94 740i oil in water

[shogun]

Is there a possibility on the 740 as on my 750 that trans fluid can mix with the coolant when the radiator breaks? On my 750 the radiator has a section for cooling the ATF.
Start with the engine cool and have your car parked on level ground. Check for Coolant inside the Engine
When coolant mixes with oil inside the engine it will created a milky goo or chocolate milk as some will call it which is a milky white or yellow colored oil. This can be seen when you remove the oil dipstick or the oil fill cap on the valve cover. You can also use a flashlight to look inside the valve cover to further inspect for coolant in the oil. There could be a very slight amount of milky oil on the oil fill cap due to condensation but this will not be present on engines that are run on a regular basis. When this condition occurs the most likely cause it a blown head gasket.

[Chuckcon82]

There is no water in oil theres oily stuff in the water reservoir but not in oil

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[shogun]

what is the color of the oil in the water? Can you figure out if it is engine oil or ATF?
Do you use water wetter? https://www.bimmerforums.com/forum/s...at-s-the-cause

[Chuckcon82]

Yellowish brown could be tranny fluid someone else said i dunno tho

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[unity]

Yellowish brown? Pics might help. But if its what I think it is, its not oil but a well-known by-product of the coolant.

[shogun]

Could be old, rusted fluid inside the cooling system. If its rusty you need to flush it and replace with new coolant with active anticorrosives, likely brown coolant was just water or mostly water.

[Chuckcon82]

Its really thick milky brown it has new radiator dont have pics i flushed it cpl times dont really drain good cuz the thick stuff wont drain ill fill it back up see if still the same and is there any way to put tranny fluid in the transmission you know

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[shogun]

The 740 has a 5HP30 without dipstick, that you have to fill from below at a certain temperature and procedure, see here https://www.europeantransmissions.co...ansService.pdf
Trans fluid you can probably use for example the CASTROL TRANSMAX IMPORT MULTIVEHICLE, Recommended for use: Honda, Acura ATF Z1, DW 1 (except in CVTs); Toyota, Lexus Type T, T-III, T IV; Nissan, Infiniti Matic J; BMW LT71141; Mitsubishi Diamond SP II, SP III; Volvo all specfications

double check on your trans the ZF label, green or black label. https://aftermarket.zf.com/remotemed...pdfc-5hp30.pdf

[SergeBMW]

How long ago did you replace the radiator?

[Timm]

As Erich has said, that is sure to be a radiator failure - the V8's have a transmission oil cooler inside the main coolant radiator - and if the internal oil cooler fails the transmission fluid ends up in the coolant.

The most serious point is that the coolant ends up in the transmission so you must replace the radiator and flush and replace the transmission fluid....

[shogun]

o.k., Timm confirms my post #2 that the radiator has a trans oil cooler inside the main radiator and if the internal trans cooler fails the trans fluid ends up in the coolant.
To flush the transmission, here is a DIY the shogun method https://www.bimmerforums.com/forum/s...ns-flush-setup
Just replacing ATF fluid the standard way, leaves 2 third of the ATD in torque converter, trans coolong lines and the trans, you have to flush the system.
Shops can do that with special equipment, but first you have to replace the radiator.
Here just for info where the connections are on the radiator for the internal ATF cooling on a 750 http://bmwe32.masscom.net/sean750/ra...eplacement.htm