Flushing radiator

My coolant reservoir has transmission fluid in it. I am trying to figure how it got there in the first place. ???? but in the mean time I need to deal with my transmission. Im getting ready to drain it and ill have to start the truck to do the temperature check and I feel like its important to get the radiator all cleaned out before I get to that point. My question is do I have to flush it and what about any leaks that might have been the reason its in there. When I had it towed to the mechanic he said there was coolant in my transmission....not that there was transmission fluid in my radiator, at any rate I just had the tow truck company go get my truck and thats when I saw that there was tranny fluid in the reservoir ...hence the reason Im going to drain the tranmission now to see if there is actually coolant in there.

 

Bypass the rad with a separate trans cooler and/or buy a new rad.

 

Sounds like you have a failed internally radiator.

 

You need to fix the root cause which is most likely the transmission cooler in the radiator has failed thuse requiring a new radiator. Hopefully no coolant got into the transmission because that can't really be flushed out and it will kill the transmission in short order.

Once you get that sorted I've had really good success flushing what I can out with water then filling the system up with dawn dish soap and water, running it up to temp, then opening the radiator drain and sticking a garden hose in the fill and just letting the engine run like that until it's clear and all the soap is flushed out.
It may take several flushes with soap to get all the oil out.

After that I pull any radiator/heater hoses and block drains I can and give everything one final flush through, let it drain good, reassemble, and fill with the proper distilled water/coolant mix.


If the system was ran a long time like that you will likely have to replace every rubber component like hoses for sure and possibly seals if they start leaking because the oil breaks them down very quickly.

 

As said, the radiator has most likely failed and mixed coolant with ATF. I'm not familiar with Toyota automatic transmissions, but the bands in many A/Ts will fail when contaminated with water. If it hasn't had a lot of miles, maybe you're lucky and can flush it out and be ok with just a new radiator.

 

If trans fluid gets into the radiator, then coolant gets into trans. Just replace the radiator. Do the job RIGHT! Good luck.

 

For some reason toyota engineers have the engine and trans cooling system tied together at the radiator. When the rad fails, the systems get mixed. The trans fluid is more important. At last replace the radiator and hope the transmission is ok

 

Nearly every vehicle with an automatic transmission has a coolant to fluid cooler whether in the radiator or somewhere else, they don't fail often but when they do they make an expensive milkshake.
Some vehicles have an air to fluid cooler in addition to the coolant to fluid cooler but not many have only an air to fluid cooler.

I've seen engine oil coolers fail in the same way, not often but it does happen and when it does it's a mess to clean up.

 

Typically, the transmission hard lines to the radiator fail first.
They rust out.

In these trucks, it's rare to see an internal failure of the radiator/trans cooler.

 

Had a 2000 4runner before my 2012 taco and first thing I did was bypass the radiator.
They had a lot more issues.
Replace the radiator,coolant,trans filter and fluid.Maybe do one or two drain and fills after it runs a bit.