons and let the rest run off. Thanks Jeff
 
#10 ·
Re: How To: Install aftermarket radiator (Koyo racing rad), and flush the coolant

nice, did you shop around for a better price? If so shed some light.
Was that directed at me? I assume you're asking where I got the Koyo? eBay: KOYO 53mm RADIATOR 03-07 Subaru Impreza WRX/STi R2704 - (eBay.ca item 280192738959 end time 14-Feb-08 21:19:20 EST)
You want the R2704 - that's the upgraded rad (not the OEM replacement).

That's $100 cheaper than anywhere I found on IWSTI or NASIOC.

Great write up. ALways good when there are no leaks to be found after your done.

One thing though for everyone that does not own an 06-07 vehicle. When installing a new radiator. I would suggest flushing the system to get the old radiator fluid out before putting new in. Of course this depends on how long it has been since you flushed your system last. Since this is an 07 he didn't need to do it although it is advised but not needed. If your car older then an 06 and never had a radiator flush I would definately advise to do so before putting new fluid in the car.

How to do this you say. There are many ways to do it. One is having a shop do it not adviseable since you are changing out the rad anyway. Just take the hoses off the old rad after you drained it. Place a water hose in the top rad hose an turn it on. Let the car idle for aprox 2-5 minutes. There should be no more old anitfreeze in the system.
Plug the hoses with a clean rag. And get out the handy dandy air hose with a blow nozzle and blow everything dry. Or close to it. Clean up your work station and Your free to continue the install.

As for the flush water you can put it into a 5 gallon bucket and poor it into milk jugs later on. Since all antifreeze is bio degradeable now adays it's not a huge problem for the ground. I usualy catch the first two gallons and let the rest run off. Thanks Jeff
Good call Jeff - I didn't need to do a full flush simply because I already had my coolant fully flushed last summer (major install) so I was already on new'ish coolant.

Very good point though - I'll add it to the How-To. :tup:

Awesome job Matt....I will def read this out when I do mine. Any more pics of the "cutting" you had to do to make it fit? Thanks for a great writeup, it looks mad easy, just time consuming, how long did it take you?
Thanks Chris. It is super easy... just irritating trying to fit the bigger core. Test fit, see what's in the way, cut or adjust, test fit again... etc etc.

The only cutting I needed to do was here:


Just cut those tabs off (the lower middle one will interfere with your headers), and you're good to go.

i always wondered if this was a worthwhile mod... im interested to see your findings
It definitely is... for big turbo setups that will see a lot of track time. And it seems that the '07s are in need of a better radiator for added cooling from what I've read.
Anyway, this is more preparation for my big turbo and longblock build, so I figured I'd do everything possible to make it as safe as can be.
 
#8 ·
Re: How To: Install aftermarket radiator (Koyo racing rad), and flush the coolant

Awesome job Matt....I will def read this out when I do mine. Any more pics of the "cutting" you had to do to make it fit? Thanks for a great writeup, it looks mad easy, just time consuming, how long did it take you?
 
#11 · (Edited)
Re: How To: Install aftermarket radiator (Koyo racing rad), and flush the coolant

A couple of pointers.

Unclip the passenger side fan and then remove the two ten from the top. now you can pull the fan out without having to pull the radiator. This will give you plenty of room to pull the stock radiator out.

Then i left the driver side fan in the car. That lower connector is PITA to get to. Undo the upper clamp then remove two 10mm that hold driver side fan. Then remove the radiator. This made installing and removing the radiator much easier.

If you take off 3/4 inch off the top radiator hose, the hose fits perfectly and you don't have to worry about the hose swelling and touching the pulley at all.

On my 04 STI i didn't have to cut any plastic at all. With the fans put on after i test fitted the radiator everything fit.

The PITA is the stupid drain valve that KOyo uses. It has a very POS rubber grommet that i'm not sure does crap but leak. I went back with teflon and tighten the grommet further. BTW- you can get a 15mm box wrench on it and much easier to get to if you pull the ps tank up.

I toss those POS subaru 10mm and went with toyota 10mm bolts that fit perfect. I also replaced two clamps and if i had to do it again i would have replaced all 4. Those stock subaru clamps are POS I can't believe they use those nut/washer type clamps.

After doing this and flushing my radiator, i pray to never take the radiator out again. overall job took only 3 hrs if it wasn't for the leaky drain valve. I wouldn't put samco hoses on now if someone gave it to me. it's awfully tight down there.

Thanks,
Sid
 
#48 ·
Re: How To: Install aftermarket radiator (Koyo racing rad), and flush the coolant

Great writeup!! The OEM radiator took a dump all over the engine bay last week so I installed the updated Koyo radiator (VH091672) on my '04 STi over the weekend and this was very helpful! The Koyo radiator I purchased came with all the bolts/washers necessary so there was no need to go out and buy replacements for the OEM bolts.

Everything fit perfectly... except for the placement of one of the holes on the radiator. It was for one of the support brackets on the small black pipe that runs coolant across the front. I just simply bent the bracket with some pliers and problem solved. But yeah, no cutting of the fans or hoses was necessary.

This is my first day driving with it and obviously winter won't really test it's cooling capabilities, but I'll be monitoring it. Looks great in the engine bay too!



Unclip the passenger side fan and then remove the two ten from the top. now you can pull the fan out without having to pull the radiator. This will give you plenty of room to pull the stock radiator out.

Then i left the driver side fan in the car. That lower connector is PITA to get to. Undo the upper clamp then remove two 10mm that hold driver side fan. Then remove the radiator. This made installing and removing the radiator much easier.
Very helpful tip, made removing the radiator much easier. The only thing I might add is that it wouldn't hurt to buy a gallon of distilled water and pour it through the radiator right out of the box to flush out any small metal shards left over from the manufacturing process.
 
#13 ·
This is a great write up!!! I installed my Koyo Rad today, and wasnt too bad of an install. sidwin is right about the POS fan screws, theyre like sheet metal or wood screws. I ran over to Autozone and found some M6, 1.0 bolts X 16mm that worked amazingly. I really didnt want to mess up the threats in there from the crappy stock screws! :tdown:

I did trim my top rad hose as i didnt want there to be any probs after this install was done, bottom one fit fine. I took about 1/4'' off each end, maybe like 3/8''. Put the hose back in, and it looked stock again! Enough gap on each side that the fan wont rub unless the hose swells like a mother, and that the pulleys arent any danger either. :)

Draining sucked a little too as its a kind of poor design for drainage, it went on my subframe too! Just a hint thought to help with coolant on the garage floor...kitty litter does a great job at soaking up coolant. I originally found the idea for getting oil up off the floor and it does wonders with coolant. I spread a light layer under the front end to catch splash and drips and when clean up came, no spots on the concrete! :cool:

I also did a flush of my system since I was going from Subaru's old green cooland to the new super blue stuff. And yes, its really blue! lol I did the inital drain of the coolant, squeezing both the top and bottom hoses once it drained to get any that was hiding in there. Then I closed the drain valve, and refilled the rad and filler tank with distilled water. I asked Subaru about this and said it was a smart thing to do as I was switching coolants. So full of distilled water, i let the engine get back up to operating temp and let the fans cycle 3 times to try and get some of the last green coolant out of the block. Sure enough when i drained it again, it was nearly as green as the first go. I squeezed the hoses top and bottom again, then went to remove the rad. Just helps with not getting coolant everywhere. :p

When it came time to refill with blue and burp, i did a super slow pour, squeezing the top hose to aid with the burping. After the first gallon was in, i went under the car again and squeezed the bottom hose to get it to full up some with new coolant. Then put the second gallon in, still workin that top hose. Just into the 3rd gallon it filled up, so cap went on and i filled the filler cap tank next to the intake manifold on the passenger side. Then let it run to operating temp again, and opened the cap and refilled about a cups worth. I ran the motor with the rad cap on but the filler cap off. Dont fill it full the first time cause as the air gets worked out while it runs, some coolant will come out the top and collect on the top of that little tank. I only needed to run it twice to fully burp it. After i drove around some, i still didnt need anymore! :D

Again, thanks for the write up, was really helpful to have!!!! :)
 
#15 ·
Finally I completed the Koyorad install. It was tough and took me about 4.5 hours and it was worth it. I had the most trouble putting the rad into the tight space. I didn't cut anything just put a new hose clamp on 1 tube cuz it fit loosely. I will never install a radiator again though. lol. It was time consuming cuz of the draining, flushing, waiting for engine to cool, and so on. I tried adding a pic of the radiator but don't know how. Im all cut up, burned, tired, had coolant squirted into my face. It takes patience (something I'm working on). lol
 
#17 ·
Just installed a Mishimoto Radiator and it came with all hardware needed, basically same install as OP stated, No cutting need though. Definately would trim lower and upper radiator a hair to make sure that their isnt any problems.
I also have a Beatrush cooling plate that needed to be trimmed a little as well near the cap so that it didnt rub and so that it would fit.
 
#20 ·
Very good write up. one question, did you reuse the radiator caps? (the one on the radiator as well as the one on the reservoir tank). I heard that the stock caps wont fit the koyo radiators.??? also in the Subaru service manual it says not to mix the caps (the one from the tank with the one on top of radiator.
 
#22 · (Edited)
Thanks for the How To:, I got my new Koyo Rad in the car today. Draining and flushing was no big deal. Along with the Koyo, I installed Samco upper & lower hoses, a WC Lathewerks shroud (fitted for the Koyo), a 160 degree Zero/Sports thermostat, and a 1.3 bar Koyo cap. I filled it with the Subaru Long Life Coolant (green), Subaru conditioner, DEI Radiator Relief, and enough distilled water for a 50/50 mix.

My $0.02
1. I didn't have to trim the SAMCO hoses; it's tighter for sure, but everything cleared on the first shot.

2. The stock hose clamps don't fit the SAMCO hoses, but I had already bought new hose clamps just in case so that wasn't a big deal.

3. I didn't have to trim the fans either (as per step 10 in the guide) which I found particularly strange since I also have an '07 Limited like the OP.

4. I wouldn't say the M6, 1.0 X 16mm bolts are "recommended", I would say "mandatory". Don't spend the money on a Koyo to crossthread the holes with the stock screws. New bolts are cheap, skip your morning latte and spend the couple of dollars on the bolts. (I also got mine at AutoZone) Also, grab some washers to go with the bolts. The heads started to cut into the plastic on the fans, but I was able to find some washers lying around.

5. My overflow reservoir was nasty. I wish I had one of those bristled bottle cleaners to run down in there to break up some of the caked on junk. I'll remember it for my next drain/flush/fill I guess.

6. It took 3.5 hrs, but that includes an oil change so it's probably closer to 3 hrs. I had help from a friend, so that's an advantage, particularly when trying to maneuver the old radiator out and the new one in.

My goals were 1) for the engine to run a bit cooler and 2) to have more stable temps during hard driving. I can tell #1 happened right away, #2 will have to wait until spring. :(

Thanks again for the original guide.
 
#25 ·
Are you using new OEM hoses, or just reusing the stock OEM hoses you had? If they only have about 5-10K miles on them, that's fine, but after that I would recommend new hoses completely. The heating of the hose will weaken the ends and removing the clamps and reinstalling will cause them to bulge (possibly start to seep fluid).

When I was doing the lower hose on Jayness's car, I never ended up trimming anything. The Koyo radiator seemed to fit like a glove and allowed the connecting components to do the same. Just have to use a bit of force to wedge the hose back in place.
 
#26 ·
Just ordered my radiator for my up coming track day. :)

Thanks for the pointers and the info for the fan shroud bolts.
 
#28 ·
mine went in no issue. Just cut 3/4" or so off the radiator side and they fit no problem

I'd highly suggest not using the stock bolts though for the radiator fans and shroud.
 
#30 ·
No, that's normal for aluminum radiators. They will get quite a bit hotter than steel core setups, but with the added cooling surface, they will cool faster as well. The top of the radiator will be hot due to the thermostat closing and maintaing coolant in the core to cool. Once the thermostat opens, the cooler water will rush in and lower temps of the block as hot block water/coolant rushes into the radiator.
 
#32 ·
Nah, the hot water isn't going back into the block.
The upper portion of the radiator is hot b/c that's where the coolant comes in at. The coolant that enters the block exits the base of the radiator significantly cooler. Because heat rises, hot block water enters the tops of the radiator thus, causing the upper portion of the radiator to get really hot (especially an aluminum one).
 
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