STRAWBERRY MILKSHAKE: Radiator/ Transmission Failure (automatic transmissions only)
While it is a rare occurrence, the most notorious and costly of the known issues is by far, the “strawberry milkshake.” Also known as the ‘pink milkshake’, the cause of the issue is in the pipes in the lower part of the radiator that cools the transmission. The lines are known to corrode and allow the mixing of engine coolant and transmission coolant fluids. The root of this corrosion is from the buildup of minerals in the radiator, regular coolant flushing is a good way to slow this buildup.
When the two fluids mix, the mixture overflows into the coolant overflow reservoir with a fluid that looks a lot like a strawberry milkshake (may be a different color if you dont have TOYOTA red coolant..). If the mixture manages to return to the transmission, it can cause catastrophic damage. Often resulting in a ruined transmission. When a milkshake strikes, you will notice your transmission will not want to shift or hold a gear when moving.
-As stated above, this will only happen to trucks with automatic transmissions. This typically starts to become a concern when the truck gets to be about 8-10 years old. Or even sooner if it is a rusty truck.
Red flags:
As far as detecting one that may have already happened.. When the seller mentions anything about a replaced radiator and transmission having been completely flushed at the same time, that is a BIG sign. If it has a new or rebuilt transmission, make sure it was a dealer install or at least a certified Toyota mechanic. However, if immediate action is taken when a milkshake hits (pull over, shut down, tow to mechanic), the transmission can be saved and should be just fine after a few flushes and a new radiator.
And for predicting one that may be coming.. Regularity of coolant flushes and vehicle age are the only ways. Service records are important for this reason.
Fixes/ How to avoid:
Except for regular coolant flushes as I mentioned before, there are two ways to really avoid a strawberry milkshake. The first is to just replace the radiator before anything happens; every 8 years is a good interval to set for replacement. The second way to avoid the milkshake is to install an external transmission cooler that is separate from the radiator. This removes the possibility of the milkshake ever happening as the radiator and coolant are removed from the equation. Or, if you’re wanting to really do it right, do both of these things. The new radiator will be about $150 (Koyo 1998A) and the external transmission cooler will be at least $60 (B&M 70268).
Which method to choose?
-The new radiator is the better option, as these trucks are ready for a new one anyway with the age they are getting to.
-Those in extremely hot climates are advised to go with a bigger external cooler. The B&M 70264 is the bigger one, compared to the 70268 that most people get.
-Those who tow more than normal or wheel the truck often are advised to go with both, get all the cooling you can get! (external cooler in series with radiator cooling from new radiator)
-Even though both options will have a cold fluid bypass valve, those in cold climates are advised to at least opt for the new radiator, as it supposedly helps to warm the transmission during the first few minutes.
