Interesting Discovery on KOYO Radiator

[BamaDrewski]

I have discovered an interesting issue with the Koyo radiator.

I replaced my radiator (With a Koyo) a couple of years ago and bypassed the radiator with a large, external transmission cooler. I did this so I would not have to worry about the infamous “pink milkshake”. I simply capped the coolant and inlet outlets at the bottom of the radiator with rubber caps.

I was under my rig this past weekend and noticed some small coolant leaks coming out from around the rubber caps on the bottom of the radiator. As I never used the transmission cooling section of this new radiator, it appears that somehow the main part of the radiator is seeping/leaking into the transmission cooling section. Clearly, something like this is happening and it gives me even more PEACE OF MIND with my bypass of the radiator. Just imagine if this small leak/seepage is happening on these radiators - even the new ones..... This would mean that there must be coolant leeching into the tranny fluid over time. With the external transmission cooler, there is NO CHANCE of this happening.

Of course, one explanation for this could be the factory filled these radiators to test before releasing for sale and in that case, perhaps the coolant I am seeing coming out of what should be an “empty space” could be the residue of the testing. I have no idea however, if KOYO fills and tests these radiators before selling. Thoughts?

 

[cashmoney]

Be simple enough. Blow air through there to dry it out and see if it continues to leak.

 

[jeremyc74]

Of course, one explanation for this could be the factory filled these radiators to test before releasing for sale and in that case, perhaps the coolant I am seeing coming out of what should be an “empty space” could be the residue of the testing. I have no idea however, if KOYO fills and tests these radiators before selling. Thoughts?

I would say that's a possibility, but you could prove it out easily enough by removing the rubber caps and making sure it's completely dry, then putting them back on and see if it comes back.

I think if it is actually seeping through you have a defective unit, rather than all of them doing it to some degree. I think we'd have a lot more transmission issues than we do, even before the full on pink milkshake.

 

[1985taylor1925]

I would say that's a possibility, but you could prove it out easily enough by removing the rubber caps and making sure it's completely dry, then putting them back on and see if it comes back.

I think if it is actually seeping through you have a defective unit, rather than all of them doing it to some degree. I think we'd have a lot more transmission issues than we do, even before the full on pink milkshake.

Yeah, there's no way a fairly new unit should already be leaking unless it's defective. Koyo is an oem manufacturer for our rads right?

I went with a denso when I replaced mine a few years back. It was more expensive, but I trust the brand

 

[jgue467]

Think Ahead

That is Exactly why anyone bypassing oem or aftermarket 3gem radiators should run an appropriate transmission hose between the in/out of the radiator!!! Again, Think Ahead! :cowboy:

 

[jeremyc74]

Yeah, there's no way a fairly new unit should already be leaking unless it's defective. Koyo is an oem manufacturer for our rads right?

I went with a denso when I replaced mine a few years back. It was more expensive, but I trust the brand

Koyo and Denso are both OEM manufacturers for Toyota, but I'm honestly not sure which one was actually installed on the assembly line. It may be one of those situations like the spark plugs where there were two suppliers for the same part.

 

[fish0281]

... Of course, one explanation for this could be the factory filled these radiators to test before releasing for sale and in that case, perhaps the coolant I am seeing coming out of what should be an “empty space” could be the residue of the testing. I have no idea however, if KOYO fills and tests these radiators before selling. Thoughts?

They would never test every single one; they'd do a sample of the entire lot, and assume the rest of the lot is good to go based on the test results. The ones they do test, if they do, would get discarded after testing. For one reason, they can't be sending radiators out the door with coolant in them, even if it is a small amount. Second, it's not good practice to sell stuff that gets tested - lots of tests of this type would be to failure. Furthermore, they would test with water.

It could be that without fluid in the transmission part of the radiator, there is a pressure differential that wouldn't otherwise be there. That could be a cause for the leak. Either way, not what you want to be seeing.

 

[jeremyc74]

They would never test every single one; they'd do a sample of the entire lot, and assume the rest of the lot is good to go based on the test results. .

That's not true. Most automotive parts these days are 100% functional tested before they leave the suppliers. The OEM hit them for huge penalties if they get a defective part on the line, so they go to great efforts to make sure everything is good going out the door.

They may do a leakdown test on it using compressed air instead of fluid, but for critical stuff like this it will be tested somehow.

 

[nevada]

pop the caps and check. is the coolant coming from inside the tube, or around it?

I have seen them leak at the O-ring at the connection on various radiators over the years.

 

[RussToy]

...They may do a leakdown test on it using compressed air instead of fluid, but for critical stuff like this it will be tested somehow.

I totally agree...I'm leaning towards testing all of them. It would be very easy to do, especially using air. They would be able to simulate the correct pressure the rad lives at...and no mess (water or antifreeze) to clean up. Think about it...that's how we check the coolent system for leaks. Air pressure.

OP...you would get a real quick anwser if you did the same...just pressurize your system with a pump. At the longest...wait 10min and you'll know if it's leaking or not. Just a thought...

 

[jeremyc74]

I totally agree...I'm leaning towards testing all of them. It would be very easy to do, especially using air. They would be able to simulate the correct pressure the rad lives at...and no mess (water or antifreeze) to clean up. Think about it...that's how we check the coolent system for leaks. Air pressure.

OP...you would get a real quick anwser if you did the same...just pressurize your system with a pump. At the longest...wait 10min and you'll know if it's leaking or not. Just a thought...

I work in automotive manufacturing, and we do leakdown tests all the time. There's high precision testers out there that are capable of doing it in a matter of seconds rather than minutes.

Most of the applications I've been around are much lower volume than a radiator, but would work the same way. The part comes down the line and gets clamped up in a fixture, and all the ports get capped. Then the tester fills it to a set pressure that's highly regulated. Then there's a couple of seconds of settling time, an initial reading is taken, and then a dwell. At the end of the dwell another reading is taken, and it either passes or fails.

The stuff I deal with are electronics modules and the test is used to make sure the case is completely sealed. Things like ABS controllers and tire pressure monitors. On those we run at cycle times under 8 seconds. I'd imagine a radiator would take longer because of the volume, but a line typically needs to produce one about every 40 seconds so it wouldn't be a big issue.

 

[BamaDrewski]

Today, I pulled off the rubber plugs while installing my Magnafine filter on the post-cooler transmission return line. About 1/4-1/2 cup of red coolant dripped out. One post mentioned the difference in the pressure (having an empty cavity in the transmission part of the rad) and I thinking this sounds plausible. Either way, I either have a defective unit or the primary coolant cavity for the engine is the issue. I think I am beyond returning it but may contact Koyo to see what they say. Thanks for all the ideas and input guys!

 

[RussToy]

Today, I pulled off the rubber plugs while installing my Magnafine filter on the post-cooler transmission return line. About 1/4-1/2 cup of red coolant dripped out. One post mentioned the difference in the pressure (having an empty cavity in the transmission part of the rad) and I thinking this sounds plausible. Either way, I either have a defective unit or the primary coolant cavity for the engine is the issue. I think I am beyond returning it but may contact Koyo to see what they say. Thanks for all the ideas and input guys!

Since you aren't using the cooler...I'd cap off the in-take and the out-put for your trans cooler. This will stop your leak. Once the cavity is filled with antifreeze, you'll be good to go. Only other choice is to replace it...again. Just a thought...

Good luck

- Russel