More Pink Milkshake

Long story short, which may get longer as I type this, is that I''ve been in the market for 1st gen Tundra for the past couple months. Read lots of posts about frame rust, lower ball joints, timing belts, ect. All good stuff with valuable discussions.

But when I discovered the posts about pink milkshakes, it was pretty interesting there was no real consensus of why or what factors caused it. Lots of posts about bypassing, Koyo vs Denso vs Spectra radiators, but I was still left curious as to why some get the milkshake and some don't.

My background goes back to 60's and 70's era cars I and my buddies drove an wrenched on during high school in the 80's. Everything was from the Big 3, muscle cars, sedans, trucks. But in all my experience working on cars, my family owing not less than 20 cars between 1970 and 2000, plus the dozens of friend Big 3 autos that I rode in, worked on, or knew about, never once did I hear of pink milkshake. There are hundreds of millions of cars on the road during those 30 years so my personal experience is infinitesimal I know, but I was still intrigued why it never happened to my knowledge.

So my small contribution to this forum is the following snapshots of my transmission cooler from my 2005 Impala LS 3.8 with 209,000 miles, original radiator.

TL/DR - old cars didn't seem to get pink milkshake, here's the a GM radiator from 2005 to look at.

Radiator and my shoes...



GM transmission connection is the quick-connect type



Cooler in the side tank pried away from radiator core





Close-up shot of cooler still in side tank




Quick connect unscrewed from cooler. Note the o-ring


I don't think the white residue is corrosion. It's on the black plastic tank and there were no leaks on that side. I think it's left over sealant or some other production residue.






Cooler removed from plastic tank. Not the mashed seal/oring that was on the inside between the cooler and plastic sidewall.



Inside of tank where cooler attached to.




Cooler cut in half.


Hard to see, but inside each rectangular passage was a lattice of aluminum passages the atf flows through. Picture thin alternating vee's like this [<><><><><>]





Here's a penny to give an idea of the thickness of the channel wall material.







What did I learn from this? The ATF cooler in a 2005 Chevy is pretty robust. Plus, there seems to be a concerted effort by the engineers to maximize the heat transfer between ATF and engine coolant. I read alot of threads about bypassing the radiator and the extent to which the ATF cooler can have significant impact on ATF temp is frequently derided. This cooler seems to say the opposite with all the effort put into the cooler itself. Otherwise why didn't the engineers at GM not just stick a round pipe to carry the ATF in the radiator tank and call it done?

Lastly, it seems like pink milkshake should be a pass/fail condition given how robust the cooler is. It either has an inherent defect, crack, leak that causes immediate failure or it will last forever. This makes the 7 year 90k failures difficult to diagnose. Some say milkshake is due to poor maintenance, old coolant. Maybe, but everything is aluminum, GM anyway, so what corrosion? Aluminum doesn't corrode in the presence of coolant, nor regular water. Other says electrolysis, on which I'm not expert, but electrolysis is more related to dissimilar metals in the presence of a conductive fluid. The more noble metal steals electrons from the less noble and you get pinholes and such. But again, if everything is aluminum, there no galvanic corrosion taking place.

That's all I have for now. I just thought I would share this with the community as it has been very helpful in my Tundra research. Cheers.

 

Interesting read. On the electralysis end we have aluminum heads and a cast iron block, I believe the OEM coolant is supposed to prevent any of that though.

Good stuff.

 

Very thorough post mortem. I had never heard of the pink milkshake either until reading this forum.

 

It worries me randomly now and then, just did 400 miles yesterday and the radiator crossed my mind a couple times. But feel no need to replace at the moment.

 

I struggle with this decision as well. I keep coming back to the fact that at 17 years old this one could go any minute. I'm leaning towards pulling the trigger on a Denso replacement soon.

 

A post was recently created about Champion radiators. All aluminum, tig welded, multi row, impressive. There is a vid on their webpage at https://www.championradiators.com/. If you skip to 2:45 they comment on the transmission cooler. Not sure if this is just for illustration or not, but the Champion cooler has nowhere near the engineering sophistication of the GM cooler. Interesting.

 

The round cooler is called a concentric oil cooler. It has fins within the cooler similar to the plate cooler you are calling the GM cooler. GM (and most everyone else) used concentric coolers well into the 90s. We only use concentric coolers in our radiators and have for the last 50 years. I can cut up an old cooler and post pics if you'd like.

(side note) Recently the Chinese manufactures have started to skimp on the brass coolers by using brass plated steel fins. The fins will rust if you remove the radiator and let it sit for awhile. We only use brass finned coolers in our copper/brass radiators so its a non issue for us.

 

https://www.youtube.com/embed/A19qEjCzFWY

 

It seem copper and brass radiators were the norm in old cars, but the switch to aluminum was made to save money as it sounds like the Chinese are doing with the ‘plating’ you stated above.

Seems like a solid copper radiator would be the best option, but it sure would co$t. Probably would last forever.

 

When they switched to aluminum radiators, they also went to a higher efficiency core. The tubes are closer together and there are more fins per inch (heat transfer points). Thats how all these cheap aluminum radiators manufactures justify saying "aluminum radiators cool better than copper/brass radiators". That statement, without explanation of the different core types, is very misleading. If you compare a high efficiency copper/brass core to an aluminum core (same size, same amount of rows, same fins per inch), the copper/brass will out cool the aluminum radiator. But as you say, they are more expensive up front. (side note again: Not all copper/brass radiators are equal. We've seen a ton of Chinese copper/brass radiators that had improperly baked cores. This causes a lack of fin bond to the tube so they dont cool at all.) I could go on for days about this stuff, but I'll stop here

 

This is interesting stuff and thanks for the input.

 

Sharmstr, thanks for joining the conversation. I was hoping someone with professional experience would add some real world knowledge to our discussion. You mentioned "we only use", are you with Champion or some other radiator manufacturer? If you are able, please do post some pics of the concentric oil cooler that you mentioned and please expound on why you think, or know, that Toyota, particularly the 4.7 radiators in Tundras and 4Runners seemed to have the atf oil cooler failure at a higher frequency than other brands.

It's interesting that GM moved from the concentric oil cooler to the stacked plate in the 90's as you say. GM is frequently associated with lowering their quality to pinch a penny so I find it interesting that GM would use what appears to be a more sophisticated, and costly, stacked plate oil cooler. Perhaps the demands of the more compact transmissions and radiators in the transverse mounted fwd cars demanded greater atf cooling then previous years.

There are lots of discussions on this forum and others about the stacked plate external coolers being superior to a fin and tube design (B&M vs Hayden), I'm assuming a stacked plate internal cooler has some advantages over a concentric as well? Can you educate us on the pros and con's?

 

I was trying to avoid talking too much about where I work because I didnt want to sound like an advertisement. I work for U.S. Radiator. We've been making radiators for 50 years in the USA for classic cars. I'm by no means an expert, especially with new vehicles. I say we only use concentric because we are forced to in most cases for 2 major reasons. 1 - 90% of our business is copper/brass and I've never seen a plate cooler in brass. 2 - Even if there were brass plate coolers, they wouldn't fit in most radiator tanks. We die stamp our tanks to look original, so modifying the tank design to fit the plate cooler, even in our aluminum line, will never happen.

Again, I dont have any experience with plate coolers, or modern transmissions, so I cant really speak to it. I could throw out educated guesses, but no one wants that

I can say that we have seen very few concentric oil cooler failures (even in aluminum). But we aren't comparing apples to apples here, so take that info with a grain of salt.

Here's a few pics of the inside of a concentric cooler.

 

Does your company make these for 1st Gen Tundras?

 

No. I had plans on making one for mine, but didnt get to it. 2 weeks ago my top tank gave out while on a road trip and had to get one installed at a dealership. If it would have happened closer to home, I would have made one. Figures. Anyhow, we mainly make them for 1980 and older American cars.

 

Updating with pics from my radiator replacement on my 2006 Doublecab with 165k. I shopped Denso, Koyo, Spectra, Mishimoto, and Dealer OEM. I also specifically email each of them asking about the pink milkshake problem and if they took any engineering steps to prevent it and also asked if their ATF oil cooler was concentric or stacked plate. Here are the responses of those that replied:

Mishimoto:
Thank you for reaching out to us here at Mishimoto.
We have found that when this situation occurs it is often due to epoxy being used to seal the units and keep everything together. This is something we do not do on any of our all aluminum radiators. We use a brazing process to ensure everything will have a tight seal that will not fail like the epoxied units. I hope this has given you some more information for you to make a decision.

Denso replied with no text but the following diagram:


No reply from Koyo or Spectra.

One dealer quoted me $180, next dealer $420 for radiator only. Both claimed it was Toyota OEM. I didn't want an internet purchase due to horror stories for damaged units plus my fed-ex and ups guys seem to enjoy crushing every other package I receive from Amazon so I ended up with a Denso from the local Napa for $240.

New Denso:




ATF connections:



Here's the original 2006 165k radiator





OEM Cooler is stacked plate, which I find interesting because all material online for Denso, Koyo, Napa, Spectra all say concentric 1" or 1.25"

 

Are you using the old cooler? I would start with a fresh one now.

 

https://www.tundras.com/threads/install-complete-on-additional-transmission-cooler.12385/

 

Here's the rest of the pic's.










As best I can decipher, the milkshake only has 2 modes mix atf and coolant. Obvious mode is manufacturing defect in the cooler, stress fracture, or whatever that after a number of thermal cycles a leak develops and coolant and atf mix. Second mode as postulated by other forums is the steel washer that is on teh external side of the tank rusts badly, the rust causes an expansion pressure to be placed on the fitting. Since the fitting is aluminum, the expanding rusty washer causes the threads to strip or stretch, which then eases the mechanical pressure on the oring on the inside of the tank. This allows seepage of coolant past the oring and into the atf circuit.

My new Denso supposedly has a concentric cooler based on Napa info.

Specifications

• Important Information: w/ Double Cab

Radiator Core Size 27 3/16 in. x 23 5/8 in. x 1 1/4 in.
Radiator Inlet Connector Size 1 9/16 in.
Radiator Make Toyota
Radiator Outlet Connector Size 1 9/16 in.
Transmission Oil Cooler Size Concentric 1 1/4 in. x 14 3/4 in.

The diagram from Denso above didn't load so here it is again:


Interesting is that Koyo website lists A2376 as the Koyo part# for my truck which is shown in the Denso diagram middle right "Supplier P/N". Spectra also uses p/n 2376



My unscientific conclusions:

• There is probably only one major radiator manufacturer that sources Denso, Koyo, Spectra from China, Taiwan, Indonesia.

• My old radiator was quite healthy other than the rust starting on the ATF cooler barb.

• My new radiator is probably close to OEM, and barring any initial manufacturing problems should provide decade or more if trouble free life.

• I think I now have a concentric oil cooler that is not as efficient as the stacked plate, but the connection on the new Denso, threaded bard into another barb should prevent failure mode #2 above. If the rust expansion dislodges the oring, I just get an external coolant leak, no mixing with atf.
• I also think there is only one manufacturer of concentric oil coolers that supplies to the radiator manufacturer(s). Hopefully it's actual brass, but the barbs lead me to believe it's just steel and the engineers are relying on the coolant anti corrosion protection to prevent a leak in the cooler.

 

Thanks for the great write up and pics. I too have been researching a replacement radiator for my 2002. Despite my recent bizarre encounter with a Denso engineer it seems they still make the best replacement radiator for our trucks, based on reviews.

Question for you. How did you decide between Denso part # 221-0517 and the one you purchased 221-0518. Several people have asked what is different and I've not found an answer. Both seem to work.

Amazon sells 221-0517 which seems to work fine but several people report that mounting clips didn't line up correctly and required some redneck ingenuity. Did you have this problem?

$165 Denso 221-0517 Radiator

https://www.amazon.com/dp/B0049GHV3...olid=1ZCWOVJG07GWJ&psc=0&ref_=lv_ov_lig_dp_it

 

FirstGen, I didn't encounter that part number because it's not spec'd for my Doublecab. But my Napa Denso did have the same looking mounting flanges with the extruded u-nuts that did not line-up very well. I ended up swapping the mounting flanges from the old radiator onto the new one. Only one bolt at the top and bottom on each side, you can see it just by the filler neck, to keep the original flanges that line up perfectly.

 

The mounts seem to be the biggest complaint on all the reviews, be it an aftermarket or OEM.

 

A timely thread. Last night while trying to figure out how to kill DTRLs and ABS I discovered a crack in the top plastic of my radiator was leaking.

I ordered that same Denso radiator off Amazon as it seems the closest to OEM.

Now I'm wondering if should bypass the tranny intercooler completely and just use the external cooler. Anyone doe this? Pros, cons? Would really kill me if I had to replace my transmission any time soon.

 

I'm not the pro but I don't think that's necessary. Stay on top of your fluid changes and check the trans dipstick regularly and you should be fine.

Which Denso part # did you use?

$165 221-0517 Radiator

221-0517 or 0518?

 

$165 221-0517 Radiator

221-0517. Amazon says that 0518 does not fit my truck.

From reading reviews it seems the 0518 is for Sequoias but can be made to fit Tundras with a little modification.

 

The radiators crack internally and mix the tranny fluid with the coolant and bam pink milkshake. The current gen of frontiers and the the older pathfinders on the same platform were famous for this. The water ends up eating the solenoid packs and you’re out many thousands of hard earned dollars.

I am a huge fan of separate coolers. The dodge vans mix the a/c and trans cooler.... I swear engineers hate mechanics.

 

Separate coolers are one thing....but I can't help but wonder if the intercooler has a more important function of heating and regulating temps rather than just cooling.

Does anyone know if the external cooler comes before the radiator or after in the fluid flow. If it comes before then I suspect the system is designed so that it can dump extra heat, and the intercooler raises or lowers temp to spec regardless of ambient temps since coolant is thermostatically controlled.

If the external cooler comes afterwards then its just dumping heat on the return path to the tranny and it doesn't matter what the temp is.

Anyway, I like the idea of using the external cooler, but worry that the intercooler has an important function of its own.

I mean, the engine is supposed to be at a certain temp regardless of wether its 110º outside or -50º, it seems the tranny would be the same way.

 

Just to add this, mishimoto makes a “plastic free” radiator completely of aluminum. I personally haven’t used one but people that have seem to love them and their warranty.

 

It is my understanding that it is a cost saving measure.

My tow truck for instance is a 2017 f450 and the trans cooler is a separate unit on those cab and chassis. On the lighter duty (consumer) ford trucks it is my understanding that this is not the case.