Having gone through the milkshake, it blows my mind this is even a debate. Yes, you should absolutely buy a new radiator... and bypass it.

The answer to this question is always 'Yes' when you have a fresh radiator. Your choice.


Edit - since I have been running a Tru-cool in series for a year and have a 1.5 year old radiator, I think I'm going to plumb it to bypass and see what the temp change is on my UltraGauge, if any.

Or, you know, take care of your truck. I replaced my (original!) radiator around 2017/8 around 270k miles. I took apart the bottom tank and cooler - 0 corrosion present. Funny thing - when you keep up on your fluid changes (rad and trans), you don't get internal corrosion that leads to the pink milkshake.

I now have a big enough secondary trans cooler (with thermostat) so I probably don't need to use the radiator cooler anymore - but maybe using it for power steering instead might be helpful.

-Charlie

I added external cooler in series before and after my new radiator.

I found out without it, in stop-go Austin May-Oct 100+ weather while towing, the radiator alone would not keep trans below 200 (sometimes would hit 215) so back on the internal radiator circuit and voila, well under 200 at all times now.

As others said, just keep the toyota red fresh. Your cooling may vary.

Every three years I drain the Rad and top it off. Keeps it fresh and I don’t have to deal with draining the block and potential air pockets…


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My mistake was "taking care of the truck". I thought I wouldn't need a bypass, being the outstanding citizen I was. Though, the rig was being pushed hard. So maybe it is my fault for not bypassing sooner.

Now, I think even a stock grocery rig needs a bypass. I would not want to think, "it's only those guys that need to bypass, I'm fine". I think this is one of those things that you just have to experience, it will magically change one's logic. Mine was well taken care of. Many people take care of their rides and still get the milkshake. Two year old radiator. Can't blame all the owners.... Maybe some.

Every 3 years? That seems like a long time... I guess if you sample the fluid out the bottom and it looks clean, no problem.

My 01 schedule says coolant drain every 120 Months, I try to remember at 60.

The toyota red coolant does say good for 'Life' or 150K.

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4RnR Maint Sched2001.pdf (7.4 KB, 45 views)

Yep most stuff is at minim 5 year coolant.


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Are you running two external coolers?

Like:
Transmission —> first external cooler —> radiator —> second external cooler —> return to transmission

No - I didn't word that very well. I meant to say I tried running without being in series (not using radiator trans cooler - only external) and my temps would rise to 215 when towing. Once I put the radiator trans cooler back into series with the external it is able to maintain under 200 while towing in stop-go traffic.

I know not everyone needs this much trans cooling yet it is what works for my situation.

And you’re running you external after radiator?

Something to keep in mind for those who live in areas that have cold winters.
At 180K I replaced my radiator and added a B&M trans cooler which I installed in series with radiator trans cooler.
This is my DD, no towing or off-road use but it does see some heavy traffic during summer months where temps are 90-95 degrees.
Northeast location so winters are cold as in low teens or single digit.
Scangauge tells me trans temps during winter routinely stay between 95-120.
I don’t think this is an ideal situation as trans fluid never gets close to “normal operating temperature” regardless of how long my drive is.
How bad it is I don’t know, maybe someone can chime in and advise.
I do a partial trans fluid exchange every other oil change.

It's not ideal for transmission wear, but it's a lot better than running 210+. When I installed my external cooler I purposely chose a large cooler with a built in bypass valve. My temps stayed pretty cold during the winter as well even though I'm in the south because I completely bypassed the transmission cooler. If you are concerned about it then I would recommend plumbing back into the in radiator cooler after the external cooler (or switching from external cooler to radiator cooler) when it gets cold out. Also, keep in mind that the temps you are seeing on the scangauge (and ultragauge) will be the hottest the fluid possible. You're probably aware of this but wanted to point that out for anyone that comes across this in the future.

My factory maintenance schedule says to replace the engine coolant every 30,000 miles or 24 months. It repeats in the maintenance schedule every 30,000 miles as well.

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