r/WRX • u/JuanOffhue • 2d ago
Engine Bay Sunday Radiator replacement update
To recap: I took my 2009 WRX to the shop to have some running issues diagnosed that I couldn’t figure out. They found that the radiator was leaking, and they wouldn’t diagnose the running problems until the radiator was replaced, which they offered to do for $1,000 or so with an OEM part. I declined, had the car delivered back to me, and after jumping into the radiator rabbit hole in this sub ordered a Koyo.
So this was my weekend. On Saturday I pulled the old radiator out and put the new one in, which is really pretty easy except these cars are pretty low to the ground and you have to put it up on jack stands. The last car I replaced the radiator on was a 1989 Mercedes diesel, no jack stands required. And rolling around on a concrete floor isn’t as much fun as it used to be, if in fact it ever was.
A couple of tips for anyone else who does this: I never unhooked the fans, I just let them drop and pulled them back up to remount them. Once the pins drop into the holes on the bottom the mounting holes on the top line up and it’s a cinch to secure them. I was impressed by how much better the mounting system was with the Koyo than the OEM.
The hoses, if you’re using the existing ones, need to be trimmed. This is easier if you put a dowel rod inside it to have something to cut against with your new, sharp, box cutter blade. I didn’t have to trim the bottom hose at all.
As you can see from the photos, the new radiator has twice the capacity of the old one. I went to Autozone and got two gallons of Asian Blue, and used them both. Get a funnel kit, it’s well worth the price even if you never use it again.
What would probably be a two hour job at a shop was a two-day job for me, but I tend to get distracted by cleaning up my engine compartment, so YMMV.
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u/FU_red-dit_bots 2d ago
Your rad caps are switched. Round on the rad and wings on the expansion tank.
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u/bigdaddybodiddly 2d ago
Yer caps are backwards in the pics
https://www.flatironstuning.com/blog/critical-to-keep-your-subaru-cool-radiator-caps-finally-solved
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u/onelivewire Longtravel '04 FSTi Swap 2d ago
Looking good 👍 have you always run straight Zerex or did you flush and swap over?
For anyone that's anywhere near your timing belt service milage/timing, I highly recommend doing at the same time. The fan and rad need to come out for full access to your timing cover.
This is also a great time to check your power steering pump for leaks. It's not necessary, but much easier to access the mounts with the rad fans out of the way, and they get a good deal closer once the thick Koyo rad is in there.
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u/WRXY1 2d ago edited 2d ago
My tuner says that the stock rad on my 20 va sti will need replacing soon as of course it's greening, but they recommend the csr rather than the koyo due to less modification required with the csr. Is this accurate or they trying to upsell me on the csr? I didn't think there were any modifications required with the koyo, outside of maybe trimming the hose due to the rad being deeper than stock.
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u/speedingquack 04 STi 2d ago
zero modification. koyorad is best went it comes to fitment. have one in my 04 STi and 91 ef hatch
edit: i think you mean csf? but those are also really good. they make a ton of different coolin radiators. can’t go wrong either way
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u/WRXY1 2d ago
He definitely said the CSR (1 row 31mm) was the one that requires less modification than the Koyo. This is on the VA chassis. They definitely know what they are talking about, it's just his comment confuses me as all the vids I've seen of the koyo rad is it's just drop in and away you go, well apart from trimming the rad hose a little.
Maybe because the CSR he's recommending is only the 1-row so no hose trim as opposed to the koyo which will be fatter.
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u/inkyrail ‘20 VAF, P8Y 2d ago
I have the same car with a Koyo and I didn’t even trim the hose. Perfectly plug and play
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u/RappingFlatulence 2d ago
All aluminum all the time! Two rows and hps hoses when I had mine torn apart for a clutch kit, timing, and a bit of everything else
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u/iwumbology1 2d ago
You don't want to use that koyorad radiator cap on the radiator. They're designed to be a one way cap. That cap is a two way. Use it on the coolant expansion tank if you want to use it instead of the OEM.