Good morning, Enthusiasts.

2003 E350 Super Duty. 5.4l gas engine. 4R100 tranny. 120,000 miles. The vehicle has a Minnesota body - slowly falling to pieces because of our road salt.
Everywhere I look the engine and frame parts are more rusty than any of my previous Minnesota vans, even those with twice this mileage.
The fittings off the main radiator for the tranny cooler lines are a bit rusty but show no signs of leaking.

I recently changed tranny fluid in this vehicle (within 2 months). I followed Mark Kovalsky's instructions and used Mobil1 synthetic fluid.
The shudder at overdrive disappeared immediately and the van is shifting VERY well. Thanks for the instructions, Mark!
(By the way, I ordered the Mobil 1 from Summit Racing. Best price I found anywhere.)


Though this van is a rust bucket it has had no leaks until now.

2 weeks ago I noticed a small amount of red fluid dripping from the front of the engine. I chased it down (something of a challenge as there is never much) and found
it coming off the plastic bottom of the radiator. Note: The leak would produce a driveway stain of about 10" x 10" during a work day (on my customer's driveway - aaarrgh!).

This was after I had degreased all the cooling assemblies - main radiator, AC coil, power steering radiator, and tranny radiator - as well as the bottom of the engine, all the coolant and tranny hoses, and all the front frame and suspension parts. I did this because I was finding it impossible to locate the source of the leak.

The very slow leak seems to come from the joint between the metal part of the main radiator and the plastic bottom that - as I understand - houses a coil of pipe for moderating the tranny fluid temperature.

I have looked all around from above and below and can find no place where tranny fluid or power steering fluid might be leaking and spraying onto this area.
Since I've degreased everything there are no leaks showing up anywhere except at the bottom of the radiator.

The fluid coming out is clean red fluid like new tranny fluid - no milkiness at all.

As I've been reading on the issue I've heard dire warnings about tranny leaks inside the radiator wreaking havoc on the tranny.

So, yesterday I disconnected the tranny lines from the radiator and bypassed it altogether. I capped the tranny cooler taps on the radiator with a short section of tranny cooler hose.

So far today, after a bit of driving, there are no more signs of a leak at the bottom of the radiator - or anywhere else, for that matter.

There are no signs of milkiness in the the tranny fluid at the dipstick, and when I was pulling hoses off and on yesterday the tranny fluid that leaked out looked perfect to me.


Now for my questions.

1. Is it ok to run the van with the tranny lines bypassing the main radiator and cooled only by its own radiator? I don't regularly tow with this and when I do it's a just a 4x8x2' tall junk trailer.

2. What kind of leak would there be in the bottom of the radiator that would ooze tranny fluid from the metal-to-plastic joint but not - at least apparently - adulterate the transmission fluid?

3. How do I test my coolant for transmission fluid? The coolant is a little red, but as I recall the last coolant I added was red.

4. How do I test my transmission fluid for coolant? I don't want to throw out $180.00 worth of Mobil1 ATF if I don't need to.

 

The radiator needs to be replaced. My concern would be coolant in the transmission more than transmission fluid in the coolant. Water ruins automatic transmissions.

The auxiliary cooler should not be used by itself. You should really run the main cooler in the radiator.

The transmission fluid will will look like a strawberry milkshake if the level of coolant gets high enough, but at that point it is too late and the transmission will most likely need a rebuild.

 

Thanks for the reply, 98-.

Looks like I have a radiator replacement in my future.

I will keep my tranny cooler lines disconnected from the cooler in the radiator only until I get the radiator replaced.

The tranny fluid "LOOKS" perfect. No milkshake appearance at all. Is there a way I can test it to confirm that it is still good enough?

 

Update to the thread:

I've not had the chance to install a new radiator yet. I did bypass the in-radiator cooler as described above.

I had degreased the area thoroughly so I'd be able to easily find new evidence of leaking, at the radiator or any where else near anything associated with the tranny cooling system.

I've been keeping an eye on the underside of the radiator and surroundings and the tranny fluid is still oozing from somewhere.

Yesterday I confirmed that the AC coil (right behind the tranny cooler) is pretty well coated with tranny fluid ( I missed this before) and was able to finally notice from below that the back of the tranny cooler is very wet with tranny fluid, as is the passenger side tranny cooler hose. I also noted that the tranny cooler mount on the passenger side is broken (likely rusted through), so it's hanging free there and I imagine, wobbling in the wind every time I drive.

As I see things now the tranny cooler leak has been the problem all along. When I drive highway speeds the leaking tranny fluid is blown back through the AC coil and the radiator. Some of it collects on the radiator and runs down to the bottom when I stop driving. This fluid flows across the part of the radiator where the tranny lines run and has, up to now, left me thinking tranny fluid was leaking out the bottom of the radiator.

I've ordered a new tranny cooler from Amazon and should have it by the end of the week. I'll replace that and then we'll see what we see.

Off to work.

 

I was able to finish the project (I hope!) this weekend.

The new OTA (oil to air) tranny cooler is installed and the hoses are reconnected to the OTW ( oil to water) cooler in the radiator.

The OTA old tranny cooler support brackets and frame were so rusted they partly fell apart in my hands. The 2 bottom mounting bolts had to be cut off with the Dremel due to rust. The cooler itself was not leaking in any one particular spot but seemed to be just slowly oozing ATF all over the 4 or 5 top 'layers'.

I degreased everything around the AC coil, the radiator, and the OTA tranny cooler after the installation. So far (two days later) there is no sign of any transmission fluid leaking anywhere.

 

One other surprise in the project- the sealed-beam headlight connections were both so badly corroded together I had to replace both connectors and both bulbs.

I've lived in Minnesota most of my life and seen a lot of rust, but never this amazing corrosion in so many of the electrical connections.

 

This is hopefully my final comment on this project.

Replacing the OTA tranny cooler has taken care of the problem for me.