ATF leaking out the oil cooler.

[Ludy]

During a recent 4000 plus kilometer trip through a few of our Southern African neighboring countries our 4.0l V6 automatic Hilux started leaking ATF from an electric wire holder clip hole on the side of the main radiator frame. Quite a big oil mess developed on the left hand suspension parts and the left driveshaft. We analyzed the oil to originate from the autobox’s oil cooler integrated in the radiator.
This obviously was of great concern to us as we could not determine how much oil was left in the box. This model does not have a dipstick to check the oil level in the autobox. By removing the filler plug on the side of the box we could detect the oil level by pushing the small vinger down the plug hole. It seemed to be almost full. What is more we also found that the ATF that was in the box differed quite remarkably from the ATF that we purchased from the local Toyota Dealer agency. It was of a higher viscosity and had a dark green colour, whereas the Toyota oil is reddish and quite thin.
Thanks to this forum we could determine the correct filling procedure using the allen keyed plug with its vertical tube to drain the oil down to the correct level. Not being happy with the type of oil in the box we decided to do a complete oil change and got it to the correct level using Toyota supplied ATF. We carried enough extra ATF to keep filling up as the oil was expected to continue leaking from the oil cooler.
However the strange thing is it dit not leak again after the oil change and correct level adjustment.
How can this be explained?
The theory so far is that the non-Toyota service center that prepared the car before the trip firstly used the wrong oil but also overfilled by incorrectly adding oil until it flowed from the filler plug (like in the case of a manual gearbox). This caused an extra high pressure at high temperature in the intercooler and forced oil through somehow inside the cooler.
What does this sound like to the experts?
Did we also have monkeys servicing the vehicle?
Has anyone had a similar experience before with this model?
Could it have been caused by the rather deep water crossing we did? Why would the leaking have stopped after the oil change though?
Any comments will be appreciated.
Ludy.

[07luxyTD]

If its over pressuring would mean the breather is blocked and not allowing hot air to eascape or if cooled the air cannot re enter. Different brand oils run different colours and additives also. If the oil is thinner (runier) then usually should be its most likely been overworked or at the end of its service life and needs replacing. Will most likely smell off to. Could you see any cracks where the clip mounts?

Have you checked that it isnt the drive shaft seal doing the leaking and flinging its oil up. Tho there would be a distince ring where the oil is flung

[Ludy]

No obvious cracks are/were visible. The clip mount obviously in only to the frame of the radiator and does not reach the core. You have a point about the breather though. Problem is the oil that leaked out were the thicker one. The new oil very thin. Old oil looked like manual gearbox oil.(Green and thicker). The oil certainly came from the radiator. With the car stationery over night a clear vertical line of oil formed from the radiator and dripped from the standard towing loop on the front left of the chassis to the ground. Drive shaft seal was dry.
Thanks for responding. Good to reconsider some of the facts like this.
But what made it stop again? Did it perhaps leak out only to a point where the level dropped to be at an acceptable level.
Surely overfilling must be a problem. Why did Toyota go for such an unusual way of getting the oil to the right level? The filling instructions found from this forum states: "This is a special procedure that is very temperature sensitive in order to get the accurate amount of transmission fluid into the transmission."

[07luxyTD]

From my understanding Its extremly hard to get a automatatic transmission drained 100%. The torque converter would hold some fluid due to its design and so would the oil cooler. I dunno if over filling would be an isusse if its leaking from the cooler which should be constantly full there would be a crack or leak in fitting. To have it leak then stop im thinking its a minute crack and the reason for it leaking is when the oil heats up and works harder it become thinner. Since ATF has been changed have you given it a good run over some hills and made it work? Also worth rechecking if its just been filled

[Ludy]

A fine leaking crack is what I suspect as well. But it lasted the last 1500 km of the trip without leaking. That is with a camper caravan in tow. Thanks for taking an interest.