99’ 4runner transmission cooling
 

Hello,
my runner has low miles 112k but is 20 years old now, so thought a good idea to be proactive and replace the radiator with a new Denso 221 that I’m getting from Summit. Also bought the BM stand alone trans. cooler 70264. No problems with the radiator, or trans. In my runner now. But again everything looks original so 20 years old. My questions are this, should I hook the BM cooler in a series with the new radiator cooler? Or should I use the BM trans. cooler as a separate cooling system for the transmission? My mechanic said he has never seen the “strawberry milkshake” issue. I would think the transmission would stay cooler using both the radiator cooling and the external trans. cooler together, but the “strawberry milkshake” things scares me too! Hot hot Summers here, cold below 0 at times in the winter. I do some towing with a small trailer and boat, also, off-road Overlanding travel. What real use experience and opinions do the Members have on this subject? Vance.

The B&M install instructions as well as other manufacturers recommend running the fluid through the radiator cooler and then the external cooler.
If you replaced the rad and replace the antifreeze every 5 years you will not have to worry about "pink milkshake".
There are many, many thousands of vehicles that route the fluid through the rad without any trouble.

Either the original rads were defective or throughout the vehicles life the antifreeze was never changed.
In the 2cnd gen world the pink milkshake was never an issue.

Marc,
I appreciate you taking the time to respond to my questions on the transmission cooling. Some of my questioning comes from myself not having had the best luck with automatic transmissions in the past. Always still enjoying the control of a manual transmission. I always wanted a 3rd. Gen. since Toyota updated the runners in 96’. I will admit never having any problems with my auto transmission in my 97’ FZJ80. Loved that vehicle, but sold it! I really wanted a manual this time around, but liked everything about what the 99’ Limited had going for it. The one I did get is in really nice shape and want to keep it the way for a long time of use. Thanks again for your response! Vance.

My understanding is that most people who install external transmission coolers bypass the built-in radiator cooler entirely.

The transmission fluid / coolant intermix has affected enough people that I’ve replaced my radiator a few times over the years as preventative maintenance.

I’ve owned my 4Runner since new and the transmission has been utterly problem free for more than 432,000 miles. The only thing I do is a complete transmission flush every 100,000 miles using Toyota fluid.



Andreas

Thank you for your reply. The route I took is this. The radiator I bought from Summit turned out to be made in China. My mechanic had an original OEM Toyota/ Lexus new, so that is going in today, along with the new BM transmission cooler hooked up in series. I will be doing a complete transmission flush as soon as I save up some more money to have it done. Lower ball joints being done as I write this! I wanted a 3rd. Gen. for a long time. Plan on using this as an Overlanding vehicle exploring all the back roads in my State! Will be loaded up with gear and climbing grades while exploring, will have a transmission temp gage installed when I have the transmission flush done. All the above except the BM cooler is all with Toyota factory parts, radiator hoses, rad. cap, everything. Vance.

Looks like you've got a good plan there.
In series is what the cooler manufacturers recommend.

I have to admit, I was disappointed that Summit sent me the China version of the Denso 221 radiator. I have bought many items from them in the past and been happy. I know they want to put out the best price possible, but come on, why not the best price with the best products? Okay, done with my rant! Living where I do, is Four true seasons, cold winters with lots of snow, hot summers with 2 months of 90s-100s temps. I live at about the 2000’ level. Then loaded down with camping and off-road gear, I wanted to make sure the runner will be as dependable as I can with good maintenance and Toyota or better parts when I replace or repair anything. Still have the factory bumpers and running boards. But that will be changed out as money is available. Maintenance first, buying a used vehicle I went through items to insure a dependable vehicle. Next up, timing belts and water pump, then transmission flush and transmission temperature gage. Then Factory running boards will come off and good rock sliders, for rocker protection. Bumpers after that. Staying with stock size tires and no lift for now. Want to have my full plan on the build before adding bumpers and more. Even for now, will go with bolt on rock sliders tell I decide on lift for my intended use.

I traded in a 2010 Jeep JK Rubicon, for this 99’ 4Runner. The Jeep had low miles, but with my health issues, road to stiff and was beating me up when even going up my dirt road to my property. I have a Jeep Cherokee, with a diesel Mercedes Benz 5cylinder motor with lots of other work and mods done to it. Will be selling that if I can get most of my money back out of it. Also, a 99’ Dodge 2500 Cummings 4x4, that I use for truck things and hauling my 10’ Alaskan pop top camper. The camper is old, 1965, but in great shape. Have myself spread out a little to much, so, Jeep will have to go! I have had 5 Toyota’s in the Pass, so, New what I wanted this time around. Glad to be on this forum and hope to help others and learn all I can too. Thanks everyone for helping with my questions! Vance.

Here is the radiator you want! $164.00 from my local dealership. Been in now about a month and 2000 miles later over ruff roads, some of the miles are from my trip on the WABDR. I did also add the BM transmission cooler in series, radiator- BM cooler- then back to transmission.https://cimg3.ibsrv.net/gimg/www.yot...4ddce8c1b.jpeg

Have an appointment setup with my local Toyota dealership service department to do a transmission flush, this Friday. All is working well, just preventative maintenance. Vance.

not entirely. i just asked on t4r and i actually found out a lot of people still run the external cooler in line with the cooler inside the rad itself. they claim its the best way to keep your trans cool.

personally, when i do this mod, i will not be running anything through the radiator (other than coolant). i do not want even the slightest chance of a pink milkshake incident.

Im with Andreas on this, if you are going to the effort of improving and eliminating Toyota’s originally flawed design of a shared compromised radiator with a stand alone unit, why would you continue to use the troubled radiator? Just make replacing radiators a wear/service item every 75k miles.

I use a separate cooler. I don’t continue to flow thru my radiator. If the radiator fails with just coolant, my temp gauge will alert me. If the radiator fails and contaminated the transmission fluid, at all, it’s too late.

It's not a flawed design. Millions of vehicles of various makes do it this was.
These trucks are 20 years old many with unknown maintenance history.
Install a new rad and change the antifreeze every 3-5 years and don't worry about it.
The transmission cooler manufacturers recommend running it in series after the rad. Probably for a good reason. Like they work better in general.

Except pink milkshake started happening when 3rd gens were only 7-10 years old. This was clearly and issue with the radiators, the material it was made from, a design flaw, an incompatibility with the antifreeze or transmission or some other inherent issue. Yes thousands of vehicles use a shared design. But SOMETHING was wrong with 4Runners that caused such a systemic contamination failure.

If it was that big of a problem, there wouldn't be thousands upon thousands of these 4runners and Tacomas still on the road running the stock setup.

Maintain the cooling system and you will never have the mixing problem.

When using an external cooler in series with the rad then I would make the flow through the cooler-rad-transmission. There are two benefits to this. The first is the hot transmission fluid dissipates as much heat possible before going to the radiator thus putting that much less heat into the cooling system. Second, is during extreme cold ambient temps, the trans fluid can possibly get below optimum operating temperature. If it goes through the radiator last, it will help bring the temp back up closer to optimum, assuming the engine coolant in the rad is hot at the time.

Most if not all cooler manufacturers recommend Rad/Cooler/Transmission. Why second guess them?
In Northern climates in city driving less than 10 miles or on the highway, the transmission fluid never gets much past warm and there are no failures because of that.
At -30 and a short trip the fluid never gets past 100 degrees. Many thousands of vehicles do this every day in the winter.
A good cooler will bypass a bit anyway when the fluid is cool.

Quote from the B&M instructions.
"Route the transmission fluid through the stock
radiator cooler, then through the supplemental
B&M SuperCooler and then back to the
transmission. This will provide the most efficient
transmission fluid cooling system for your vehicle."

look, i think its a stupid idea to continue to use the cooler in the radiator when you have an external cooler. im just stating what i see on t4r.

from what i gather, some people want the absolute maximum trans cooling for their 3rd gen (ie for towing). this is achieved by putting in an external cooler, and utilizing the stock trans cooler. there is no doubt that is the best way to keep your trans as cool as possible. i just think the OEM design is a terrible design (despite how many other cars utilize this design, still terrible!).

another thing i think some people dont keep in mind is something Marc touched on. i just bought a 99 limited. i have no idea how many miles are on the coolant and radiator. im not going to keep track of how old my radiator and coolant is. it gets a visual check every time the hood gets popped. im also certainly not going to run out and buy a new radiator when mine is perfectly fine. what if you buy a new radiator and its defective right off the bat? now you have a potential pink milkshake issue that you just opened yourself up to.

what i am going to do though is ensure that pink milkshake NEVER happens on my rig. whats the easiest way to do this? external trans cooler with block off on stock rad. i dont care how 'rare' or 'infrequent' this happens, i dont ever want this to happen to me and this is how i will prevent it.

edit:
while im thinking about it, i find it hilarious how the majority of the users on here think its a terrible idea to keep routing ATF through the radiator when you have an external cooler (myself included). on t4r its almost the complete opposite. lots of people keeping track of 10 years for a radiator and 3-5 for coolant (which is absurd IMO when its a ridiculously easy work around).

Regarding this point, our radiators have plastic caps, which degrade and fail with age. I've seen a radiator hose being removed on a 17 year old 4Runner, with half the plastic outlet coming off with the hose. And the radiator "looked" perfectly fine on the outside, so I don't think you can check a radiator by looking at it. The Lexus and Toyota mechanics I spoke with recommend replacing these radiators every ~100k miles or 10 years.